Science Bowl Organic Chemistry Notes

7/29/2019 Science Bowl Organic Chemistry Notes

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Aliphatic Functional Groups to Know and Love


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Common Aromatic Compound Names


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Nomenclature Roots

Meth- (Me)/Form- : -CH3

Eth- (Et)/Acet- : -CH2 CH3

Prop- (Pr) : -CH2 CH2 CH3

But- (Bu) : -CH2 CH2 CH2 CH3

Pent- : -CH2 CH2 CH2 CH2 CH3

Hex- : -CH2 CH2 CH2 CH2 CH2 CH3

Hep- : -CH2 CH2 CH2 CH2 CH2 CH2 CH3

Oct- : -CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3

Non- : -CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3

Dec- : -CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3

Undec- : -CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3

Dodec- : -CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH2 CH3

Tridec- : -C13H27

Tetradec- : -C14H29

Pentadec- : -C15H31

Hexadec- : -C16H33

Heptadec- : -C17H35

Octadec- : -C18H37

Nonadec- : -C19H39

Eicos- : -C20H41

Triacont- : -C30H61

Tetracont- : -C40H81

Pentacont- : -C50H101

Decacont- : -C100H201


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Structural Formulas

Molecular FormulaA count of each atom type. Molecular formulas can represent

multiple compounds. Ex: C2H4O

Kekule StructuresStructures that show the position of every atom and bond.

Condensed StructuresStructures that group functional groups together.

Alternatively:

What about larger compounds?

Line structuresStructures where carbons are represented by ends and corners

unless otherwise indicated. Hydrogens bonded to carbons are implied. All otheratoms are shown.


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Alkanes (C-C)

Saturated hydrocarbonsEach carbon has the maximum number of hydrogens

present. Formula:

Unsaturated hydrocarbon: At least one carbon has fewer than the maximumnumber of hydrogens allowed.

Properties of Alkanes

Intermolecular Forces:

Polarity:

Boiling Point:

Solubility:

Acidity/Basicity:

Hybridization and VSEPR Geometry:

Valence Bonds:


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IsomersDifferent molecules with the same molecular formula.

Constitutional IsomersIsomers that differ in connectivity.

C4H10:

C5H12:

Degree of Branching

Primary carbons (1o) will have ____ bonds to a carbon.

Secondary carbons (2o) will have ____ bonds to carbons.

Tertiary carbons (3o) will have ____ bonds to carbons.

Quaternary carbons (4o) will have ____ bonds to carbons. These are rarely reactive.

In the case of double and triple bonds, each pi bond counts as one bond.

Functional groups will adopt the degree of branching of the carbon they are bondedto.

In the molecule below, circle the 2o carbon(s). Box the 3o carbon(s). Draw anarrow to the 4ocarbon(s). Dont disturb the 1o carbon(s).


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Alkane Nomenclature

1. Identify the largest continuous chain of carbons. This is called the parentchain.

2. If there are two series of carbon of the same length, rings take priority overchains.

3. Identify the substituents and number the carbons on the parent chain so thatthe substituents have the lowest possible numbering.


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If the substituent is a carbon chain, name it as a parent chain and replace

ane withyl.

4. List substituents alphabetically. Ignore prefixes.

5.

Replicated substituents are grouped together using di-, tri-, tetra-, penta-,hexa-, hepta-, etc. The prefix is not used to alphabetize substituents.


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6. Common substituents:OH = hydroxyl NH2 = amino CN = cyano

Cl, Br, F = chloro, bromo, fluoro NO2 = nitro

Name the following compound:


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Cycloalkanes

Cycloalkanes have the same properties as alkanes. The formula of a basic

cycloalkane is:

Angle strainThe energetic resistance of bond angles to deviate from theirVSEPR angles

Cyclopropane and Cyclobutane:

High angle strain = unstable

sp3-hybridized carbons prefer _______ bond angles

Planar or puckered (cyclobutane only) conformations (3-D geometries)

Cyclohexane:

The angles of a regular hexagon are _______; therefore, cyclohexane will prefer to

adopt a 3-D shape to minimize angle strain.

________ conformations are the _______ stable conformations of cyclohexane.Cyclohexane can have ___ two possible conformers of this type that can

interconvert between each other.

Axial sites - __________ to the cyclic plane, alternate up and down. Substituents inthe axial position make the cyclohexane ______ stable.

Equatorial sites - __________ to the cyclic plane, alternate up and down.Substituents in the equatorial position make the cyclohexane ______ stable.


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Label the sites below as axial or equatorial.

Why are conformers with substituents in the equatorial position more stable?

Steric hindranceWhen the size of a large substituent competes for space with an

adjacent group. This can lead to limited chemical reactivity and instability

t-butylcyclohexane

Substituent in axial position Substituent in equatorial position


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Dash ( )indicates atoms going ________ or ________ the plane of paper

Wedge ( )indicates atoms going ________ or ____________ the plane of

paper

Two substituents are ______ to each other when they are going in the same

directions. They are ______ to each other when they are going in differentdirections.

Draw planar representations of the two molecules above.

Out of all cycloalkanes, cyclohexane will experience the least strain in its bonds;smaller cycloalkanes will suffer from angle strain, and larger cycloalkanes will

experience strain from steric hindrance of its substituents.


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Bicyclic moleculesMolecules with two rings that share a side

Spiro moleculesMolecules with two rings that share an atom

Bridged moleculesMolecules with three rings that share two atoms with each

other

Heterocyclic moleculesMolecules with a ring in which a carbon has been

replaced with any non-carbon atom.

Classify the following molecules:


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Alcohols and Alkyl Halides (R-CH2-OH)/(R-X)

Properties of alcohols/alkyl halides:

Intermolecular Forces

Polarity

Boiling Point

Solubility

Acidity/Basicity

Hybridization

Nomenclature

For alcohols, list the group as a substituent or use the alcohol as part of the parent

name by replacing the laste withol.

For alkyl halides without hydroxyl groups, list the group as a substituent or replace

theane of the parent chain withyl, then replace theine of the halogen with

ide.


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A special note on alcohols: _____ alcohols can oxidize to aldehydes, while _____

alcohols can oxidize to ketones.

Random fact: heating an alcohol in the presence of a strong acid will produce analkene. Such types of reactions where alkenes are formed from taking out two

substituents on adjacent carbons are termed ________________ reactions. For

example:


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Stereochemistry

StereoisomersCompounds with the same formula, constitution, and functional

groups in the same place but have a different orientation in space

A molecule is termed __________when it isnt superimposable on its mirror

image. The center of stereochemistry is typically ______ -hybridized. Typically,

but not always, a molecule will be chiral if a carbon has _____ different

substituents bonded to it

EnantiomersTwo molecules that are mirror images of each other but are not

super-imposable

In an achiral environment, enantiomers will behave identically and have the same

physical properties except for their rotation of ____________________________.

Racemic mixture: a ________ mixture of two enantiomers. These will not rotate

light.

Molecules that rotate light clockwise are termed dextrorotatory and are indicated

by a (+) in front of their name.

Molecules that rotate it counterclockwise are termed levorotatory and are indicated

by a (-) in front of their name.


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Enantiomers can also be named with the R/S or E/Z systems. Names are

determined based on the molecular masses of substituents and their spatial

arrangement relative to each other.

Finally, they can be named with the L/D system, where the name of the compound

is determined based on whether the compound forms from the L or D enantiomer

of glyceraldehyde.

Diastereomerstwo stereoisomers that are not mirror images to each other. These

have at least ____ chiral centers


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Alkenes (C=C)

Formula:

Properties

Hybridization:

Valence Bonds:

All other properties are similar to those of ________________.

Nomenclature

Name the alkene like you would an alkyl chain, but drop theane and addene.

The parent chain must contain the double bond. Be sure to indicate which number

carbon starts the double bond.

Vinyl alkenes, or terminal alkenes, have a double bound at the end of a chain. Allyl

alkenes have a double bond at a 2-carbon. Note: alkenes dont necessarily have to

be either vinyl or allyl.

Indicate which of the above alkenes are vinyl or allyl.


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In alkanes, carbon-carbon sigma bonds can rotate freely. However, alkenes cant

rotate due to the necessity of massive energy to break pi bonds. This introduces the

possibility of ________________ isomers.

When the two heaviest substituents on opposite carbons in a double bond are on

the same side of the double bond, _________ or ______ is written before their

names. If they are on opposite sides and are diagonal to each other, _________ or

______ is written before their names. In general, the _______ isomer of an alkene

will be more stable than the _______ isomer.

Fun fact: alkenes are popular compounds for undergoing ____________________

reactions, where the double bond is broken by adding a substituent to each sp2-

hybridized carbon of the said pi bond. Three of many types of these reactions are

given below:


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Formula-

Properties

Acidity/Basicity

Hybridization

Valence Bonds

All other properties are similar to those of _______________________________.

Nomenclature

Name the alkyne like you would an alkene, except replaceene withyne.

An alkyne that has the formula RC2H is classified as _______________ alkynes.All others are _________________ alkynes.


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Acidity of terminal alkynes

Protons on terminal alkynes are more easily extracted than those on alkenes and

alkanes because the triple bond has _______________ character.


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Dienes

A diene is an alkene with ______ carbon-carbon double bonds.

____________ dienea diene with double bonds that act independently of each

other. The double bonds are always at least ______ carbons away from each other.

____________ dienea diene with double bonds _______ carbon away from eachother. The pi electrons delocalize*, making the diene very _____________.

____________ dienea diene where a carbon atom has _____ double bonds. The

pi bonds are perpendicular to each other and require a lot of energy, making the

diene very _____________.

*In organic chemistry, electron delocalization will always lead to compound and

ion stability. These electron delocalizations always occur within the pi orbitals and

can occur in compounds with adjacent double bonds or with a series of adjacent pi

bonds and electric charge, radical electrons, or lone pairs. These structures will

always have multiple resonance structures. In other words, compounds that show

resonance have electron delocalization, which stabilizes them.


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Diels-Alder Reaction

A ______________ diene will react with an______________, in this case termed a

______________, to form a ___________________.

Cycloalkenes

Cycloalkenes are carbon rings that include one double bond between two carbons

in the ring. Their general formula is _____________________. These cycloalkenes

dont undergo conjugative delocalization of pi electrons and thus dont exhibit

resonance (such structures are discussed in the next section.


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Aromaticity

Compounds are said to be _______________ when it contains a conjugated ring of

delocalized pi electrons that increase the stability of the compound. (It will thus

show resonance)

A special note on benzene

After experimentation, August Kekule determined the following in relation to

benzene:

1. Benzenes molecular formula is C6H62. All the hydrogens on benzene are equivalent3. The octet rule requires that there be four bonds to each carbon

Kekule then hypothesized the following structures for benzene:

However, a flaw was soon discovered in the structure. Kekules structure suggests

that the following compounds would have different properties:


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The structure implies that a single bond connects the carbons of two substituents in

one isomer and a double bond connects the carbons in the second.

However, no such cases of isomerism were known, and none could be found.

Kekule therefore proposed that two isomers could exist but interconverted too

rapidly to be noticed:

We know that this isnt the case. Experiments show that all of the carbon-carbon

bonds in the ring are energetically equivalent and have a bond length of 140 pm,

exactly halfway between the sp2-sp2 double bond length of 134 pm and the sp2-sp2

single bond length of 146 pm.

The two structures correctly show the arrangement of atoms, but they differ in the

placement of electrons. Thus, they are resonance structures, and neither shows the

correct bonding of benzene by itself. We therefore know that the hybrid structure

of benzene has the following appearance:


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The bond angles in benzene are _________, the angles of a regular hexagon. Since

________-hybridized atoms prefer these angles, benzene will remain planar

instead of twisting into a 3-D shape like cyclohexane. Furthermore, the conjugative

delocalization of pi electrons enhances benzenes stability to such a degree that the

bonds within the ring all act together as one functional group instead of six

separate bonds.

A Demonstration of Aromatic Stability

Cyclohexanol Deprotonation -

Phenol Deprotonation -


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Nomenclature

In monosubstituted benzene derivatives, if using benzene for the parent chain, treat

substituents like you would with an alkane.

If using benzene as a substituent, name it a phenyl (Ph) group.

If using benzene attached to one carbon, name it a benzyl (Bz) group.


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For disubstituted benzene derivatives, use ortho- or o- if the substituents are

next to each other, meta- or m- if the substituents are separated by a hydrogen,

and para or p- if the substituents are on opposite ends of the ring.

For trisubstituted derivatives and above, use the numbering system.


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Refer to the table of benzene derivatives at the beginning of this packet for more

common benzene derivatives.

Friedel-Crafts Alkylation/AcylationAlkylation:

Acylation:


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Ethers (R-O-R)

Properties of Ethers


Polarity:

Boiling Point:

Solubility:

Acidity/Basicity:


Valence Bonds:


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Compound Structural

Formula

Dipole

Moment (D)

Boiling Point

(oC)

Solubility in

H2O(g/100 mL)

Dimethyl ether CH3OCH3 1.3 -24 0.071

Propane CH3CH2CH3 0 -42 0.004

Ethanol CH3CH2OH 1.69 78 Miscible

Nomenclature

If naming the ether as a substituent, take the smaller chain attached to the oxygen,

replaceane withoxy, and add the name of the parent chain after it.

If naming the ether as a functional group, replace theane of the side chains with

yl, write them alphabetically, and add ether. If both side chains are the same,

write di and then the side chain once before writing ether.

Cyclic Ethers and Epoxides

The carbons attached to the ether oxygen can be bonded to other chains that form a

ring. These ethers are called cyclic ethers. Example: Tetrahydrofuran (THF)


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Epoxides are a special type of cyclic ethers where the carbons bonded to the ether

oxygen are also bonded to each other. Epoxides tend to be ____________ because

of ____________________. Example: oxirane, 1,2-epoxycyclohexane

Aldehydes and Ketones (RH=O)/(RR=O)

Properties of Aldehydes and Ketones


Polarity:

Boiling Point:

Solubility:

Acidity/Basicity:


Valence Bonds:


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Nomenclature

For aldehydes, name the compound like you would an alkyl chain and replace the

ane withal.

For ketones, name the compound like you would an alkyl chain and replace the

ane withone.

If a compound contains both an aldehyde group and a ketone group, the aldehyde

takes priority. Use oxo- to name the ketone group substituent.* Be sure to mark

the # carbon the ketone is on.

*Something useful to know: any C=O group is called a ________________ group.


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Aldehydes and ketones will oxidize to ____________________ and ___________

respectively. They will reduce to _________________________ and

________________________ respectively.


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Carboxylic Acids and Esters (RCOOH)/(RCOOR)

Properties of Acids and Esters


Polarity:

Boiling Point:

Solubility:

Acidity/Basicity:

Nomenclature

For carboxylic acids, name the acid like you would an alkyl chain, then drop the

ane and add -oic acid.

For esters, list the chain bonded to the oxygen as a substituent, then name the

parent like you would an alkyl chain. Replace thee on the end of the parent chain

withoate.


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Carboxylic acids and esters will reduce to ______________ and _______________

respectively.

Fischer Esterification

Perhaps the most common way to prepare esters is through the Fisher

Esterification, which involves an equilibrium reaction between a carboxylic acid

and an alcohol. Note: the acid will retain both of its oxygens and lose only the


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proton bonded to the second oxygen, while the alcohol will lose its hydroxyl

group.

Saponification- KNOW THIS

Although soap has many ingredients that contribute to its properties, the main

active molecule involves an anion with a polar carboxylate head and a nonpolarfatty acid tail bonded to a sodium or potassium cation. The structure of the sodium

salt is displayed below:


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Common carboxylate salts:


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When in water, these sodium/potassium salts dissociate. The nonpolar fatty acid

tails of the carboxylates are hydrophobic and thus prefer to bond intermolecularly

with other fatty acids, forming a sphere coated with polar heads and filled with

fatty acid tails. These spheres are termed micelles.

We use soap to wash our skin because nonpolar compounds on our skin wontbond to the water and fall off due to strong intermolecular forces. When we scrub

soap on our skin, the micelles break, and the fatty acid tails bond to the nonpolar

substances. The micelles re-form with the unwanted residue trapped inside, and the

polar heads hydrogen-bond with water to carry the substances away.

Whether sodium or potassium is used to make the soap does have an effect on the

product. In general, a sodium salt will produce solid soap, which will be treatedwith further chemicals to form a bar. A potassium soap will typically be liquid,

which will be treated to form a soap gel.

Fatty acids are normally found in the form of triglycerides instead of monomers. In

the laboratory, saponification typically occurs by reacting a vegetable oil, a reliable

source of triglycerides, with sodium hydroxide in the presence of water, ethanol,

and heat. Sodium hydroxide by itself is a caustic solid and must be dissolved with

water to react. In addition, triglycerides do not dissolve in water, limiting the

saponification reaction to the surface, so ethanol is added to dissolve the

triglyceride into the aqueous solution. Finally, saponification is an endothermic

reaction and requires an external source of heat for the reaction to occur.

The basic chemical reaction for in-lab sodium saponification is displayed below:


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Amines

Properties of Amines


Polarity:

Boiling Point:

Solubility:

Acidity/Basicity:



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Nomenclature

There are two ways to name amines where the nitrogen is bonded to only one

carbon (primary amines): in the alkanamine system, take the parent chain, drop the

laste, and addamine. In the alkylamine system, replace theane of the parentchain withyl and add amine to the end. Remember to denote the location of the

amine with numbering in both cases.

Note: amines bonded to phenyl rings are called anilines.

Other amines are named as N-substituted derivatives of primary amines. Theparent chain is taken to be the one with the longest carbon chain. Rings, however,

take precedence over chains.

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Science Bowl Organic Chemistry Notes