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AQA A2 CHEMISTRY

TOPIC 4.10

ORGANIC SYNTHESIS AND ANALYSIS

TOPIC 4.11

STRUCTURE DETERMINATION

BOOKLET OF PAST EXAMINATION QUESTIONS

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1. Consider the following reaction sequence.

C H 3 C H 3

N O 2

C H 3

N H 2

m e t h y l b e n z e n e E F

S t e p S t e p 2

!a" #or Step $ name the mechanism and gi%e the reagents in%ol%ed.

Name of mechanism ................................................................................................

Reagents .................................................................................................................

....................................................................................................................................

(3)

!b" #or Step 2$ gi%e a reagent or combination of reagents. &rite an equation for this reaction

using 'H( to represent the reductant.

Reagent(s) .................................................................................................................

Equation .................................................................................................................

(2)

!c" )i%e the m/z %alue of a ma*or pea+ which could appear in the mass spectrum of

methylbenzene$ but not in the spectrum of either E or F.

.....................................................................................................................................(1)

!d" ,raw the structure of the species formed by F in an e-cess of hydrochloric acid.

(1)

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!e" Compounds G and H are both monosubstituted benzenes and both are isomers of F. G is

a primary amine and H is a secondary amine. ,raw the structures of G and Hbelow.

G

H

(2)

(T!"# $ %"&')

2. !a" &rite an equation for the formation of methyl propanoate$ CH3CH

2COOCH

3$ from

methanol and propanoic acid.

....................................................................................................................................(1)

!b" Name and outline a mechanism for the reaction between methanol and propanoyl chloride

to form methyl propanoate.

Name of mechanism ..................................................................................................

Mechanism

()

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!c" ropanoic anhydride could be used instead of propanoyl chloride in the preparation of

methyl propanoate from methanol. ,raw the structure of propanoic anhydride.

(1)

!d" !i" )i%e *+ad%antage of the use of propanoyl chloride instead of propanoic acid in

the laboratory preparation of methyl propanoate from methanol.

...........................................................................................................................

...........................................................................................................................

!ii" )i%e *+ad%antage of the use of propanoic anhydride instead of propanoylchloride in the industrial manufacture of methyl propanoate from methanol.

...........................................................................................................................

...........................................................................................................................(2)

!e" /n ester contains a benzene ring. 0he mass spectrum of this ester shows a molecular ion

pea+ at m/z 1 3.

!i" ,educe the molecular formula of this ester.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

!ii" ,raw !,possible structures for this ester.

(3)

(T!"# 12 %"&')

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3. Compound U is shown below.

C H C H C H C

O

C l3 2 2

!a" Name compound U.

.....................................................................................................................................(1)

!b" !i" State why the mass spectrum of U contains two molecular ion pea+s.

.......................................................................................................................

!ii" )i%e the m/z %alues of these two pea+s.

.......................................................................................................................

.......................................................................................................................(2)

!c" Name and outline a mechanism for the reaction of U with CH3OH

Name of mechanism ....................................................................................................

Mechanism

()

(T!"# - %"&')

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4. 0he proton n.m.r. spectrum of compound Xis shown below.

4

.3

4

.2

4

.

4

.5

3

.6

3.7

3

.8

3

.

3

.9

3

.4

3

.3

3

.2

3

.

3

.5

2

.6

2

.7

2

.8

2

.

2

.9

2

.4

2

.3

2

.2

2

.

2

.5

.6

.7

.8

.

.9

.4

.3

.2

C

h

e

m

ic

a

l

sh

ift$

:p

p

m

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Compound X$ C8H

2O

3$ contains both a +etone and an ester functional group. 0he measured

integration trace for the pea+s in the n.m.r. spectrum of X gi%es the ratio shown in the table

below.

Chemical shift$ :ppm 4.3 2.8 2.98 2.25 .2

;ntegration ratio 5.7 5.7 5.7 .2 .2

number ratio of each type of proton in compound X=

...............................................................................................................................(1)

!c" ,raw the part of the structure of X which can be deduced from the presence of the pea+ at

2.25.

................................................................................................................................(1)

!d" 0he pea+s at 4.3 and .2 arise from the presence of an al+yl group. ;dentify the

group and e-plain the splitting pattern.

Alkyl group .............................................................................................................

Explanation .............................................................................................................

.................................................................................................................................

.................................................................................................................................(3)

!e" ,raw the part of the structure of X which can be deduced from the splitting of the pea+s

at 2.8 and 2.98.

.................................................................................................................................(1)

!f" ,educe the structure of compound X.

.................................................................................................................................(2)

(T!"# $ %"&')

. Compound Q has the molecular formula C4H

8ClO and does not produce misty fumes when

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added to water.

!a" 0he infra>red spectrum of Q contains a ma*or absorption at 824 cm?

. ;dentify the bond

responsible for this absorption.

.....................................................................................................................................(1)

!b" 0he mass spectrum of Q contains two molecular ion pea+s at m:z 1 5 and m:z 1 57.

;t also has a ma*or pea+ at m:z 1 43.

!i" Suggest why there are two molecular ion pea+s.

...........................................................................................................................

!ii" / fragment ion produced from Q has m:z 1 43 and contains atoms of !&++

different elements. ;dentify this fragment ion and write an equation showing its

formation from the molecular ion of Q.

Fragment ion ....................................................................................................

Equation ...........................................................................................................(3)

!c" 0he proton n.m.r. spectrum of Q was recorded.

!i" Suggest a suitable sol%ent for use in recording this spectrum of Q.

...........................................................................................................................

!ii" )i%e the formula of the standard reference compound used in recording proton

n.m.r. spectra.

...........................................................................................................................(2)

!d" 0he proton n.m.r. spectrum of Q shows three pea+s. Complete the table below to show

the number of ad*acent$ non>equi%alent protons responsible for the splitting pattern.

ea+ ea+ 2 ea+ 3

;ntegration %alue 3 3

Splitting pattern doublet singlet quartet

Number of ad*acent$

non>equi%alent protons

(1)

!e" @sing the information in parts !a"$ !b" and !d"$ deduce the structure of compound Q.

(1)

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!f" / structural isomer of Q reacts with cold water to produce misty fumes. Suggest a

structure for this isomer.

(1)

(T!"# $ %"&')

/. !a" ,raw the structure of ethyl propanoate.

(1)

!b" Name and outline a mechanism for the formation of ethyl propanoate from propanoyl

chloride and ethanol.

Name of mechanism...............................................................................................

Mechanism

()

!c" 0he mass spectrum of ethyl propanoate contains a ma*or pea+ at m/z 1 98. &rite an

equation showing the fragmentation of the molecular ion to form the species responsible

for the pea+ at m/z 1 98. Show the structure of this species in your answer.

................................................................................................................................(2)

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!d" ,raw the structure of another ester which is an isomer of ethyl propanoate and which

gi%es a ma*or pea+ at m/z 1 8 in its mass spectrum.

(1)

(T!"# $ %"&')

. !a" !i" @sing mass spectrometry$ what information in addition toMrcan be obtained from

the precise %alue of the mass of the molecular ion of an organic compound=

............................................................................................................................

!ii" Suggest why$ for most organic compounds$ it is possible to detect a pea+ at onemass unit higher than that of the molecular ion.

............................................................................................................................(2)

!b" #ragmentation of the molecular ion of methylbutanone$ !CH3"2CHCOCH

3$ gi%es rise to

dominant pea+s at m/z1 8 and m/z43.

!i" Construct a balanced equation to show how fragmentation of the molecular ion

gi%es rise to the pea+ at m/z1 8.

...........................................................................................................................

...........................................................................................................................

!ii" ;n the fragmentation of !CH3"2CHCOCH

3$ two fragments with m/z 43 are formed.

)i%e the structural formula of each of these fragments.

tructure ! tructure "

()

!c" 0wo molecular ion pea+s appear in the mass spectrum of 2>chloropropane at m/z87

and m/z1 75. A-plain why two molecular ion pea+s are found and why the relati%e

intensities of the pea+s are appro-imately 3 to $ respecti%ely.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(3)

(T!"# 10 %"&')

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-. 0hree sections of the proton n.m.r. spectrum of CH3CHClCOOH are shown below.

2 . 5 . 5 5 . 5 4 . 4 . 9 4 . 4 4 . 3 . 7 . 8 .

: p p m : p p m : p p m

!a" Name the compound CH3CHClCOOH

................................................................................................................................(1)

!b" A-plain the splitting patterns in the pea+s at .82 and 4.44

................................................................................................................................

................................................................................................................................

................................................................................................................................(2)

!c" redict the splitting pattern that would be seen in the proton n.m.r. spectrum of the

isomeric compound ClCH2CH

2COOH

................................................................................................................................

................................................................................................................................(1)

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!d" 0he amino acid alanine is formed by the reaction of CH3CHClCOOH with an e-cess of

ammonia. 0he mechanism is nucleophilic substitution. Outline this mechanism$ showing

clearly the structure of alanine.

()

!e" 0he amino acid lysine has the structure

H

! C H "H N

N H

C C O O H2 2

2

4

,raw structures to show the product formed in each case when lysine reacts with

!i" an e-cess of aqueous HCl$

!ii" an e-cess of aqueous NaOH$

!iii" another molecule of lysine.

(3)

(T!"# 12 %"&')

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$. !a" !i" &rite an equation for the reduction of pentan>2>one by aqueous NaBH4to form

pentan>2>ol.

@se 'H( to represent the reductant.

.....................................................................................................................

!ii" Name and outline a mechanism for this reduction.

Name of mechanism ....................................................................................

Mechanism

!iii" State why the pentan>2>ol produced in this reaction is not optically acti%e.

.....................................................................................................................()

!b" redict the m/z %alues of the two most abundant fragments in the mass spectrum of

pentan>2>one.

Fragment ! .............................................................................................................

Fragment " .............................................................................................................(2)

(T!"# $ %"&')

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10. Spectral data for use in this question are pro%ided below the eriodic 0able !first item on the

database".

Compound Qhas the molecular formula C4H

7O

2

!a" 0he infra>red spectrum of Qis shown below.

5 5

9 5

5

4 5 5 5 3 5 5 5 2 5 5 5 9 5 5 5 5 5 9 5 5

& a % e n u m b e r : c m

0

ra

n

sm

itta

n

c

e

:

R S

?

;dentify the type of bond causing the absorption labelled Rand that causing the

absorption labelled S.

R............................................................................................................................

S.............................................................................................................................(2)

!b" Qdoes not react with 0ollensD reagent or #ehlingDs solution. ;dentify a functional group

which would react with these reagents and therefore cannot be present in Q.

...............................................................................................................................(1)

!c" roton n.m.r. spectra are recorded using a solution of a substance to which

tetramethylsilane !0ES" has been added.

!i" )i%e two reasons why 0ES is a suitable standard.

Reason ! #######################################################################################################

Reason ".......................................................................................................

!ii" )i%e an e-ample of a sol%ent which is suitable for use in recording an n.m.r.

spectrum. )i%e a reason for your choice.

ol$ent ..........................................................................................................

Reason .......................................................................................................... (4)

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!d" 0he proton n.m.r. spectrum of Qshows 4 pea+s.

0he table below gi%es %alues for each of these pea+s together with their splitting

patterns and integration %alues.

:ppm 2.25 2.6 3.45 3.74

Splitting pattern singlet triplet singlet triplet

;ntegration %alue 3 2 2

&hat can be deduced about the structure of Qfrom the presence of the following in its

n.m.r. spectrum=

!i" 0he singlet pea+ at 1 2.25

.....................................................................................................................

!ii" 0he singlet pea+ at 1 3.45

.....................................................................................................................

!iii" 0wo triplet pea+s

.....................................................................................................................(3)

!e" @sing your answers to parts !a"$ !b" and !d"$ deduce the structure of compound Q.

(1)

(T!"# 11 %"&')

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11. Consider the reaction scheme below which starts from butanone.

H C C C H C H H

H

C

C

C

C

C H

C H

C H

C H

3 2 2

2

2 4

3 3

3

3

3

O

C N

H

O H

O H

< e a c t i o n

< e a c t i o n 2

e - c e s sc o n c $ H S O

7 5 F Cb u t ? ? e n e a n d b u t ? 2 ? e n e

A

B

!a" !i" )i%e a suitable reagent for

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!b" !i" )i%e a suitable reagent for red absorption data below$ describe the two ma*or

differences between the infra>red spectra of butanone and of B.(4)

!c" Outline a mechanism for the formation of but>>ene by the dehydration of B.

(4)

!d" ,raw the structure of the repeating unit in the polymer which can be formed from

but>>ene.

(1)

(T!"# 1 %"&')

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12. 0he proton n.m.r. spectrum of an ester$ A$ is shown below.

4 3 2

Chemical shift$ :ppm

0he measured integration trace gi%es the ratio 5.95 to 5.95 to 5.89 to 5.89 for the pea+s at

4.3$ 2.32$ .33 and .56$ respecti%ely.

!a" 0he mass spectrum of compound Ahas a molecular ion pea+ at m/z1 52.

,educe the molecular formula of compound A.

.....................................................................................................................................

.....................................................................................................................................

..................................................................................................................................... (3)

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!b" &hat is the ratio of the numbers of each type of proton=

.....................................................................................................................................(1)

!c" &hat can be deduced about the arrangement of protons from the splitting patterns in the

n.m.r. spectrum=

.....................................................................................................................................(1)

!d" ,educe the structure of compound Aand label with the letters a$ b$ c and d the four

groups of equi%alent protons.

(1)

!e" /ssign the %arious signals in the table below to the groups of protons in compound A

pre%iously labelled a$ b$ c and d.

Chemical shift$ :ppm .56 .33 2.32 4.3

Gabel of group

(4)

(T!"# 10 %"&')

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13. 0he proton n.m.r. spectrum of an alcohol$ A$ C9H

2O$ is shown below

. 7 . . 4 . 2 . 5 5 . 7 5 . 5 . 4 5 . 2 5

: p p m

0he measured integration trace gi%es the ratio 5.65 to 5.49 to 2.85 to .39 for the pea+s at

.92$ .36$ .2 and 5.63$ respecti%ely.

!a" &hat compound is responsible for the signal at 5=

.....................................................................................................................................(1)

!b" How many different types of proton are present in compound A=

.....................................................................................................................................(1)

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!c" &hat is the ratio of the numbers of each type of proton=

.....................................................................................................................................(1)

!d" 0he pea+s at .92 and 5.63 arise from the presence of a single al+yl group. ;dentify

this group and e-plain the splitting pattern.

&roup#.........................................................................................................................

Explanation##########.......................................................................................................

.....................................................................................................................................(3)

!e" &hat can be deduced from the single pea+ at .2 and its integration %alue=

.....................................................................................................................................(1)

!f" )i%e the structure of compound /.

(1)

(T!"# - %"&')

14. 0he ester formed when ethanol reacts with ethanoic anhydride was analysed by high>resolution proton n.m.r. spectroscopy.

!i" )i%e the structural formula of the ester.

!ii" How many different types of proton are present in this ester=

............................................................................................................................

!iii" ,escribe the splitting pattern of the ethyl group in the n.m.r. spectrum of the ester.

............................................................................................................................(3)

(T!"# 3 %"&')

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1. !a" ,efine the termstructural isomerism.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

!b" 0he graph below shows part of the mass spectrum of an organic compound$ A$ which has

the molecular formula C4H

5.

r e l a t i % ea b u n d a n c e

5 5 2 5 3 5 4 5 9 5 5 m : e

!i" ,raw graphical formulae for the structural isomers of C4H

5.

;somer ;somer 2

(2)

!ii" Suggest the formula of the fragment that corresponds to each of the following m:e

%alues shown in the mass spectrum of compound A.

43 ......................................................................................................................

26 ......................................................................................................................

9 ......................................................................................................................(3)

!iii" ,educe which of the isomers drawn in !i" corresponds to compound A. )i%e a

reason for your answer.

...........................................................................................................................

...........................................................................................................................(2)

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!c" !i" Suggest graphical formulae for !, structural isomers with the molecular formula

C3H

O

2. Aach isomer contains a single functional group. 0he functional groups are

different in the two isomers.

I%+& 3 I%+& 4

(2)

!ii" )i%e the name of the type of compound that each isomer represents.

;somer 3 ............................................................................................................

;somer 4 ............................................................................................................(2)

(T!"# 13 %"&')

1/. Aach of the parts !a" to !f" below concerns a different pair of isomers. ,educe one possible

structural formula for each of the species Ato L.

!a" Aand Bha%e the molecular formula C2H

4O

2. /n aqueous solution of Areacts with

calcium carbonate to liberate carbon dio-ide$ but Bdoes not.

A B

(2)

!b" Cand Dha%e the molecular formula C3H

7O. Chas a broad absorption band at

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3355 cm?

in its infra>red spectrum$ but Ddoes not.

C D

(2)

!c" Eand Fha%e the molecular formula C3H

C

2. Ehas only one pea+ in its low resolution

proton n.m.r. spectrum but Fhas two.

E F

(2)

!d" Gand Hha%e the molecular formula C3H

O and both ha%e strong absorption bands at

about 855 cm?

in their infra>red spectra. Gturns acidified potassium dichromate!;"

solution green but Hdoes not.

G H

(2)

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!e" Iand ha%e the molecular formula C4H

6Br. Ishows optical acti%ity$ but does not.

I

(2)

!f" Kand Lha%e the molecular formula C9H

5. Khas a wea+ absorption band at

95 cm?

in its infra>red spectrum$ but L does not.

K L

(2)(T!"# 12 %"&')

1. !a" Name and outline a mechanism for the reaction between propanone and hydrogen

cyanide.

Name ..........................................................................................................................

Mechanism

()

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!b" Carbonyl compounds can be reduced to alcohols.

!i" &rite an equation for the reduction of propanone to the corresponding alcohol and

identify a suitable reducing agent. ;n the equation you may use the symbol 'H( for

the reducing agent.

Equation ............................................................................................................

Re'ucing agent.................................................................................................

!ii" 0wo isomeric carbonyl compounds$ Aand B$ with molecular formula C4H

7O both

ha%e 3 pea+s in their low>resolution proton n.m.r. spectra.

resolution proton

n.m.r. spectrum whereas reduction of Bforms alcohol Dwhich has 4 pea+s in its

low>resolution proton n.m.r. spectrum.

,raw one possible structure for each of these 4 compounds.

aronyl compoun'A AlcoholC

aronyl compoun'B Alcohol D

(/)

(T!"# 11 %"&')

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1-. Compound A$ C9H

5O$ reacts with NaBH

4to gi%e B$ C

9H

2O. 0reatment of Bwith concentrated

sulphuric acid yields compound C$ C9H

5. /cid>catalysed hydration of Cgi%es a mi-ture of

isomers$ Band D.

#ragmentation of the molecular ion of A$ 'C9

H5

O(I

$ leads to a mass spectrum with a ma*or

pea+ at m/z98. 0he infra>red spectrum of compound Ahas a strong band at 89 cm?

and the

infra>red spectrum of compound Bhas a broad absorption at 3395 cm?

!0able". 0he proton

n.m.r. spectrum of Ahas two signals at .5 !triplet" and 2.42 !quartet"$ respecti%ely

!Spectrum".

@se the analytical and chemical information pro%ided to deduce structures for compounds A$ B$

Cand D$ respecti%ely. ;nclude in your answer an equation for the fragmentation of the

molecular ion of Aand account for the appearance of the proton n.m.r. spectrum of A. A-plain

why isomers Band Dare formed from compound C.

S+!&%

4 2 5 : p p m

C o m p o u n d $ C H OA 9 5

(T!"# 20 %"&')

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1$. !a" 0he infra>red spectrum of compound A$ C3H

O

2$ is shown below.

5 5

9 5

5

4 5 5 5 3 5 5 5 2 5 5 5 5 5 5 9 5 5 9 5 5

X Y

0

ra

n

sm

itta

n

c

e

:

& a % e n u m b e r : c m ?

;dentify the functional groups which cause the absorptions labelled XandY.

@sing this information draw the structures of the three possible structural isomers for A.

Gabel as A the structure which represents a pair of optical isomers.(/)

!b" ,raw the structures of the three 5&"*+67"8*al+enes with molecular formula C9H

5

,raw the structures of the three dibromoal+anes$ C9H5Br2$ formed when these three

al+enes react with bromine.

One of these dibromoal+anes has only three pea+s in its proton n.m.r. spectrum. ,educe

the integration ratio and the splitting patterns of these three pea+s.(10)

(T!"# 1/ %"&')

20. !a" 0he reaction of but>>ene with chlorine produces $2>dichlorobutane$ C4H

7Cl

2

!i" )i%en that chlorine e-ists as a mi-ture of two isotopes$39

Cl and38

Cl$ predict the

number of molecular ion pea+s and their m/z %alues in the mass spectrum of

C4H

7Cl

2

!ii" 0he mass spectrum of $2>dichlorobutane contains pea+s at m/z 1 88 and 86. ,raw

the structure of the fragment ion which produces the pea+ at m/z 1 88 and write an

equation showing its formation from the molecular ion.(/)

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!b" 0he reaction of but>2>ene with hydrogen chloride forms a racemic mi-ture of the

stereoisomers of 2>chlorobutane.

!i" Name the type of stereoisomerism shown by 2>chlorobutane and gi%e the meaning

of the term racemic mixture. State how separate samples of the stereoisomers could

be distinguished.

!ii" By considering the shape of the reacti%e intermediate in%ol%ed in the mechanism of

this reaction$ e-plain how a racemic mi-ture of the two stereoisomers of 2>

chlorobutane is formed.()

!c" 0he reaction of but>2>ene with chlorine produces 2$3>dichlorobutane$ C4H

7Cl

2

!i" State the number of pea+s$ their integration ratio and any splitting of pea+s in the

proton n.m.r. spectrum of 2$3>dichlorobutane.

!ii" Compound S$ an isomer of C4H

7Cl

2$ produces a proton n.m.r. spectrum which

consists only of a singlet$ a triplet and a quartet with an integration ratio of 3J3J2

respecti%ely.

Compound T$ also an isomer of C4H

7Cl

2$ produces a proton n.m.r. spectrum which

consists only of two singlets with an integration ratio of 3J

,raw the structures of S and of T.(/)

(T!"# 1$ %"&')

21. Butenedioic acid$ HOOCCH1CHCOOH$ occurs as two stereoisomers. One of the isomersreadily forms the acid anhydride C

4H

2O

3when warmed.

!a" ,raw the structures of the two isomers of butenedioic acid and name the type of

isomerism shown.

@se the structures of the two isomeric acids to suggest why only one of them readily

forms an acid anhydride when warmed. ,raw the structure of the acid anhydride formed.(/)

!b" ;dentify one electrophile which will react with butenedioic acid and outline a mechanism

for this reaction.

(4)

!c" &rite an equation for a reaction which occurs when butenedioic acid is treated with an

e-cess of aqueous sodium hydro-ide.(2)

!d" ,escribe and e-plain the appearance of the proton n.m.r. spectrum of butenedioic acid.(3)

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22. ropanoyl chloride can be used$ together with a catalyst$ in Step of the synthesis of >

phenylpropene from benzene %ia compounds Pand Qas shown below.

C O C H C H C H ! O H " C H C H C H C H C H22 3 3 3

S t e p S t e p 2 S t e p 3

P Q

!a" 0he mechanism of Step is an electrophilic substitution. &rite an equation to show the

formation of the electrophile from propanoyl chloride. Outline the mechanism of the

reaction of this electrophile with benzene in Step .()

!b" 0he mass spectrum of Pcontains a molecular ion pea+ at m/z1 34 and ma*or

fragmentation pea+s at m/z1 59 and 88. ;dentify the species responsible for the pea+ at

m/z1 59 and also that responsible for the pea+ at m/z1 88. &rite an equation for theformation$ from the molecular ion$ of the species responsible for the pea+ at m:z 1 59.

(4)

!c" NaBH4can be used in the reaction in Step 2. Name the mechanism in%ol%ed in this

reaction. Eolecules of Q show optical isomerism but the sample ofQformed in Step 2 is

optically inacti%e. State$ in terms of their structure$ why molecules of Qshow optical

isomerism. A-plain$ by reference to the mechanism$ why the sample of Qobtained in

Step 2 is not optically acti%e.()

!d" ;dentify a suitable reagent for the reaction in Step 3.

Name the type of stereoisomerism shown by the product of this reaction. State what isrequired in the structure of molecules to allow them to show this type of stereoisomerism.

(4)

(T!"# 20 %"&')

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23. !a" Aster X$ CH3CH

2COOCH

3$ can be produced by the reaction between propanoyl chloride

and methanol. Name Xand outline a mechanism for this reaction. Name the mechanism

in%ol%ed.(/)

!b" 0he proton n.m.r. spectrum of Xis shown below together with that of an isomeric

ester$Y. ,educe which of Spectrum and Spectrum 2 is that obtained fromX. @se T"5#+

1 on the ,ata Sheetand the integration data on the spectra to help you to e-plain your

deduction. Suggest a structure for Y.

5

5

6

6

7

7

8

8

9

9

4

4

3

3

2

2

5

5

: p p m

: p p m

S p e c t r u m ! i n c l u d i n g i n t e g r a t i o n d a t a "

S p e c t r u m 2! i n c l u d i n g i n t e g r a t i o n d a t a "

2

2

3

3

3

3

(4)

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24. 0he three compounds CH3CH

2CH

2CH

2OH$ !CH

3"3COH and CH

3CH

2CH

2CHO can be

distinguished by use of the following three reagents

. potassium dichromate!;" acidified with dilute sulphuric acid

2. 0ollensD reagent

3. ethanoic acid$ together with a small amount of concentrated sulphuric acid.

!a" ;dentify which of these three organic compounds would reduce acidified potassium

dichromate!;". )i%e the structures of the organic products formed. &rite a half>equation

for the reduction of dichromate!;" ions in acidic solution.(/)

!b" ;dentify which one of these three organic compounds would reduce 0ollensD reagent. )i%e

the structure of the organic product formed. &rite a half>equation for the reduction of

0ollensD reagent.(3)

!c" ;dentify which of these three organic compounds would react with ethanoic acid in the

presence of concentrated sulphuric acid. ;n each case$ gi%e the structure of the organic

product formed.(4)

!d" State the number of pea+s in the proton n.m.r. spectra of CH3CH

2CH

2CH

2OH and of

!CH3"3COH. !/nalysis of pea+ splitting is not required."

(2)

(T!"# 1 %"&')

2. !a" ,raw the structure of each of the three +etones which ha%e the molecular formula

C9H

5O. #or each compound gi%e the ratio of the areas under each pea+ in its low>

resolution proton n.m.r. spectrum.(/)

!b" ,raw the structure of each of the four aldehydes which also ha%e the molecular formula

C9H

5O. Gabel with the letter Xthe compound which has only two pea+s in its low>

resolution proton n.m.r. spectrum. Gabel with the letterYthe compound which has fi%e

pea+s with the ratios of the areas under each pea+ 3J3J2JJ in its low>resolution proton

n.m.r. spectrum. Gabel with the letter 9 the compound which shows optical isomerism.

()

!c" &hen carbonyl compounds react with HCN$ racemic mi-tures are often produced. Name

the type of mechanism in%ol%ed and e-plain what is meant by the term racemic mixture.

Choose any carbonyl compound which does *! form a racemic mi-ture when it reacts

with HCN and draw the structure of the product formed by the reaction of this carbonyl

compound with HCN.(4)

!d" A-plain why aldehydes react with 0ollenDs !or #ehlingDs" reagent but +etones do not.(3)

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2/. !a" ,escribe$ by gi%ing reagents and stating obser%ations$ how you could distinguish between

the compounds in the following pairs using a simple test>tube reaction for each pair.

!i"

C H C H

H H

C CH C H CO H C H Oa n d3 3

3 3

A B

!ii" C D

Ca n d

H C

H C

C H

C H

C

3 3

3 3

!iii"

C H C O O C H C H C H C O O Ha n d3 33 2

E F

(-)

!b" State how compounds E and F in part !a"!iii" abo%e could be distinguished by their infra>

red spectra$ without using the fingerprint region. A-plain howfingerprinting is used to

identify a compound.(3)

!c" Suggest the structure of the fragment responsible for the ma*or pea+ in the mass spectrum

of compound E and state its m/z %alue. &rite an equation showing the formation of this

fragment from the molecular ion.(4)

(T!"# 1 %"&')

2. @se the data gi%en on the bac+ of the eriodic 0able !0" to help you answer this question.

Compounds A to G are all isomers with the molecular formula CH

2O

2

!a" ;somer A$ CH

2O

2$ is a neutral compound and is formed by the reaction between

compounds X and Y in the presence of a small amount of concentrated sulphuric acid.

X and Y can both be formed from propanal by different redo- reactions.

X has an absorption in its infra>red spectrum at 895 cm?

.

,educe the structural formulae of A$ X and Y. )i%e suitable reagents$ in each case$ for

the formation of X and Y from propanal and state the role of concentrated sulphuric acidin the formation of A.()

!b" ;somers B$ C$ D and E all react with aqueous sodium carbonate to produce carbon

dio-ide.

,educe the structural formulae of the three isomers that contain an asymmetric carbon

atom.

0he fourth isomer has only three singlet pea+s in its proton n.m.r. spectrum. ,educe the

structural formula of this isomer and label it E.(4)

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!c" ;somer F$ CH

2O

2$ has the structural formula shown below$ on which some of the

protons ha%e been labelled.

3 2 2 2 3C H C H O C H C H C C H

Oa )

/ proton n.m.r. spectrum is obtained for F. @sing 0able at the bac+ of the eriodic

0able !0"$ predict a %alue of for the protons labelled a and also for those labelled .

State and account for the splitting patterns of the pea+s assigned to the protons a and .(/)

!d" ;somer G$ CH

2O

2$ contains si- carbon atoms in a ring. ;t has an absorption in its infra>

red spectrum at 3285 cm?

and shows only three different proton en%ironments in its

proton n.m.r. spectrum. ,educe a structural formula for G.(2)

(T!"# 1$ %"&')

2-. 0he con%ersion of compound A into compound B can be achie%ed in two steps as shown below.

C H C H

H B r

A B

C CXC H C HC H B r C H3 32 3

3 3S t e p S t e p 2

0he intermediate compound$ X: has an absorption at 95 cm?

in its infra>red spectrum.

!a" ;dentify compound X. A-plain your answer.(2)

!b" #or each step in this con%ersion$ gi%e the reagents and essential conditions required and

outline a mechanism.(11)

!c" Show how the number of pea+s in their proton n.m.r. spectra would enable you to

distinguish between compounds A and B.(2)

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2$. ;n the presence of /lCl3$ ethanoyl chloride reacts with the dial+ylbenzene A$ C

7H

5$ to form a

8*;#+compound B$ C5

H2

O. Compound Bis con%erted into C$ C5

H4

O$ on treatment with

NaBH4. Compound Dis produced when compound Cis warmed with concentrated H

2SO

4.

Compound Bhas a strong absorption band in the infra>red at 79 cm?

$ compound Chas a

broad absorption at 3345 cm?

and compound Dhas an absorption band close to 35 cm?

.

!a" Show how the information pro%ided in the question and the data in the 0able below can

be used to deduce structures for compounds A$ B$ Cand D.

A-plain the significance of the fact that B is obtained as a single compound.($)

!b" Name the types of reaction ta+ing place in each step and outline a mechanism for the

formation of compound Dfrom compound Cand concentrated sulphuric acid.()

!c" A-plain briefly why compound Ccan e-ist in stereoisomeric forms. (2)(T!"# 1- %"&')

30. roton n.m.r. spectroscopy can be used to distinguish between the following isomersJ

HOCH2CH

2OCH

3 HOCH

2OCH

2CH

3 CH

3OCH

2OCH

3

A B C

#or each of these isomers$ describe the appearance of the high>resolution proton n.m.r. spectrum

and account for any splitting patterns. /ssume that the OH protons are not coupled to any otherprotons.

(T!"# 1 %"&')

31. !a" 0he nitration of benzene is an e-ample of electrophilic substitution. 0he reagents for this

nitration are concentrated sulphuric acid and concentrated nitric acid in a J ratio and the

reaction is performed at 5 FC.

!i" A-plain what is meant by the term electrophile and the termsustitution#(2)

!ii" )i%e the name$ or formula$ of the electrophile in%ol%ed in this reaction and write an

equation or equations to show its formation from the reagents. &rite a mechanism

for the nitration of benzene.(/)

!iii" A-plain why the temperature of the reaction should not be allowed to rise abo%e

5FC.(1)

!b" Chlorobenzene is also prepared by electrophilic substitution. State the reagent!s" and

condition!s" required for this reaction to occur.

(3)

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!c" 0he structural formulae of compounds A: B: C and D: which are the four structural

isomers of molecular formula C4H

6Cl$ are gi%en below.

CH3CH

2CH

2CH

2Cl CH

3CH!Cl"CH

2CH

3 !CH

3"2CHCH

2Cl !CH

3"2C!Cl"CH

3

A B C D

Gow resolutionH NE< analysis of compounds A: B: Cand Dproduces two spectra

with 4 pea+s$ one spectrum with 3 pea+s and one spectrum with a single pea+.

!i" )i%e the name of compound D.(1)

!ii" ;dentify the compound (A: B: C or D) whose NE< spectrum shows a single pea+.

A-plain your reasoning.(2)

!iii" ;dentify the compound (A: B: C or D) whose NE< spectrum shows three pea+sand deduce the ratio of the areas under these pea+s. A-plain your reasoning.

(3)

!i%" &hen reflu-ed with an alcoholic solution of KOH$ compound B undergoes an

elimination reaction. 0wo structurally isomeric products are formed. ,raw the

graphical formulae of these two structural isomers.(2)

!%" ,raw the graphical formula for the product of the reaction between compound C

and NaOH!aq". )i%e an outline of the mechanism in%ol%ed in this reaction.(4)

(T!"# 24 %"&')

32. !a" 0he fragmentation of a molecular ion !E?dichloroethane shows pea+s at m:z %alues of 67$

55 and 52.(4)

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33. / molecular ion pea+ at mlz17 is present in the mass spectrum of each of three organic

compounds$ A: B and C. Aach compound has only two pea+s in its low>resolution proton n.m.r.

spectrum.

A is a hydrocarbon.

B and C are isomers and both ha%e a strong absorption near 855 cm?in their infra>red spectra.

/ table of infra>red absorption data is pro%ided below.

!a" #or each compound$ gi%e the molecular formula and draw a possible structure. ,educe

the ratio of the pea+ areas in the low>resolution proton n.m.r. spectrum of each

compound.($)

!b" ,escribe how you could distinguish between B and C using a chemical test. How could B

or Cbe identified using its infra>red spectrum=()

!c" D and E are isomers of B and C.

D has infra>red absorptions at 3355 cm?

and also at 95 cm?

.

E has an infra>red absorption at 3355 cm?

but none near 95 cm?

.

,raw and label one possible structure each for D and E. A-plain your answer.(4)

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34. !a" A-plain what is meant by the fingerprint region of an infra>red spectrum and describe

how it is used to confirm the identity of organic molecules.(4)

!b" Aach of three isomeric esters$ Q: Rand S$ of molecular formula C9H

5O

2has a branched

structure.

Qhas only two pea+s in its low resolution proton n.m.r. spectrum$ but Rand Seach ha%e

three pea+s.

Hydrolysis of Rin acid conditions forms compounds Tand U. 0he low>resolution proton

n.m.r. spectrum of Thas three pea+s and that of Uhas two pea+s. ;nfra>red spectra of T

and Uare shown below.

,raw structures of the compounds Q: R:S$ Tand Uand e-plain how the n.m.r. and i.r.

data support your conclusions. / table of infra>red absorption data is pro%ided below.

5 5

6 5

7 5

8 5

5

9 5

4 5

3 5

2 5

5

5

0

ra

n

sm

itta

n

c

e

:

4 5 5 5 3 5 5 3 2 5 5 2 7 5 5 2 4 5 5 2 5 5 5 7 5 5 5 5 4 5 5 2 5 5 5 5 5 7 5 5 9 5

& a % e n u m b e r : c m ?

T

5 5

6 5

7 5

8 5

5

9 5

4 5

3 5

2 5

5

5

0

ra

n

sm

itta

n

c

e

:

4 5 5 5 3 5 5 3 2 5 5 2 7 5 5 2 4 5 5 2 5 5 5 7 5 5 5 5 4 5 5 2 5 5 5 5 5 7 5 5 9 5

& a % e n u m b e r : c m ?

U(11)

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3. Simple organic compounds$ including structural isomers$ can be distinguished from each other

by chemical tests$ or by spectroscopic methods$ or by a combination of both. 0his question

concerns the four compounds whose structural formulae are shown below.

CH3!CH

2"2CHO !CH

3"2CHCHO CH

3COC

2H

9CH

3COOC

2H

9

A B C D

!a" ,raw graphical formulae for A$ B$ C and D$ clearly indicating which is which. )i%e the

names of A$ B$ Cand D.(-)

!b" Compound Dcan be made by a reaction called esterification. State the names of !,

compounds needed for the reaction and gi%e a condition used in the reaction.(3)

!c" )i%e the name and draw the graphical formula of an isomer of compound Dthat is *!an

ester.(2)

!d" ,escribe *+chemical test that would distinguish between Band C$ and state what you

would obser%e in each case.(3)

!e" 0heH NE< spectra of A$ B$ Cand Dcan be used to distinguish between some of the

structures by considering the numbers of pea+s and the ratios of the areas under them.

0he following table shows some results of aH NE< in%estigation into A$ B$ Cand D.

Aach of the four spectra is referred to by a number.

S+!&% N%5+& < +"' R"!8 < "&+" *6+& !+ +"'

3 J J

2 4 3 J 2 J 2 J

3 3 3 J 2 J 3

4 3 3 J 2 J 3

!i" &hich compound !A$ B$ Cor D" corresponds to spectrum = )i%e a reason foryour choice.

(2)

!ii" &hich compound !A$ B$ Cor D" corresponds to spectrum 2= )i%e a reason for

your choice.(2)

!iii" A-plain why spectrum 3 and spectrum 4 ha%e the same number of pea+s and the

same ratio of areas under them.(1)