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Synthesis of Functionalized Tolanes for Release of Rose Scent
by
Danielle Russell
Honors Thesis
Appalachian State University
Submitted to the Department of Chemistry and The Honors College
in partial fulfillment of the requirements for the degree of
Bachelor of Science
May, 2015
Approved by:
Michael Ramey, Ph.D., Thesis Director
Mr. Jason Selong, M.S., Second Reader
Claudia Cartaya-Marin, Ph.D, Second Reader
Libby Puckett, Ph.D., Chemistry Honors Director
Leslie Sargent Jones, Ph.D., Director, The Honors College
2
TABLE OF CONTENTS
I. ABSTRACT .................................................................................................................... 4
II. ACKNOWLEDGEMENTS ........................................................................................... 5 III. INTRODUCTION ........................................................................................................ 6
FRAGRANCES: A SHORT HISTORY ...................................................................................... 6 PRO FRAGRANCES ............................................................................................................ 8 HEXAPHENYLBENZENES ................................................................................................... 9 FOCUS OF THE PROJECT .................................................................................................. 10 SONOGASHIRA COUPLING REACTION ............................................................................. 12 PREVIOUS WORK ............................................................................................................ 15 SYNTHETIC ROUTE ......................................................................................................... 16
IV. SYNTHESIS ............................................................................................................... 19
CARBOXYLIC ACID SYNTHESIS ....................................................................................... 19 ESTER SYNTHESIS ........................................................................................................... 21 TERMINAL ALKYNE SYNTHESIS ...................................................................................... 25 DIESTER TOLANE SYNTHESIS ......................................................................................... 30
V. HEADSPACE ANALYSIS ......................................................................................... 33 GAS CHROMATOGRAPH/HEADSPACE ANALYSIS ............................................................. 33 SURROGATE MOLECULE ................................................................................................. 34 PRELIMINARY METHOD DEVELOPMENT ......................................................................... 35 RESULTS ......................................................................................................................... 36 DISCUSSION .................................................................................................................... 44
VI. FUTURE WORK ........................................................................................................ 45 FUTURE SYNTHESIS ........................................................................................................ 45 ALTERNATE SYNTHESIS ROUTES .................................................................................... 47
VII. CONCLUSIONS ....................................................................................................... 50
VIII. REFERENCES......................................................................................................... 51 IX. VITAE ........................................................................................................................ 53
X. EXPERIMENTAL PROCEDURES ............................................................................ 54 INSTRUMENTATION ......................................................................................................... 54 IODOCARBOXYLIC ACID SYNTHESIS ............................................................................... 54 DIESTER TOLANE PRECURSOR SYNTHESIS ....................................................................... 55
XI. APPENDIX ................................................................................................................ 58 GC/MS DATA ................................................................................................................. 58 HEADSPACE GC/MS DATA ............................................................................................ 61 NMR DATA .................................................................................................................... 66
3
List of Tables and Figures FIGURE 3.1 ....................................................................................................................... 9
EQUATION 3.1 ................................................................................................................ 10 FIGURE 3.2 ...................................................................................................................... 11
FIGURE 3.3 ...................................................................................................................... 11 SCHEME 3.1 .................................................................................................................... 13
SCHEME 3.2 .................................................................................................................... 14 EQUATION 3.2 ................................................................................................................ 14
FIGURE 3.4 ...................................................................................................................... 15 FIGURE 3.5 ...................................................................................................................... 16
SCHEME 3.3 .................................................................................................................... 17 EQUATION 4.1 ................................................................................................................ 19
FIGURE 4.1 ...................................................................................................................... 20 EQUATION 4.2 ................................................................................................................ 22
FIGURE 4.2 ...................................................................................................................... 23 FIGURE 4.3 ...................................................................................................................... 24
EQUATION 4.3 ................................................................................................................ 26 FIGURE 4.4 ...................................................................................................................... 28
FIGURE 4.5 ...................................................................................................................... 29 EQUATION 4.4 ................................................................................................................ 31
FIGURE 4.6 ...................................................................................................................... 32 FIGURE 5.1 ...................................................................................................................... 33
EQUATION 5.1 ................................................................................................................ 34 TABLE 5.1 ........................................................................................................................ 35
FIGURE 5.2 ...................................................................................................................... 36 FIGURE 5.3 ...................................................................................................................... 37
FIGURE 5.4 ...................................................................................................................... 38 FIGURE 5.5 ...................................................................................................................... 39
FIGURE 5.6 ...................................................................................................................... 39 FIGURE 5.7 ...................................................................................................................... 40
FIGURE 5.8 ...................................................................................................................... 41 FIGURE 5.9 ...................................................................................................................... 42
4
FIGURE 5.10 .................................................................................................................... 43
FIGURE 6.1 ...................................................................................................................... 46 FIGURE 6.2 ...................................................................................................................... 47
FIGURE 6.3 ...................................................................................................................... 48 SCHEME 6.1 .................................................................................................................... 48
5
I. ABSTRACT
The long-term objective of this research is to synthesize and develop a set of
functionalized hexaphenylbenzenes capable of the controlled release of volatile fragrant
molecules, otherwise known as “pro-fragrances”. The focus of current work is on the
synthesis of original appropriately substituted 4,4’-diphenylacetylenes (tolanes). These
tolanes may be capable of scent release and can be cyclized with catalytic amounts of
cobalt octacarbonyl to form hexaphenylbenzene molecules. Efforts have focused on
optimizing the conditions and yields for the production of two tolane molecules
substituted in the 4,4’ positions with phenethyl ester groups. Upon hydrolysis, these ester
groups will release the rose-scented 2-phenylethanol molecule. Synthesis of one tolane
was accomplished through multiple steps culminating in the sequential modification of
the Sonogashira coupling reaction. The required conditions (temperature, pH, time.) for
the controlled hydrolysis of the tolane molecules were investigated via preliminary
GC/headspace analysis and are strongly dependent on the stability of the tolane molecule.
6
II. ACKNOWLEDGEMENTS
I would like to acknowledge the A.R. Smith Department of Chemistry at Appalachian
State University and its department chair Dr. Claudia Cartaya-Marin for providing me the
education and resources to be able to complete this body of work. I would also like to
thank Dr. Michael Ramey for his continued support and mentoring of this project for the
last three years of my undergraduate career. I would also like to thank Mr. Jason Selong
for his influence on me as a scientific writer, and for his support on this project. I would
also like to thank Mr. Farrar and Dr. Taubman for providing me with the information I
needed to gain a working knowledge of the headspace apparatus. Finally, I would like to
thank my family for being so incredibly supportive of me during my undergraduate
career, as well as my best friend and boyfriend Brian Clee, for without his encouragement
and loving support, this document would not exist today.
7
III. INTRODUCTION
In a world overcome with stimuli, one of the most influential stimuli seems to fly
under the radar – right under one’s nose, as they say. The smell of fresh laundry or
perfume is all due to the technology of organic synthesis. Since the 19th century, when it
was found that organic synthesis could be utilized to develop synthetic scent that
mimicked those of natural essential oils, the fragrance industry has relied on the
technology of the organic chemistry field to drive the industry.1
Fragrances: A short history
Fragrant molecules, by definition, are organic molecules that are sufficiently
volatile enough to be transported to the upper part of the nose and detected by olfactory
receptors via chemotaxis.2 Chemical compounds that are this volatile typically have a
small molecular weight, usually less than 300 amu, and are exemplified by ester, alcohol,
aldehyde, ketone, or amine functional groups, though this list is in no way exhaustive.2
There are two sources of fragrant molecules, natural sources and synthetic
sources. Natural sources of fragrant molecules are derived from plants in the form of
essential oils. There are three main ways in which these essential oils can be extracted.
The first way is through expression, when essential oils are “pressed” by inducing
physical pressure on the oil’s source.1 Citrus oils are an example of oils produced by
pressing.1 Another common form of oil isolation is through dry and steam distillation.1
Dry distillation involves high temperatures and direct flame to extract high boiling point
oils from their sources. Pine oils, for example, are derived this way. Finally, the most
common form of extraction is steam distillation and hydrodiffusion, where steam or
8
water is added to the raw materials so that the water is codistilled with the oil. Once the
oil and water mixture has been distilled, the water is then removed. Many floral oils, such
as rose oil are isolated in this manner.1
Due to the volatile nature of fragrance, large quantities of the plant from which
the scent derived from had to be grown and intensively processed. Rose oil, for example,
requires approximately 60,000 roses for the extraction of one ounce.1 Thus, until the 19th
century, fragrances were reserved only for the wealthy, as they were the only ones who
were able to afford such a costly product.1,2 If the perfume industry still relied solely on
essential oils in this manner, it would not be able to function based on the cost alone. The
discovery of synthetic fragrant molecules in the 19th century, along with Coco Chanel’s
idea of bringing high fashion to the “every woman”, helped to kick start the transition
from natural fragrances to synthetic fragrances. Unlike many natural fragrances, synthetic
molecules could be blended with other synthetic fragrances molecules to create new
fragrances, which Coco Chanel premiered with her fragrance “Chanel No.5”. The
popularity of this new fragrance revitalized the industry.1
As organic synthetic knowledge advanced, synthetic fragrance derivatives that
imitated their naturally derived counterparts and were easier and less expensive to make.
For example, the extensive process to recover rose oil could now be replaced with a
styrene monomer/propylene oxide (SMPO) process, whose efficient and low cost process
produces massive amounts of 2-phenylethanol, a rose oil analog.1, 3 Thus, fragrance
previously reserved only for the elite could now be used as an essential blending
molecule for a plethora of other fragrances.1 Fragrances were also synthesized in such a
way to maintain their integrity in more acidic and basic environments, opening the door
9
for a much wider range of scent applications. Previously unscented products, such, as
soaps, bleaches and detergents, were now fragrant and thus more marketable. Ironically,
the success of these products has led to a dye and perfume free product movement more
recently.
Pro fragrances
The economic production of organic molecules was no longer a problem, but the
length of scent release within fragranced products continued to be a tricky. Scent release
was short and uncontrolled, due to the organic compound’s volatility. Scientists searched
for a way to either lengthen the release of scent, or trigger the scent release at the desired
time. The idea of pro fragrances began in 1956 when Ashburn and Teague patented a way
to create stable aromatics and flavorings in tobacco products.4 They found by adding
small esters, compounds would remain stable and non-fragrant until burning, when the
ester bond would break and aromatic carboxylic acids would be released.4a For the next
50 years, research on the controlled release of bioactive molecules was conducted.5
Currently, there are two identified allowing scent release to be controlled and
triggered at an appropriate time.3 The first mechanism is through physical
microencapsulation of the fragrance of interest. These capsules are made of various
polymers, either to exist in more hydrophobic or hydrophilic environments, and allow for
the congregation of volatile molecules in the center of the capsule without covalent
bonding to the capsule itself.3 However, this type of pro fragrance will not be discussed
further in this body of work.
The other category of pro fragrances is similar to an approach used in drug
10
delivery systems in concept.3 This approach utilizes much larger precursors molecules
covalently bonded to volatile molecules, and is the focus of this investigation.3
Figure 3.1. General mechanism of pro fragrance
Here a volatile organic molecule is covalently bonded to the much larger substrate
molecule, until some sort of stimulus encourages bond cleavage, which splits the
fragrance molecule from its substrate (Figure 3.1). Ideally, these large precursors must be
relatively stable, but also able to decompose and release the volatile organics under mild
conditions.3 It is also desirable for a pro fragrant molecule to be able to release more than
one volatile per precursor, as to enhance the economic value of the pro fragrance itself.3
Ester bonds are easily cleavable and release alcohols and carboxylic acids.3 Cleavage of
these bonds can happen under various conditions including temperature change, pH
change, and light exposure.3 The most common form of bond cleavage found in many
products is hydrolysis in pH adjusted aqueous conditions to promote bond cleavage.3
This decomposition system is found in many products containing fragrance, including
fabric softeners, laundry detergents, soaps and shampoos.3
Hexaphenylbenzenes
For the last few years, the Ramey research group has been working on the
synthesis of various functionalized hexaphenylbenzenes6 (HPB), as seen in Equation 3.1.
Pro fragrance Substrate Volatile
Bond Cleavage
+
11
R Co Cat.
dioxane, heat
R
R
R
R
R RR
Equation 3.1. The Co catalyzed synthesis of functionalized hexaphenylbenzenes6
By starting with a di-functionalized tolane, the hexaphenylbenzene compound can be
synthesized through a cobalt catalyzed cyclization reaction capable of having 6 different
substituent groups to be attached to it, and these groups can drastically affect the physical
properties of the HPB and its subsequent reactions.6 Due to this molecule’s unique ability
to support six different substituent groups, the question can be asked – can
hexaphenylbenzenes act as a highly efficient delivery system for scent release?
Focus of the Project
The focus of this project is to synthesize a precursor-esterified tolane with a
methylene spacer that can be cyclized in the future to produce an ester functionalized
hexaphenylbenzene pro fragrant molecule. Because many fragrance molecules are
alcohols, it is believed that if the six functional arms of the hexaphenylbenzene are
substituted with ester groups, these six alcohol molecules can be released upon
hydrolysis, leaving the hexaphenylbenzene with carboxylic acid substituted arms, as seen
in Figure 3.2.
12
Figure 3.2. General ester hydrolysis reaction
The conjugation of the hexaphenyl group itself, and large size of the molecule will
provide ample stability for the molecule until put under hydrolysis conditions. The
hexasubstituted esters would give the pro-fragrance more “bang for its buck” with the
ability to hydrolyze six ester groups per molecule as opposed to just one. Additionally,
the resulting carboxylic acid product can act as an antimicrobial, as carboxylic acids are
commonly used for this purpose.3
The rate of hydrolysis for these esters is dependent upon three major factors: the
stability of the ester bond in the precursor structure, temperature, and the pH of
hydrolysis conditions.3 Primary alcohols, as part of the ester structure, proliferate the rate
of hydrolysis better than secondary or tertiary alcohols. Neighboring nucleophillic groups
can intramolecularly attack the ester carbonyl thus releasing the alcohol and increasing
the rate of hydrolysis.3 Knowing this, the alcohol of interest to be attached to each arm of
the hexaphenylbenzene will be the primary alcohol 2-phenylethanol (Figure 3.3).
(O
O )6
Figure 3.3. 2-phenylethanol functionalized Hexaphenylbenzene
R O
O
R'hydrolysis
R OH
O
+ OH R'
13
With the phenyl rings out of plane, along with the 2-phenylethanol being a primary
alcohol, the ester bond should be able to cleave under relatively mild hydrolysis
conditions. The exact conditions of hydrolysis will begin to be determined via GC
headspace analysis.
Sonogashira Coupling Reaction
Prior to cyclization to the hexpahenylbenzene, a synthetic route to the tolane
precursor must be found. A pro fragrance molecule in its own right, this difunctionalized
diphenyl acetylene would have similar properties to the hexaphenylbenzene. Synthesis of
the tolane precursor will be completed via the Sonogashira coupling reaction. This
palladium-catalyzed reaction is useful in synthesizing carbon-carbon bonds. The
mechanism of the Sonogashira coupling reaction, along with other coupling reactions,
like the Suzuki and Stille coupling reactions, involves the use of a three step catalytic
cycle7 (Scheme 3.1).
14
Pd(0)
L
L
Pd(II)
L
L
XRPdL
L
R
R'CuCu X
R X
transmetallation
oxidativeaddition
R'
R R'
reductiveelimination
Scheme 3.1. General Pd(0) catalytic cycle8
Once the palladium(II) catalyst is activated to Pd(0) through reduction with copper and
terminal alkyne, the Pd(0) reacts with an aryl halide in an oxidative addition to yield a
Pd(II) intermediate. This intermediate then undergoes a transmetallation step with a
copper acetylide. A terminal alkyne is reacted with a catalytic amount of CuI in a
separate cycle. The transmetallation couples the acetylide to the palladium catalyst and
expels a copper halide. Finally, in a reductive elimination reaction, the tolane is
produced, and the palladium catalyst is regenerated.8
Generally, Scheme 3.2 depicts an aryl iodide that is connected to a terminal
acetylene,9 which is then used in a second sonogashira reaction with the acetylene again
to make a tolane.
15
Scheme 3.2. Sequential Sonogashira Coupling reaction9
Completion of two coupling reactions as shown above, with deprotected acetylene as an
intermediate, is called a sequential Sonogashira coupling reaction. Positive aspects of
completing a Sonogashira coupling reaction in this manner includes insuring that the
proper acetylene intermediate is being synthesized, thus assuring that the final tolane will
be produced upon the second coupling. However, this sequential method can be time
consuming, and isolation of the terminal acetylene after the first coupling can cause some
product loss, which would lower the yield of the final tolane.
Besides the sequential method, the reaction may also occur all at once, called the
“one-pot” method, as seen in equation 3.2.10
Equation 3.2. “One-pot” Sonogashira Coupling reaction
The above method monoprotects and deprotects the acetylene in situ through the use of
X RPdo, CuI
amidine basetoluene, H2O0.5eq. Si(CH3)3
RR
X = Br, IR = ester, nitrile, OR, NR3, alkyl
X = Br, I R1= ester, nitrile, OR, NR3, alkyl
16
amidine base and a small stoichiometric amount of water. This method is much faster
than the sequential method. Though, if the stoichiometric amounts are incorrect, there is a
chance that the reaction will fail, meaning more precious synthetic material is ruined.
However, both methods can be investigated to synthesize any disubstituted tolane of
interest.
Previous Work
A diester tolane whereby the ester functional group was directly attached to the
benzene ring was successfully synthesized using a one-pot Sonogashira coupling reaction
(Figure 3.4). However, it was found via preliminary headspace analysis that the tolane
required 1mL of water, acetone and concentrated HCl to release the volatile 2-
phenylethanol11 (Figure 3.5).
Figure 3.4 - Previous tolane precursor without a CH2 spacer.
It is believed that the conjugation of the ester caused the tolane to be too stable for the
desired mild hydrolytic conditions. It was determined that an ester precursor with a
methylene (-CH2-) spacer between the benzene ring and carbonyl group should lessen the
stability and allow for hydrolysis under more mild conditions.
I
O
O CuI
DBUtoluene, H2O
Si(CH3)3
O
O
O
O
PdCl2(PPh3)2
Compound A
Target Molecule I30 %
mp. 138-140oC
0.5 eq H
17
Figure 3.5 - Previous GC headspace analysis results.12
Synthetic Route
The proposed route for synthesizing the spacer tolane will involve the sequential
Sonogashira coupling reaction to ensure completion of the reaction and for proof of
concept, as seen in Scheme 3.3.
18
1.
2.
3.
4.
Scheme 3.3 – Synthetic route to methylene spacer (-CH2-) disubstituted ester
functionalized tolane
The starting iodinated carboxylic acid can be esterified via nucleophillic acyl substitution
of an acid chloride in-situ with the subsequent addition of 2-phenylethanol to yield the
aryl ester halide. The synthesized aryl ester halide will then be a part of the successive
Sonogashira coupling reactions.
19
Overall, the project will focus on the stepwise synthesis of a methylene spacer
tolane, which will then be tested for its ability to release 2-phenylethanol via mild
hydrolysis conditions via a preliminary headspace analysis method.
20
IV. SYNTHESIS
Carboxylic Acid Synthesis
In order to synthesize a di-substituted diester tolane precursor, a halogenated ester
must first be produced. It was found that one of the most efficient ways to produce this
ester was to esterify an iodinated carboxylic acid. In order to create a pro-fragrant
molecule that could easily degrade under neutral conditions, an ester derived from
phenyl-acetic acid was the target molecule. This molecule possesses a CH2 spacer
between the aromatic ring and carbonyl group, making the ester less stable; theoretically
making the ester more able to hydrolyze. Iodine was chosen as the halogen due to its
excellent behavior in palladium catalyzed reactions. The iodination occurs in one step,
involving the basic addition of acid and iodine. Equation 4.1 outlines the iodination
procedure used to synthesize (4-iodo-phenyl)-acetic acid (1) from phenyl acetic acid, a
commercially available reagent.
Equation 4.1. Iodination to synthesize (1)13
Based on an article by Waybright13 and synthesized by Alex Cella, phenyl acetic acid and
(1) 48% yield
mp: 129° C
21
iodine were added together with glacial acetic acid, followed by a slow drop wise
addition of a 1:4 mixture of concentrated nitric and sulfuric acids. Then, the solution was
heated to 60° C for approximately 1.5 hours. The solution was then removed from heat
and allowed to stir at room temperature overnight. The mixture was then poured over ice
and vacuum filtered. At this point, a pink solid was recovered and recrystallized from
hexanes to produce (4-iodo-phenyl) – acetic acid (1) in 45% yield. Gas chromatography
and mass spectrometry (Figure 4.2) were used to help identify (1) with a retention time of
18.25 minutes and a molecular ion peak at 262 m/z.
Figure 4.1. Gas chromatogram and mass spectrum of isolated (4-iodo-phenyl)-acetic acid
60 80 100 120 140 160 180 200 220 240 2600
5000
10000
15000
20000
25000
30000
35000
40000
45000
50000
55000
60000
m/ z-->
Abundance
Scan 2064 (14.291 min): iodophenylaceticacid.D\ data.ms261.9216.9
90.0
63.0
126.8107.1 243.8164.7
4 .00 6 .00 8 .00 10 .00 12 .00 14 .00 16 .00 18 .00 20 .00 22 .00 24 .00 26 .00 28 .00
500000
1000000
1500000
2000000
2500000
3000000
3500000
4000000
4500000
5000000
5500000
6000000
6500000
T ime-->
A bundanc e
T IC: iodophenylac e tic ac id .D \ da ta .ms
22
In addition to GC/MS analysis, 1H NMR and 13C NMR analysis was conducted, and
peaks coincided with literature values.13
Ester Synthesis
(4-iodo-phenyl) – acetic acid (1) was then dissolved in a 2:1 molar excess of
thionyl chloride under a dry nitrogen atmosphere in order to convert the carboxylic acid
into a more reactive acid chloride. Once the mixture stirred at room temperature for two
hours, excess thionyl chloride was removed from the solution via reduced pressure and
temperature by iced vacuum pump. This was done to ensure no excess thionyl chloride
remained to interfere with the next step of the reaction. No further purification or
characterization was performed on the thionyl chloride intermediate. A 1:1 molar ratio of
chilled 2-phenyl-ethanol was then added drop wise to the reaction, as shown by Equation
4.2. The 2-phenyl-ethanol was cooled, and added to the reaction. The reaction was
allowed to stir at room temperature under atmospheric conditions overnight. The solution
was then
extracted with methylene chloride, washed twice with
concentrated sodium
hydroxide, and dried over MgSO4.
Equation 4.2. Esterification of compound (1) to synthesize compound (2)14
This approach to synthesizing (2) was much more successful, despite its modest yield
(48%), than our previous attempts at a Fischer esterification which did not seem to
(1) (2) 48%
23
produce any product at all. The acidic conditions required for a Fischer Esterification
may have degraded the aromatic iodinated compound. Initial GC/MS results showed
unreacted 2-phenylethanol in the product. Removal of the alcohol was accomplished by
flash chromatography with methylene chloride. The product’s Rf value was much higher
than the alcohol. Gas chromatograph/mass spectrometry was used to characterize
compound (2), with a retention time of 21.2 minutes and a molecular ion peak of 366
m/z. Post column chromatography yielded a relatively pure yellow viscous liquid, whose
identity was indicated via gas chromatography and mass spectrometry (Figure 4.2).
Figure 4.2. Gas chromatogram and mass spectroscopy at 21.42 minutes of isolated (4-
iodophenyl) – acetic acid phenethyl ester
4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00 24.00 26.00 28.00
2000000
4000000
6000000
8000000
1e+07
1.2e+07
1.4e+07
Time-->
Abundance
TIC: iodospacerester.D\data.ms
6 0 8 0 1 0 0 1 2 0 1 4 0 1 6 0 1 8 0 2 0 0 2 2 0 2 4 0 2 6 0 2 8 0 3 0 0 3 2 0 3 4 0 3 6 00
2 0 0 0 0 0
4 0 0 0 0 0
6 0 0 0 0 0
8 0 0 0 0 0
1 0 0 0 0 0 0
1 2 0 0 0 0 0
1 4 0 0 0 0 0
1 6 0 0 0 0 0
1 8 0 0 0 0 0
2 0 0 0 0 0 0
2 2 0 0 0 0 0
2 4 0 0 0 0 0
2 6 0 0 0 0 0
2 8 0 0 0 0 0
3 0 0 0 0 0 0
3 2 0 0 0 0 0
3 4 0 0 0 0 0
3 6 0 0 0 0 0
m/ z-->
A b u n d a n c e
S c a n 3 4 3 8 (2 1 .4 2 0 min ): io d o sp a c e re ste r.D \ d a ta .ms1 0 4 .0
2 1 6 .9
2 6 1 .9
7 7 .05 1 .0 1 6 7 .11 2 6 .9 3 6 6 .01 9 1 .0 2 9 2 .9 3 3 7 .0
24
Figure 4.3. 1H NMR and 13C NMR spectra of compound (2) with atom assignments
1H NMR analysis and 13C NMR analysis confirmed the identity of (2), as evidenced in
Figure 4.3. The number of peaks from proton NMR matches the number of unique
hydrogens predicted on compound (2). The chemical shift (4.3 ppm) and integration (2)
of peak b indicates two hydrogens that have high shielding, indicating their location next
to a heteroatom such as an ether oxygen. Peak a also has a higher ppm (3.5, singlet) with
shielding, indicating its location next to an electron withdrawing group, such as a
a d
c
b
aromatic
25
carbonyl group or benzene ring. Peak c suggests a higher chemical shift (2.8ppm), but not
as dramatic as the other two peaks, which corresponds with the desired compound (2).
Additionally, signals in the aromatic region correspond with both the presence of mono-
substituted phenyl rings and a disubstituted phenyl ring.
Carbon spectral analysis was also indicative of a confirmed identity of compound
(2). Literature values of compound (1)13 show that there are only two other carbon peaks
besides those associated with the aromatic region; a peak in the carbonyl NMR region,
and a peak just below the aromatic region. Figure 2.5 illustrates that the additional peak c
(65 ppm) in the ether region and peak d (38 ppm), in addition to the peaks previously
listed in the literature about compound (1), confirm the addition of 2-phenylethanol to
compound (1) in an ester linkage. Overall, instrumental analysis confirmed the identity of
compound (2).
Terminal Alkyne Synthesis
As earlier discussed, it was determined for educational purposes to complete the
tolane synthesis via a sequential Sonogashira coupling reaction.7, 9 Figure 2.6 displays the
Sonogashira coupling reaction used to synthesize the first intermediate (4-ethynyl-
phenyl)-acetic acid phenethyl ester (3).
O
OI
1. 1.05 eq. Si(CH3)3Pd0, CuI, NEt3
2. TBAF, THF 1 h O
O
23
Equation 4.3. Sonogashira coupling reaction to synthesize (4-ethynyl-phenyl)-acetic acid phenethyl ester (3)
53%
26
Under a nitrogen atmosphere, the previously synthesized compound (2) was added to N2
sparged triethylamine. After the ester dissolved, The Pd and Cu catalysts were added at 3
mole percent to the reaction flask. After addition of the catalysts, trimethylsilylacetylene
(TMS acetylene) was added drop wise in slight molar excess in order to account for the
small amount consumed during the reduction stage of the Pd (II) catalyst. As the TMS
acetylene was added, small white crystals precipitated, thought to be triethylamine salts,
indicating that the reaction was working. After addition of the TMS acetylene, the
reaction was stirred under a low heat for three hours. After three hours the heat was
removed and the solution allowed to stir for 72 hours. After this time, the solution was
filtered via vacuum filtration and the solvent removed via rotary evaporation. After
removal of the solvent, the crude product was dissolved in methylene chloride and
washed with 6M HCl, water and a saturated brine solution, then dried over MgSO4. After
drying, the catalysts were removed via flash chromatography using methylene chloride
and the solvent removed via rotary evaporation. TLC analysis was utilized to examine the
crude product in comparison with its reagents. TLC found that the TMS-intermediate had
an Rf value lower than that of the original ester, indicating that a larger group had been
attached during the reaction.
To reduce the TMS protecting group to a terminal hydrogen, The TMS-acetylene
intermediate was dissolved in tetrahydrofuran (THF) and reacted with 3 percent molar
excess of tetrabutylammonium fluoride (TBAF). This reaction was allowed to stir at
room temperature for 1 hour, after which the THF was removed via rotary evaporation.
After the solvent was removed, the crude product was extracted with methylene chloride,
and washed with 6M HCl, water and brine solutions. Flash chromatography with
27
methylene chloride was attempted to further purify the product, but isolation of the
product was not achieved, and TLC analysis indicated that the product had severe
contamination. Because of this contamination, column chromatography using methylene
chloride resulted in less than 10% yield. It is uncertain whether future reactions of this
nature will need such a high level of purification, so proper utilization of flash
chromatography may only be needed. Gas chromatography and mass spectrometry data
displayed the product after column chromatography with an Rt of 19.49 minutes and a
molecular ion peak of 264 m/z (Figure 4.4).
28
Figure 4.4. Gas chromatography and mass spectrometry of compound (3) at 19.49
minutes.
4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00 24.00 26.00 28.000
500000
1000000
1500000
2000000
2500000
3000000
3500000
4000000
Time-->
Abundance
TIC: tbafcolumnedhacetylester.D\data.ms
6 0 8 0 1 0 0 1 2 0 1 4 0 1 6 0 1 8 0 2 0 0 2 2 0 2 4 0 2 6 0 2 8 00
5 0 0 0
1 0 0 0 0
1 5 0 0 0
2 0 0 0 0
2 5 0 0 0
3 0 0 0 0
3 5 0 0 0
4 0 0 0 0
4 5 0 0 0
m / z -->
A b u n d a n c e
S c a n 3 0 6 7 (1 9 .4 9 5 m in ): tb a fc o lu m n e d h a c e ty le s te r.D \ d a ta .m s1 0 4 .0
2 0 5 .11 6 0 .0
2 6 4 .17 7 .0
5 1 .01 2 7 .8 2 8 1 .01 7 7 .9
29
1H NMR and 13C NMR analysis indicated that (3) was in fact synthesized in relatively
pure form, as indicated in Figure 4.5.
Figure 4.5. 1H NMR and 13C NMR spectra of compound (3) with atom assignments
f
TMS standard
TMS standard
30
Proton NMR, even at a glance indicates that a new compound was synthesized. Unlike
proton NMR from Figure 6, there is a new proton singlet (3.1 ppm) that appeared just
above peak c (2.8 ppm) and below peak a (3.5 ppm) in the alkyne hydrogen region of the
NMR. Further, peaks e (85 ppm) and f (121 ppm) on the 13C NMR shifted downfield
denotes an alkyne substituted in the iodine’s place from compound (2).
Diester Tolane Synthesis
To synthesize the diester tolane, as depicted in Figure 4.4, compound (3) was reacted
with compound (2) in a final Sonogashira coupling reaction. This last coupling reaction
differs from the first coupling reaction in that the two reactants are reacted in a 1:1 ratio,
not in a 1.05 molar excess. The reaction proceeded by dissolving compound (3) in
sparged triethylamine and adding it via syringe to a side arm flask full of N2 sparged
triethylamine put under a nitrogen atmosphere. After, 3 mole percent of CuI and
PdCl2P(Ph3)2 was added to the side arm flask, compound (2) was added drop wise via
syringe into the reaction mixture to yield small white crystals that, as mentioned earlier,
indicate progress of the reaction. The mixture was heated and stirred for three hours, the
heat was then turned off and the mixture was allowed to stir for 72 hours. After this time,
the solvent was removed via rotary evaporation, extracted with methylene chloride, and
washed with 6M HCl, water, and brine solutions. To remove catalyst residue, flash
chromatography was attempted and the crude mixture was then analyzed via TLC.
31
Equation 4.4. Sonogashira coupling to produce the desired diester tolane compound (4)
TLC analysis indicated that there was an entirely new spot that had about half of the Rf
value of the original ester. This looked promising, so the crude product was analyzed via
gas chromatography and mass spectrometry. However, it is uncertain if product was
made, since the large size of compound (4) may make gas chromatography an
inappropriate method for analysis, and liquid chromatography (LC) was not readily
available. A carbon NMR was also run on the crude product (Figure 4.6). It is believed
the peaks are present in the spectrum to confirm the synthesis of compound (4).
Additional purification would be necessary along with improvements in the synthesis to
maximize yields.
(3) (4) (2), heat
32
Figure 4.6. 13C NMR of final tolane crude mixture
33
V. HEADSPACE ANALYSIS
In order to determine whether the spacer tolane molecule is capable of volatile
release, the knowledge of headspace analysis needed to be acquired. The conditions
under which the tolane hydrolyzes should be mild, and within pH and temperature ranges
that can be found in every day applications. Physiological temperature and pH make pro
fragrances useful for topical application and more rigorous conditions such as the
temperature of a clothes dryer make them more useful for “industrial” applications.
Direct injection gas chromatography is useful for molecules that are volatile and easily
converted into the gas state. Our pro fragrant molecules would be high molecular weight
species that are undergoing a reaction to release volatile components. GC/ headspace
analysis is ideal for this application as it acquires the vapor from above the “original
sample” regardless of the volatility of the original material.
Gas Chromatograph/Headspace Apparatus
Unlike gas chromatography, where the liquid form of the sample of interest is
directly injected then volatilized within the column, headspace analysis works a slightly
different way.
Figure 5.1. Headspace analysis and gas chromatography general mechanism15
34
As seen in Figure 5.1, the injector draws from the gaseous volatiles that are located above
the liquid sample after it has been exposed to heat or hydrolysis conditions. Once the gas
has been extracted from the sample vial, the sample is transferred to the gas
chromatograph where it is run through a column to determine retention time.15
Additionally, mass spectroscopy (MS) may be attached as an additional detector at the
end of the instrument. MS detection aides in identifying components in the GC without
having to run standards of know materials that could possibly be in the sample.
Surrogate Molecule
In order to conserve previous synthetic tolane materials, it was decided that
method development would utilize a surrogate molecule that hydrolyzed into the same
types of constituents. Ideally, this surrogate molecule upon hydrolysis would release the
alcohol of interest, 2-phenylethanol. It was also desired that this surrogate molecule be
commercially available, so that extra synthesis was not needed, and that large quantities
could be acquired for method development. An initial SciFinder scholar structure search
produced 2-phenylethyl acetate as a suitable surrogate, as shown in Equation 5.2.
Equation 5.1. 2-Phenylethyl acetate hydrolysis
This molecule is commercially available and hydrolyzes into the alcohol of interest and
+ Mild Hydrolysis
2-phenylethyl acetate 2-phenylethanol Acetic acid
35
an acetic acid. Preliminary method development was conducted on this proxy, with the
anticipation that hydrolysis conditions for the final tolane would be similarly mild.
Preliminary Method Development
With no prior experience with headspace analysis, development of a workable
method included a steep learning curve. As such, a rough method was devised based on
another student’s previous work that involved analyzing hop essential oils, along with a
working knowledge of the conditions under which a pro fragrant sample would ideally
volatilize.15 The column through which the headspace would run through was 15 meters
long (more details on the column can be found in the Experimental section). Injection
type would be splitless since the sample analyzed would most likely be very dilute. The
static headspace sampling technique was to be used.15
Because the ideal conditions which the alcohol was desired to volatilize under, it
was undesirable to have the temperature program go above 1000C, as to avoid boiling and
over pressurization of the sample vial. Practical applications of this molecule may include
its use in a dryer sheet fragrance and typical dryer temperatures approach temperatures
around 55-75 0C.16 As such, the following temperature program was devised (Table 3.1).
Table 5.1. Temperature Program
Stage Rate (°C/min) Temp (°C) Initial injection ---- 55 Inlet ---- 65 Gas chromatograph ---- 75
Heating of the headspace vial was held constant at 55 degrees, but the inlet and gas
36
chromatograph temperatures were heated ten degrees higher in order to promote volatile
movement and separation from injection to inlet to gas chromatograph since pressure for
the gas chromatograph was held at 15 psi, and the other end of the loop was not under
vacuum to help push the volatiles through the loop. Once volatiles entered the gas
chromatograph, they were subject to the Ramey research method. (See Experimental
Section for details of this GC program)
Results
To know the retention time of the 2-phenylethanol that would hopefully release from the
surrogate molecule, a 1-mL sample of 98% commercially available 2-phenylethanol was
run through the preliminary headspace method.
Figure 5.2. Gas chromatograph of 98% pure, commercially obtained, 2-phenylethanol
(RT: 4.753 minutes)
4 .0 0 5 .0 0 6 .0 0 7 .0 0 8 .0 0 9 .0 0 1 0 .0 0 1 1 .0 0 1 2 .0 0 1 3 .0 00
5 0 0 0 0 0
1 0 0 0 0 0 0
1 5 0 0 0 0 0
2 0 0 0 0 0 0
2 5 0 0 0 0 0
3 0 0 0 0 0 0
3 5 0 0 0 0 0
4 0 0 0 0 0 0
4 5 0 0 0 0 0
5 0 0 0 0 0 0
5 5 0 0 0 0 0
6 0 0 0 0 0 0
T im e -->
A b u n d a n c e
T IC : 2 p h e n y e th a n o lh y d ro .D \ d a ta .m s
3 .2 2 0 3 .2 3 8 3 .2 7 4 3 .3 2 4 3 .3 4 9 3 .4 0 7 3 .4 5 5 3 .4 9 3 3 .5 2 1 3 .5 4 5 3 .5 6 7 3 .6 0 3 3 .6 2 6 3 .6 6 5 3 .7 7 5 3 .8 5 7 3 .9 2 1 4 .0 0 6 4 .0 5 9 4 .1 1 0 4 .1 4 1 4 .1 9 9 4 .2 1 6 4 .2 3 5 4 .2 8 9 4 .3 1 2 4 .3 7 9 4 .4 3 1 4 .5 4 6 4 .5 8 6 4 .6 0 9
4 .7 3 3
4 .9 4 9 4 .9 8 8 5 .0 7 4 5 .1 0 2 5 .1 5 5 5 .1 9 4 5 .2 9 4 5 .3 8 1
5 .4 9 4
5 .5 5 0 5 .6 2 8 5 .6 6 5 5 .7 0 3 5 .7 3 3 5 .7 8 0 5 .8 0 4 5 .8 5 1 5 .9 1 4 5 .9 4 3 5 .9 7 4 6 .0 3 2 6 .0 5 6 6 .1 0 4 6 .1 6 1 6 .1 8 1 6 .1 9 9 6 .2 6 6 6 .2 9 6 6 .3 2 4 6 .3 7 8 6 .4 0 1 6 .4 6 4 6 .5 0 6 6 .5 5 3 6 .6 5 5 6 .7 1 3 6 .7 5 4 6 .8 0 9 6 .9 0 1 6 .9 4 5 7 .0 0 1 7 .0 5 2 7 .1 0 7 7 .1 7 0 7 .2 3 4 7 .2 7 6 7 .2 9 8 7 .3 7 9 7 .4 6 3 7 .4 9 6 7 .5 4 5 7 .5 7 6 7 .6 6 4 7 .7 1 0 7 .7 4 0 7 .7 6 5 7 .8 2 1 7 .9 1 5 7 .9 6 1 7 .9 9 3 8 .0 4 9 8 .2 5 3 8 .3 7 5 8 .4 8 8 8 .5 8 2 8 .6 2 8 8 .6 5 5 8 .7 1 7 8 .9 6 7 9 .0 5 1 9 .3 4 0 9 .5 7 9 9 .9 0 51 0 .0 7 91 0 .1 4 91 0 .1 9 11 0 .2 1 41 0 .2 4 61 0 .3 1 81 0 .5 7 51 0 .6 8 91 1 .0 9 71 1 .6 7 01 2 .5 0 61 2 .5 3 31 2 .6 4 41 3 .3 8 31 3 .4 0 61 3 .4 9 71 3 .5 9 8
37
As seen by Figure 5.2, because this sample was not completely pure, there was some
contamination that showed up in the gas chromatograph, but the largest peak at 4.753
minutes appeared to be 2-phenylethanol. The mass spectrum for the 4.753 peak was
analyzed to confirm identity of sample.
Figure 5.3. Mass spectrum of GC peak at 4.753 minutes
As seen in Figure 5.3, mass spectrometry showed that there was an M+ peak of 122 and
base peak of 91.1, which runs in line with the expected mass spectrum of 2-
phenylethanol. This confirmed that 2-phenylethanol has a retention time of about 4.753
minutes in the developed headspace method. Any 2-phenylethanol in a headspace sample
should have this approximate retention time and exact MS spectrum.
Once the identity and retention time of 2-phenylethanol was confirmed, 1 mL of
2-phenylethyl acetate sourced from the chemistry department stockroom w
4 5 5 0 5 5 6 0 6 5 7 0 7 5 8 0 8 5 9 0 9 5 1 0 0 1 0 5 1 1 0 1 1 5 1 2 0 1 2 5 1 3 00
1 0 0 0 0 0
2 0 0 0 0 0
3 0 0 0 0 0
4 0 0 0 0 0
5 0 0 0 0 0
6 0 0 0 0 0
7 0 0 0 0 0
8 0 0 0 0 0
9 0 0 0 0 0
1 0 0 0 0 0 0
1 1 0 0 0 0 0
1 2 0 0 0 0 0
1 3 0 0 0 0 0
1 4 0 0 0 0 0
1 5 0 0 0 0 0
1 6 0 0 0 0 0
m / z - - >
A b u n d a n c e
S c a n 2 8 3 ( 4 . 7 0 0 m i n ) : 2 p h e n y e t h a n o l h y d r o . D \ d a t a . m s9 1 . 1
1 2 2 . 1
6 5 . 0
7 7 . 05 1 . 01 0 3 . 0
8 4 . 0
38
Figure 5.4. Gas Chromatograph of stockroom 2-phenylethyl acetate. No additional
reagents added.
As seen from Figure 5.4, there were two major peaks that showed up via GC analysis.
Mass spectral analysis of the retention time at 4.652 revealed that this was 2-
phenylethanol, as indicated in Figure 5.5.
4.00 5.00 6.00 7.00 8.00 9.00 10.00 11.00 12.00 13.000
1000000
2000000
3000000
4000000
5000000
6000000
7000000
8000000
Time-->
Abundance
TIC: phenethylacetatehydrostraight.D\ data.ms
3.223 3.759 4.135
4.652
4.773 4.839 4.872 4.967 5.012 5.034 5.139 5.196 5.267 5.314 5.347 5.385 5.412 5.443 5.481 5.832 6.062 6.392
6.618
6.785 6.806 6.827 6.847 6.905 6.922 6.961 6.995 7.019 7.059 7.229 7.273 7.307 7.335 7.393 7.426 7.485 7.524 7.586 7.615 7.640 7.677 7.802 7.949 8.041 8.305 8.355 8.463 8.961 9.335 9.398 9.453 9.856 9.94910.707 13.58913.606
39
Figure 5.5. Mass spectrum of peak at RT 4.652 minutes in stockroom 2-phenethyl acetate sample
Figure 5.6. Mass spectrum of peak at RT 6.618 minutes in stockroom 2-phenethyl acetate sample.
45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 1300
20000
40000
60000
80000
100000
120000
140000
160000
180000
200000
220000
m/ z-->
Abundance
Scan 273 (4.643 min): phenethylacetatehydrostraight.D\ data.ms91.0
122.0
65.0
51.0 77.0 103.0
50 60 70 80 90 100 110 120 130 140 150 160 1700
500000
1000000
1500000
2000000
2500000
3000000
3500000
m/z-->
Abundance
Scan 613 (6.589 min): phenethylacetatehydrostraight.D\data.ms104.1
91.1
65.1 78.151.1121.1 131.0 163.0145.0
40
Mass spectra analysis was also conducted on the peak at retention time 6.618 minutes.
Mass spectral analysis indicated that for the peak at 6.618 minutes, there was an M+ of
163, with a base peak of 104.1 (Figure 5.6). These values match ions for the surrogate
molecule 2-phenylethyl acetate, which is a volatile ester, unlike our proposed tolane
esters, which would not be volatile. From this analysis, it was thus determined that both
2-phenylethanol (RT=4.652) and the surrogate ester (RT=6.618) were present in the
headspace sample. Hydrolysis of the stockroom ester sample had occurred during
storage or was occurring quite rapidly at the vial temperature of 55 0C.
To try to promote hydrolysis, another sample was prepared and analyzed with 1
mL of DI water and 1 mL of ester.
Figure 5.7. GC results of mixture of 1 ml stockroom 2-phenethyl acetate and 1 ml DI
water
4.00 5.00 6.00 7.00 8.00 9.00 10.00 11.00 12.00 13.000
1000000
2000000
3000000
4000000
5000000
6000000
7000000
8000000
Time-->
Abundance
TIC: phenethylacetatehydrohydro.D\ data.ms
3.216 3.753 4.138 4.650 4.792 4.838 4.926 4.969 5.029 5.098 5.117 5.184 5.310 5.366 5.478 5.544 5.857 6.389
6.620
6.814 6.837 6.887 6.927 6.965 6.994 7.014 7.047 7.171 7.226 7.346 7.391 7.452 7.487 7.517 7.575 7.610 7.660 7.700 7.743 7.801 7.948 8.043 8.319 8.353 8.467 8.516 8.961 9.306 9.393 9.450 9.681 9.852 9.94710.70311.400 13.594
41
Gas chromatograph indicated from Figure 5.7 that both the alcohol and ester were present
in the headspace sample. In hopes to promote hydrolysis further, various concentrations
of hydrochloric acid (HCl) were added to different samples with a 50/50 mixture of 2-
phenylethyl acetate and water.
Figure 5.8. GC results of mixture of 1 ml ester, 1 ml DI water, and 2 drops of conc. HCl
Results from adding two drops of HCl seemed to improve results slightly, as seen in
Figure 5.8, however the concentration of 2-phenylethanol was still significantly below
1000000 in abundance. So to another sample, 1 mL of 1M HCl was added to a 50/50
mixture of 2-phenylethyl acetate and DI water.
2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 11.00 12.00 13.000
100000
200000
300000
400000
500000
600000
700000
800000
900000
1000000
1100000
1200000
Time-->
Abundance
TIC: with 2 drops conc acid.D\ data.ms
1.124 1.171 1.218 1.410 1.495 1.530 1.573 2.831
3.029 3.243 3.780 4.122 4.158
4.669
4.792 4.847 4.910 4.954 4.988 5.031 5.060 5.094 5.147 5.178 5.221 5.326 5.456 5.493 5.872 6.402
6.631
6.821 6.863 6.898 6.959 6.981 7.023 7.053 7.206 7.240 7.277 7.324 7.418 7.449 7.516 7.563 7.597 7.721 7.738 7.771 7.807 7.917 7.959 7.993 8.050 8.139 8.220 8.241 8.319 8.367 8.407 8.470 8.520 8.641 8.733 8.790 8.973 9.213 9.338 9.393 9.463 9.575 9.690 9.793 9.864 9.95410.70910.88011.41511.74312.22212.27212.30112.81412.91613.49513.55513.60413.64413.80313.83113.90713.938
42
Figure 5.9. GC results of mixture of 1 ml ester, 1 ml DI water, and 1 ml of 1M HCl
Surprisingly, adding 1M HCl did not improve yield of 2-phenylethanol, and actually
lowered its concentration, as shown in Figure 5.9. To see if a higher concentration of acid
would improve results, 1 mL of 6M HCl was added to a final mixture of 50/50 ester and
water.
1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 11.00 12.00 13.000
100000
200000
300000
400000
500000
600000
700000
800000
900000
1000000
1100000
Time-->
Abundance
TIC: 1 mL 1 M acid.D\data.ms
0.554 0.580 0.629 0.646 0.747 0.776 0.884 0.900 0.925 0.967 1.083
2.810 3.227 3.762 4.146
4.656
4.837 4.865 4.909 4.942 4.967 5.016 5.068 5.112 5.171 5.315 5.484 5.864 6.395 6.484
6.624
6.802 6.851 6.916 6.963 6.996 7.032 7.071 7.126 7.150 7.169 7.200 7.227 7.288 7.393 7.474 7.526 7.550 7.598 7.709 7.760 7.802 7.848 7.928 7.977 8.043 8.156 8.215 8.234 8.264 8.304 8.339 8.354 8.462 8.680 8.733 8.962 9.028 9.118 9.172 9.392 9.454 9.682 9.858 9.95110.696 13.601
43
Figure 5.10. GC results of mixture of 1 mL ester, 1 mL DI water, and 1 mL of 6M HCl
As Figure 5.10 indicates, a slightly higher concentration of 2-phenylethanol was found
than all other mixture conditions. However, all conditions analyzed did not produce
optimal release of 2-phenylethanol. Comparison of the peak integration area of ester to
that of the integration area of the alcohol did not seem to indicate improved hydrolysis
over the neat stockroom 2-phenethyl acetate sample nor were the results very consistent.
Discussion
Overall, the objectives of this preliminary headspace analysis were to obtain a
working understanding of how headspace analysis works, and to establish a rough,
preliminary headspace analysis method to analyze the rate of 2-phenylethanol release
from a molecule similar to the spacer tolane. Both of these objectives were attained,
4.00 5.00 6.00 7.00 8.00 9.00 10.00 11.00 12.00 13.000
100000
200000
300000
400000
500000
600000
700000
800000
900000
1000000
1100000
1200000
T ime-->
Abundanc e
T IC: 6M H Cl 1 mL.D \ data.ms
3.777 4.119 4.155
4.664
4.837 4.877 4.916 4.981 5.022 5.090 5.114 5.137 5.211 5.241 5.321 5.413 5.491 5.561 5.628 5.682 5.836 5.870 5.983 6.018 6.358 6.399 6.464
6.628
6.865 6.891 6.919 7.055 7.076 7.099 7.139 7.231 7.287 7.358 7.392 7.466 7.696 7.728 7.802 7.862 7.941 7.985 8.046 8.164 8.229 8.278 8.311 8.339 8.364 8.406 8.468 8.531 8.717 8.736 8.963 9.006 9.207 9.333 9.399 9.456 9.573 9.691 9.857 9.951 10.84610.88710.91810.94610.98511.01911.08711.10511.15711.18211.23111.33011.34711.40911.42811.50011.65711.69411.827 12.72513.43913.60513.80513.908
44
however the results of this preliminary analysis were somewhat unanticipated. Though it
was not surprising that the surrogate molecule would volatilize along with the 2-
phenylethanol due to its low molecular weight, the low concentration of 2-phenylethanol
while including acid was surprising at first. One would imagine that acidifying the water
would promote hydrolysis of the ester, and to a certain extent this did happen. The
progression of release as concentration and volume of HCl was added did increase the
concentration of alcohol. However, the concentration of 2-phenylethanol was rather low.
However, further literature research did reveal that addition of a buffer system would
have been both more realistic for practical applications, and to assist in hydrolysis of the
ester bond. Also, all reaction mixtures analyzed were not entirely pure or distilled, and
due to the age of the 2-phenylethyl acetate, some decomposition of the molecule may
have occurred, and as such the 2-phenylethanol that was observed on the GC was mostly
previously decomposed with time. As such, future analysis should include pure 2-
phenylethanol and pure, fresh 2-phenylethyl acetate.
Further, because the heating of the mixture was in a closed system, it is also
possible that the closed system is preventing the evaporation of 2-phenylethanol, and an
open system may need to be used in the future. Finally, it is possible that the lack of 2-
phenylethanol release was not due to any of these conditions, but that the headspace
analysis was not giving the mixture enough time to hydrolyze the ester bond. Thus, future
headspace analysis may include heating the sample for a longer time, or preparing the
sample a few hours beforehand to allow the mixture to hydrolyze longer.
In summary, a working understanding of the headspace apparatus was gained, and
directions for future work have been determined from this preliminary analysis
45
VI. FUTURE WORK
In the future there are various experiments that can be performed to expand on
this body of work.
Future Synthesis
Due to the inconclusive NMR results for compound (4), another larger scale
sequential Sonogashira coupling reaction should be conducted in order to obtain a yield
large enough for isolation. Various techniques of purification will be used to isolate the
tolane in order to isolate it to a desired purity level. Characterization of a pure sample
will allow comparison of the material recovered from other synthetic routes to a known
product. If the desired tolane is able to be isolated and characterized, the shorter one-pot
method of the Sonogashira reaction will be used to attempt to synthesize compound (4).10
If the one pot method is able to synthesize compound (4), then this would greatly reduce
the time required for overall synthesis. This also assumes that purification steps will not
be excessively more difficult than in the sequential method.
If the tolane can be completely isolated, a large enough quantity will be
synthesized in order to try to produce the ester-substituted hexaphenylbenzene, as seen by
Figure 6.1.
46
Figure 6.1. Ester substituted hexaphenylbenzene
Previous research students have synthesized a hexaphenylbenzene, for another project,
via a cobalt catalyzed cyclization reaction,6 which provide some insight on the laboratory
methods necessary to execute this scheme. Proposed work up to isolate the
hexaphenylbenzene would include flash chromatography, and column chromatography in
a 1:1 hexane/ethyl acetate system, as this solvent system has worked to isolate similar
product.11 Characterization will include TLC analysis, 1H NMR and 13C NMR, and
possibly liquid chromatography, as the molecular weight of the product will be too high
to be characterized via GC/MS. Headspace analysis via the method developed will be
47
used to determine if mild conditions are appropriate for slow release of volatiles.
If the hexaphenylbenzene can be synthesized and headspace analysis suggests that
the hexaphenylbenzene structure acts as an appropriate fragrance precursor, then attempts
will be made to attach other primary alcohols to compound (2), in particular citronellol,
another regularly used primary alcohol in industrial fragrance synthesis, as seen in Figure
6.2.1
O
O( )6
Figure 6.2. Substituted hexaphenylbenzene with citronellol ester bonding
Alternative Synthesis Routes
Another possible route that can be taken to create a less stable ester tolane
precursor is through the addition of an electron-withdrawing group, such as a nitro group,
on the ortho position of the phenyl ring relative to the carbonyl group. As shown in
Figure 6.3, the addition of a small electron-withdrawing group in this position may
destabilize the conjugation found in the molecule to the same degree as the methylene
spacer. Previous work by Murray et al. successfully synthesized a tolane similar in
structure to what is believed to be our alternate desired product.17
48
Figure 6.3. Proposed product with electron withdrawing groups in the ortho position
relative to the ester carbonyl group
A possible synthetic route, outlined in Scheme 6.1, may be possible based on knowledge
of basic organic chemistry and the synthetic method by Murray et al.
Scheme 6.1. Alternate synthetic route
As seen in Scheme 6.1, a commercially available reagent 4-Bromo-2-nitrobenzoic acid
(CAS # 99277-71-1) can ideally undergo a Fischer esterification utilizing silica chloride
49
catalyst18 with a primary alcohol, like 2-phenylethanol. Utilizing silica chloride catalyst
would limit the amount of water in the reaction, which will hopefully make the isolation
stage more straightforward. In the case of a Fischer esterification failing, a reaction with
thionyl chloride to produce an acid chloride intermediate would also esterify the carbonyl
group. Once the benzene has been esterified, it can then undergo the reaction conditions
described in Murray et al. with acetylene to create the desired tolane. Upon
characterization, the product will then be volatilized via headspace analysis to determine
how well it hydrolyzes the ester bond. If this analysis is deemed successful, cyclization to
the hexaphenylbenzene product will be attempted, but due to the location of electron
withdrawing groups this may interfere with the Co catalyst. Other electron withdrawing
groups such as ammonium, cyano groups, or trihalides could be used in place of the NO2
group.
50
VII. CONCLUSIONS
In summary, the industry of fragrances is constantly growing along with the
organic synthesis behind it. Through the utilization of organic synthesis, the application
of pro fragrances was yielded. Through our previous research on the synthesis of
hexaphenylbenzenes, we believed that these molecules could serve as an excellent
framework for pro fragrances. The purpose of this project was to synthesize a tolane
precursor capable of cyclization to a hexaphenylbenzene at a later date.
Though the synthesis of a spacer tolane was not conclusively confirmed, the
nuances and process by which this tolane can be produced was studied. This knowledge
will be extremely helpful in the future not only for this project, but for any other student
interested in synthesizing ester functionalized tolanes in the Ramey Research group.
Further, an original ester precursor molecule was created, teaching the concept of trial
and error in undergraduate research. A working knowledge of headspace analysis was
developed, and will be used in the future to analyze the tolane’s ability to release volatile
fragrant molecules.
Throughout this process, priceless knowledge of various synthetic techniques and
reactions were acquired, along with the ability to classically characterize synthetic
molecules. This experience has been invaluable to my learning and undergraduate
experience, and I highly recommend undergraduate research to anyone looking to gain
experience in converting intellectual knowledge of chemistry into its real world
applications.
51
VIII. REFERENCES
1. Sell, C. S., Chemistry of Fragrances: From Perfumer to Consumer; Ed. by
Charles S. Sell. Royal Society Of Chemistry: Cambridge, United Kingdom, 2006.
2. Fahlbusch, K. G.; Hammerschmidt, F. J.; Panten, J.; Pickenhagen, W.;
Schatkowski, D.; Bauer, K.; Garbe, D.; Surburg, H., Flavors and fragrances. Ullmann's
Encyclopedia of Industrial Chemistry 2003.
3. Herrmann, A., Controlled release of volatiles under mild reaction conditions:
From nature to everyday products. Angew. Chem.-Int. Edit. 2007, 46 (31), 5836-5863.
4. (a) Ashburn, J. G. Tobacco flavorants. 1963; (b) Teague, C. E. J. Tobacco. 1956.
5. Langer, R.; Peppas, N., Chemical and physical structure of polymers as carriers
for controlled release of bioactive agents: a review. Journal of Macromolecular Science-
Reviews in Macromolecular Chemistry and Physics 1983, 23 (1), 61-126.
6. Kobayashi, K.; Shirasaka, T.; Horn, E.; Furukawa, N., Two-dimensional
hexagonal hydrogen-bonded network with triangle-like large cavities: hexakis (4-
carboxyphenyl) benzene. Tetrahedron Letters 2000, 41 (1), 89-93.
7. Sonogashira, K.; Tohda, Y.; Hagihara, N., A convenient synthesis of acetylenes:
catalytic substitutions of acetylenic hydrogen with bromoalkenes, iodoarenes and
bromopyridines. Tetrahedron Letters 1975, 16 (50), 4467-4470.
8. Ramey, M. Synthesis of Variable Bandgap Conjugated Polyelectrolytes via Metal
Catalyzed Cross-coupling reactions. University of Florida, 2001.
9. Nagy, A.; Novak, Z.; Kotschy, A., Sequential and domino Sonogashira coupling:
Efficient tools for the synthesis of diarylalkynes. J. Organomet. Chem. 2005, 690 (20),
4453-4461.
10. Mio, M. J.; Kopel, L. C.; Braun, J. B.; Gadzikwa, T. L.; Hull, K. L.; Brisbois, R.
G.; Markworth, C. J.; Grieco, P. A., One-pot synthesis of symmetrical and unsymmetrical
bisarylethynes by a modification of the Sonogashira coupling reaction. Org. Lett. 2002, 4
(19), 3199-3202.
11. Jackson, K. Synthesis of Functionalized Tolanes In-Route to Hexaphenylbenzenes;
Appalachian State University: Boone, NC, 2008.
12. Epley, C. Synthesis of Functionalized tolanes; Appalachian State University:
52
2009.
13. Waybright, S. M.; Singleton, C. P.; Wachter, K.; Murphy, C. J.; Bunz, U. H.,
Oligonucleotide-directed assembly of materials: defined oligomers. Journal of the
American Chemical Society 2001, 123 (9), 1828-1833.
14. S. Inouye, S. S. Calcium-binding photoprotein, coelenterazine and imidazole
compound which removes NH-proton of pyrazine ring of imidazopyrazine. 2012.
15. Snow, N. H.; Slack, G. C., Head-space analysis in modern gas chromatography.
TrAC Trends in Analytical Chemistry 2002, 21 (9), 608-617.
16. Explanation of Dryer temperatures.
http://www.geappliances.com/search/fast/infobase/10000971.htm.
17. Murray, M. M.; Kaszynski, P.; Kaisaki, D. A.; Chang, W.; Dougherty, D. A.,
Prototypes for the polaronic ferromagnet. Synthesis and characterization of high-spin
organic polymers. Journal of the American Chemical Society 1994, 116 (18), 8152-8161.
18. Srinivas, K.; Mahender, I.; Das, B., Silica chloride: A versatile heterogeneous
catalyst for esterification and transesterification. Synthesis 2003, (16), 2479-2482.
53
IX. VITAE
Danielle Russell is a Pre-professional/Paramedical Chemistry major at
Appalachian State University. She currently resides in Charlotte North Carolina, though
her family hails from the Northern Colorado and Southern Wyoming area. Danielle and
her best friend Ishna like to eat brownies while making finger puppets for the puppetless
masses. Danielle loves living in the Boone area where she runs, hikes and engages in
general college shenanigans. Her ultimate goal is to go to medical school next year,
though life takes people on interesting journeys. Danielle would like to thank the Office
of Student Research for their partial funding and support of this project and her travels to
present on this body of work.
54
X. EXPERIMENTAL PROCEDURES
Instrumentation.
1H NMR spectra were obtained with a Varian Gemini 300MHz FT-NMR and Bruker
400 MHz FT-NMR. 13C NMR spectra were obtained with the same instruments, but at 75
MHz and 100 MHz respectively. Gas chromatography/mass spectrometry and headspace
(GC/MS) measurements were obtained with an Agilent 6890N GC network system
paired together with an Agilent 5973 inert mass selective detector that utilized a 30-meter
long Agilent DB-5MS column. The column used for headspace analysis was the same
type used for GC analysis, but was only 15 meters in length. One method was utilized for
GC analysis all precursors to the tolane molecule; The method utilizes an inlet
temperature of 200°C and an oven temperature of 50ºC, holding for 5 minutes, then
increasing at 10ºC per minute to 250ºC, holding at this temperature for 5 minutes, for a
total run time of 25.5 minutes.
Iodocarboxylic Acid Synthesis
(4-iodo-phenyl)-acetic acid (1) Based on an article by Waybright et al. and
synthesized by student Alex Cella. In a 500-mL round-bottomed flask, phenyl acetic acid
(15.21 g, 87.0 mmol) and iodine (14.25 g, 16.65 mmol) were dissolved in in 200 mL of
glacial acetic acid and stirred. To the stirred solution, a mixture of 5 mL conc. HNO3 and
20 mL of conc. H2SO4 was added drop wise over a 30 min. period. The mixture was then
stirred at 60° C for 1.5 hours, then removed from heat and left to stir overnight, where a
white precipitate formed. The mixture was then poured over 500 g of ice and vacuum
filtered. The pink solid was recovered and then recrystallized from hexanes to form
colorless needles (8.2 g, 45%). mp: 129°C. 1H NMR (300 MHz, CDCl3) 7.63 (d, 2H),
55
7.25 (d, 1H), 7.03 (s, 1H), 3.6 (s, 2H) ppm. 13C NMR (75 MHz, CDCl3) 177.25, 137.76,
132.77, 131.37, 93.00, 40.47 ppm. GC-MS Rt 18.23 min, single peak, M+ 262, 218, 90,
63
Diester Tolane Precursor synthesis
(4-iodo-phenyl)-acetic acid phenethyl ester (2). Procedure mimics a similar
synthesis, given in a patent by Inouye et al., a 50-mL side-armed pear-shaped flask
equipped with magnetic stir bar was flame dried and placed under vacuum and nitrogen.
After drying of the glassware, (4-iodo-phenyl)-acetic acid (1.0 g, 3.8 mmol) was added to
the flask. Then, thionyl chloride (3 mL, 41.4 mmol) was slowly added drop wise through
a syringe into the reaction mixture to yield a pale yellow solution. The reaction was
stirred for 2 hours at room temperature. The mixture was then cooled and concentrated by
reducing the pressure of the reaction mixture to remove excess thionyl chloride. To the
brown oily crude product, chilled 2-phenylethanol (0.5 mL, 4.2 mmol) was added drop
wise to the solution and allowed to stir under atmospheric conditions overnight. The
solution was then extracted with 15 mL of dichloromethane and 5 mL of 1 M sodium
hydroxide. After extraction, the solution was purified via flash chromatography
(methylene chloride). The product was a yellow viscous liquid (0.67 g, 48.2%). 1H
NMR (400 MHz, CDCl3) 7.68 (d, 2H), 7.29 (m, 5H), 7.01 (d, 2H), 4.34 (t, 2H), 3.56 (s,
2H), 2.94 (t, 2H) ppm. 13C NMR (100 MHz, CDCl3) 170.84, 137.64, 133.62, 131.34,
128.96, 128.45, 126.48, 92.59, 77.40, 76.98, 65.41, 40.92, 35.14 ppm. GC Rt 22.23 min,
single peak, MS: M+ 366, 261, 216, 104
56
(4-Ethynyl-phenyl)-acetic acid phenethyl ester. To a 50-mL side-armed round
bottom flask equipped with magnetic stir bar was added (4-iodo-phenyl)-acetic acid
phenethyl ester (1.07 g, 2.8 mmol) was then added. Then, 15 mL of triethylamine,
previously sparged with N2 was added via syringe to the reaction flask and allowed to
stir. The reaction flask was then heated to 60° C in an oil bath. CuI (0.03 g, 0.09 mmol)
and PdCl2 (0.05 g, 0.09 mmol) were then added to the solution. After addition of the
catalysts, trimethylsilylacetylene (0.31 g, 2.8 mmol) was slowly added drop wise and
allowed to stir in heat for 3 hours. After 3 hours the reaction was cooled to room
temperature, and was allowed to stir for 72 hours. The mixture was filtered and the
solvent was removed via rotary evaporation. The crude product was then extracted in 30
mL of dichloromethane, and washed in 15 mL of 6M HCl, water and brine solutions. The
organic layer was then dried over MgSO4. After drying, the crude product was purified
via flash chromatography on silica gel using dichloromethane as the solvent. The filtered
product was then evaporated down using rotary evaporation and dissolved in 5 mL of
terahydrofuran THF. To the dissolved solution, tetrabutylammonium fluoride (TBAF)
(2.84 mL, 3.7 mmol) was added drop wise and allowed to stir for one hour. THF was
then removed by rotary evaporation. Dichloromethane was then added and the solution
washed with 6M HCl, and water. The solvent was removed and product was recovered
(0.31 g, 53%). 1H NMR (300 MHz, CDCl3) 7.44 (d, 2H), 7.14 (m, 5H), 4.30 (t, 2H), 3.59
(s, 2H), 3.2(s, 1H), 2.9 (t, 2H) ppm. 13C NMR (300 MHz, CDCl3) 170.9, 137.6, 134.74,
132.28, 129.29, 128.87, 128.48, 126.56, 120.93, 83.39, 65.53, 53.39, 41.29, 35.00 ppm.
GC Rt 22.23 min, single peak, MS: M+ 264, 205, 160, 104
57
4-[4-(2-Phenylacetoxy-ethyl)-phenylethynyl]-phenyl-acetic acid phenethyl
ester To a 50-mL side-arm round bottom flask equipped with magnetic stir bar (4-
Ethynyl-phenyl)-acetic acid phenethyl ester (0.11 g, 0.41 mmol) was added. Then, 10 mL
of triethylamine, previously sparged with N2 was added via syringe to the reaction flask
and allowed to stir. The reaction flask was then heated to 60° C in an oil bath. CuI (0.002
g, 0.003 mmol) and PdCl2 (0.01 g, 0.003 mmol) were then added to the solution. After
addition of the catalysts, (4-iodo-phenyl)-acetic acid phenethyl ester (0.15 g, 0.41 mmol)
was slowly added drop wise and allowed to stir in heat for 3 hours. After 3 hours the heat
was removed and the mixture was allowed to stir at room temperature for 72 hours. The
mixture was filtered and the solvent was removed via rotary evaporation. The crude
product was then extracted with 15 mL of dichloromethane, and washed with 5 mL of
6M HCl, water, and brine solutions. The organic layer was then dried over MgSO4. After
drying, the crude product was purified via flash chromatography on silica gel in
dichloromethane and then dried over MgSO4. Product was not pure at this stage
preliminarily. 1H NMR results and assignments are presented in Appendix I.
58
Appendix
GC/MS DATA
Mass Spectroscopy of (4-iodo-phenyl)-acetic acid Gas Chromatograph of (4-iodo-phenyl)-acetic acid
4 .00 6 .00 8 .00 10 .00 12 .00 14 .00 16 .00 18 .00 20 .00 22 .00 24 .00 26 .00 28 .00
500000
1000000
1500000
2000000
2500000
3000000
3500000
4000000
4500000
5000000
5500000
6000000
6500000
T ime-->
A bundanc e
T IC: iodophenylac e tic ac id .D \ da ta .ms
60 80 100 120 140 160 180 200 220 240 2600
5000
10000
15000
20000
25000
30000
35000
40000
45000
50000
55000
60000
m/ z-->
Abundance
Scan 2064 (14.291 min): iodophenylaceticacid.D\ data.ms261.9216.9
90.0
63.0
126.8107.1 243.8164.7
59
Mass Spectroscopy of (4-iodo-phenyl)-acetic acid phenethyl ester
Gas Chromatograph of (4-iodo-phenyl)-acetic acid phenethyl ester
6 0 8 0 1 0 0 1 2 0 1 4 0 1 6 0 1 8 0 2 0 0 2 2 0 2 4 0 2 6 0 2 8 0 3 0 0 3 2 0 3 4 0 3 6 00
2 0 0 0 0 0
4 0 0 0 0 0
6 0 0 0 0 0
8 0 0 0 0 0
1 0 0 0 0 0 0
1 2 0 0 0 0 0
1 4 0 0 0 0 0
1 6 0 0 0 0 0
1 8 0 0 0 0 0
2 0 0 0 0 0 0
2 2 0 0 0 0 0
2 4 0 0 0 0 0
2 6 0 0 0 0 0
2 8 0 0 0 0 0
3 0 0 0 0 0 0
3 2 0 0 0 0 0
3 4 0 0 0 0 0
3 6 0 0 0 0 0
m/ z-->
A b u n d a n c e
S c a n 3 4 3 8 (2 1 .4 2 0 min ): io d o sp a c e re ste r.D \ d a ta .ms1 0 4 .0
2 1 6 .9
2 6 1 .9
7 7 .05 1 .0 1 6 7 .11 2 6 .9 3 6 6 .01 9 1 .0 2 9 2 .9 3 3 7 .0
4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00 24.00 26.00 28.00
2000000
4000000
6000000
8000000
1e+07
1.2e+07
1.4e+07
Time-->
Abundance
TIC: iodospacerester.D\data.ms
60
Mass Spectroscopy of (4-Ethynyl-phenyl)-acetic acid phenethyl ester Gas Chromatograph of of (4-Ethynyl-phenyl)-acetic acid phenethyl ester
6 0 8 0 1 0 0 1 2 0 1 4 0 1 6 0 1 8 0 2 0 0 2 2 0 2 4 0 2 6 0 2 8 00
5 0 0 0
1 0 0 0 0
1 5 0 0 0
2 0 0 0 0
2 5 0 0 0
3 0 0 0 0
3 5 0 0 0
4 0 0 0 0
4 5 0 0 0
m / z -->
A b u n d a n c e
S c a n 3 0 6 7 (1 9 .4 9 5 m in ): tb a fc o lu m n e d h a c e ty le s te r.D \ d a ta .m s1 0 4 .0
2 0 5 .11 6 0 .0
2 6 4 .17 7 .0
5 1 .01 2 7 .8 2 8 1 .01 7 7 .9
4.00 6.00 8.00 10.00 12.00 14.00 16.00 18.00 20.00 22.00 24.00 26.00 28.000
500000
1000000
1500000
2000000
2500000
3000000
3500000
4000000
Time-->
Abundance
TIC: tbafcolumnedhacetylester.D\data.ms
61
HEADSPACE ANALYSIS
Gas chromatograph of stock 2-phenylethanol
Mass spectrum of stock 2-phenylethanol
4 .0 0 5 .0 0 6 .0 0 7 .0 0 8 .0 0 9 .0 0 1 0 .0 0 1 1 .0 0 1 2 .0 0 1 3 .0 00
5 0 0 0 0 0
1 0 0 0 0 0 0
1 5 0 0 0 0 0
2 0 0 0 0 0 0
2 5 0 0 0 0 0
3 0 0 0 0 0 0
3 5 0 0 0 0 0
4 0 0 0 0 0 0
4 5 0 0 0 0 0
5 0 0 0 0 0 0
5 5 0 0 0 0 0
6 0 0 0 0 0 0
T im e -->
A b u n d a n c e
T IC : 2 p h e n y e th a n o lh y d ro .D \ d a ta .m s
3 .2 2 0 3 .2 3 8 3 .2 7 4 3 .3 2 4 3 .3 4 9 3 .4 0 7 3 .4 5 5 3 .4 9 3 3 .5 2 1 3 .5 4 5 3 .5 6 7 3 .6 0 3 3 .6 2 6 3 .6 6 5 3 .7 7 5 3 .8 5 7 3 .9 2 1 4 .0 0 6 4 .0 5 9 4 .1 1 0 4 .1 4 1 4 .1 9 9 4 .2 1 6 4 .2 3 5 4 .2 8 9 4 .3 1 2 4 .3 7 9 4 .4 3 1 4 .5 4 6 4 .5 8 6 4 .6 0 9
4 .7 3 3
4 .9 4 9 4 .9 8 8 5 .0 7 4 5 .1 0 2 5 .1 5 5 5 .1 9 4 5 .2 9 4 5 .3 8 1
5 .4 9 4
5 .5 5 0 5 .6 2 8 5 .6 6 5 5 .7 0 3 5 .7 3 3 5 .7 8 0 5 .8 0 4 5 .8 5 1 5 .9 1 4 5 .9 4 3 5 .9 7 4 6 .0 3 2 6 .0 5 6 6 .1 0 4 6 .1 6 1 6 .1 8 1 6 .1 9 9 6 .2 6 6 6 .2 9 6 6 .3 2 4 6 .3 7 8 6 .4 0 1 6 .4 6 4 6 .5 0 6 6 .5 5 3 6 .6 5 5 6 .7 1 3 6 .7 5 4 6 .8 0 9 6 .9 0 1 6 .9 4 5 7 .0 0 1 7 .0 5 2 7 .1 0 7 7 .1 7 0 7 .2 3 4 7 .2 7 6 7 .2 9 8 7 .3 7 9 7 .4 6 3 7 .4 9 6 7 .5 4 5 7 .5 7 6 7 .6 6 4 7 .7 1 0 7 .7 4 0 7 .7 6 5 7 .8 2 1 7 .9 1 5 7 .9 6 1 7 .9 9 3 8 .0 4 9 8 .2 5 3 8 .3 7 5 8 .4 8 8 8 .5 8 2 8 .6 2 8 8 .6 5 5 8 .7 1 7 8 .9 6 7 9 .0 5 1 9 .3 4 0 9 .5 7 9 9 .9 0 51 0 .0 7 91 0 .1 4 91 0 .1 9 11 0 .2 1 41 0 .2 4 61 0 .3 1 81 0 .5 7 51 0 .6 8 91 1 .0 9 71 1 .6 7 01 2 .5 0 61 2 .5 3 31 2 .6 4 41 3 .3 8 31 3 .4 0 61 3 .4 9 71 3 .5 9 8
4 5 5 0 5 5 6 0 6 5 7 0 7 5 8 0 8 5 9 0 9 5 1 0 0 1 0 5 1 1 0 1 1 5 1 2 0 1 2 5 1 3 00
1 0 0 0 0 0
2 0 0 0 0 0
3 0 0 0 0 0
4 0 0 0 0 0
5 0 0 0 0 0
6 0 0 0 0 0
7 0 0 0 0 0
8 0 0 0 0 0
9 0 0 0 0 0
1 0 0 0 0 0 0
1 1 0 0 0 0 0
1 2 0 0 0 0 0
1 3 0 0 0 0 0
1 4 0 0 0 0 0
1 5 0 0 0 0 0
1 6 0 0 0 0 0
m / z - - >
A b u n d a n c e
S c a n 2 8 3 ( 4 . 7 0 0 m i n ) : 2 p h e n y e t h a n o l h y d r o . D \ d a t a . m s9 1 . 1
1 2 2 . 1
6 5 . 0
7 7 . 05 1 . 01 0 3 . 0
8 4 . 0
62
Gas chromatograph of stockroom 2-phenylethylacetate
Mass spectrum of peak at RT 4.652 minutes stockroom sample
4.00 5.00 6.00 7.00 8.00 9.00 10.00 11.00 12.00 13.000
1000000
2000000
3000000
4000000
5000000
6000000
7000000
8000000
Time-->
Abundance
TIC: phenethylacetatehydrostraight.D\ data.ms
3.223 3.759 4.135
4.652
4.773 4.839 4.872 4.967 5.012 5.034 5.139 5.196 5.267 5.314 5.347 5.385 5.412 5.443 5.481 5.832 6.062 6.392
6.618
6.785 6.806 6.827 6.847 6.905 6.922 6.961 6.995 7.019 7.059 7.229 7.273 7.307 7.335 7.393 7.426 7.485 7.524 7.586 7.615 7.640 7.677 7.802 7.949 8.041 8.305 8.355 8.463 8.961 9.335 9.398 9.453 9.856 9.94910.707 13.58913.606
45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 1300
20000
40000
60000
80000
100000
120000
140000
160000
180000
200000
220000
m/ z-->
Abundance
Scan 273 (4.643 min): phenethylacetatehydrostraight.D\ data.ms91.0
122.0
65.0
51.0 77.0 103.0
63
Mass spectrum of peak at RT 6.618 mintues in stockroom 2-phenylethyl acetate sample
Gas chromatograph of of mixture of 1 mL stock 2-phenethyl acetate, 1 ml DI water
50 60 70 80 90 100 110 120 130 140 150 160 1700
500000
1000000
1500000
2000000
2500000
3000000
3500000
m/z-->
Abundance
Scan 613 (6.589 min): phenethylacetatehydrostraight.D\data.ms104.1
91.1
65.1 78.151.1121.1 131.0 163.0145.0
4.00 5.00 6.00 7.00 8.00 9.00 10.00 11.00 12.00 13.000
1000000
2000000
3000000
4000000
5000000
6000000
7000000
8000000
Time-->
Abundance
TIC: phenethylacetatehydrohydro.D\ data.ms
3.216 3.753 4.138 4.650 4.792 4.838 4.926 4.969 5.029 5.098 5.117 5.184 5.310 5.366 5.478 5.544 5.857 6.389
6.620
6.814 6.837 6.887 6.927 6.965 6.994 7.014 7.047 7.171 7.226 7.346 7.391 7.452 7.487 7.517 7.575 7.610 7.660 7.700 7.743 7.801 7.948 8.043 8.319 8.353 8.467 8.516 8.961 9.306 9.393 9.450 9.681 9.852 9.94710.70311.400 13.594
64
Gas chromatograph of 1 mL of 2-phenethyl acetate, 1 mL DI water, 2 drops conc HCl
Gas chromatograph of 1 mL 2-phenethyl acetate, 1 mL DI water, 1 mL 1M HCl
2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 11.00 12.00 13.000
100000
200000
300000
400000
500000
600000
700000
800000
900000
1000000
1100000
1200000
Time-->
Abundance
TIC: with 2 drops conc acid.D\ data.ms
1.124 1.171 1.218 1.410 1.495 1.530 1.573 2.831
3.029 3.243 3.780 4.122 4.158
4.669
4.792 4.847 4.910 4.954 4.988 5.031 5.060 5.094 5.147 5.178 5.221 5.326 5.456 5.493 5.872 6.402
6.631
6.821 6.863 6.898 6.959 6.981 7.023 7.053 7.206 7.240 7.277 7.324 7.418 7.449 7.516 7.563 7.597 7.721 7.738 7.771 7.807 7.917 7.959 7.993 8.050 8.139 8.220 8.241 8.319 8.367 8.407 8.470 8.520 8.641 8.733 8.790 8.973 9.213 9.338 9.393 9.463 9.575 9.690 9.793 9.864 9.95410.70910.88011.41511.74312.22212.27212.30112.81412.91613.49513.55513.60413.64413.80313.83113.90713.938
1.00 2.00 3.00 4.00 5.00 6.00 7.00 8.00 9.00 10.00 11.00 12.00 13.000
100000
200000
300000
400000
500000
600000
700000
800000
900000
1000000
1100000
Time-->
Abundance
TIC: 1 mL 1 M acid.D\data.ms
0.554 0.580 0.629 0.646 0.747 0.776 0.884 0.900 0.925 0.967 1.083
2.810 3.227 3.762 4.146
4.656
4.837 4.865 4.909 4.942 4.967 5.016 5.068 5.112 5.171 5.315 5.484 5.864 6.395 6.484
6.624
6.802 6.851 6.916 6.963 6.996 7.032 7.071 7.126 7.150 7.169 7.200 7.227 7.288 7.393 7.474 7.526 7.550 7.598 7.709 7.760 7.802 7.848 7.928 7.977 8.043 8.156 8.215 8.234 8.264 8.304 8.339 8.354 8.462 8.680 8.733 8.962 9.028 9.118 9.172 9.392 9.454 9.682 9.858 9.95110.696 13.601
65
Gas chromatograph of 1 mL 2-phenethyl acetate, 1 mL DI water, 1 mL of 6M HCl
4.00 5.00 6.00 7.00 8.00 9.00 10.00 11.00 12.00 13.00
0
100000
200000
300000
400000
500000
600000
700000
800000
900000
1000000
1100000
1200000
T ime-->
Abundanc e
T IC: 6M H Cl 1 mL.D \ data.ms
3.777 4.119 4.155
4.664
4.837 4.877 4.916 4.981 5.022 5.090 5.114 5.137 5.211 5.241 5.321 5.413 5.491 5.561 5.628 5.682 5.836 5.870 5.983 6.018 6.358 6.399 6.464
6.628
6.865 6.891 6.919 7.055 7.076 7.099 7.139 7.231 7.287 7.358 7.392 7.466 7.696 7.728 7.802 7.862 7.941 7.985 8.046 8.164 8.229 8.278 8.311 8.339 8.364 8.406 8.468 8.531 8.717 8.736 8.963 9.006 9.207 9.333 9.399 9.456 9.573 9.691 9.857 9.951 10.84610.88710.91810.94610.98511.01911.08711.10511.15711.18211.23111.33011.34711.40911.42811.50011.65711.69411.827 12.72513.43913.60513.80513.908
66
NMR DATA
1H NMR of (4-iodo-phenyl)-acetic acid phenethyl ester (CDCl3)
67
13C NMR of (4-iodo-phenyl)-acetic acid phenethyl ester (CDCl3)
68
1H NMR of (4-Ethynyl-phenyl)-acetic acid phenethyl ester (CDCl3)
69
13C NMR of (4-Ethynyl-phenyl)-acetic acid phenethyl ester (CDCl3)
f
70
13C NMR of 4-[4-(2-Phenylacetoxy-ethyl)-phenylethynyl]-phenyl-acetic acid phenethyl ester (CDCl3)
71