Organic Chemistry
Lesson # 2: Functional Groups
Functional Groups
 A functional group is an attachment on a hydrocarbon
which completely changes its physical and chemical
properties, and determines a new homologous series.
 A functional group can be as simple as a single atom or
a much more complex structure.
 Note that double or triple bonds are NOT functional
groups.
 Functional groups usually contain oxygen, nitrogen, or
halogens, and can be single, double, or triply bonded to
carbon.
1. The Hydroxyls
 There are two types of hydroxyl groups: the alcohols
and the ethers.
 These groups contain an - O - group in the place of a
hydrogen.
Alcohols
 Methanol is highly toxic, and drinking even small
quantities can lead to blindness and death.
 Ethanol is the most important alcohol economically.
Apart from its uses as an industrial solvent, it can be
used as a fuel. Many gasolines contain up to 15%
ethanol and in South America, up to 50%.
 2-Propanol is also known as rubbing alcohol.
Drawing Alcohols
a) ethanol
b) 2-butanol
c) 2-methyl-3-hexanol
Naming Alcohols
CH2
H3C
OH
OH
CH2
CH2
H3C
CH3
CH
CH2
HO
CH3
CH2
CH
H3C
CH
CH3
Ethers
 Ethers are compounds in which two alkyl groups are
joined to oxygen.
 Ethers are highly flammable, polar solvents.
 Ethoxyethane has a boiling point of 34°C and its
vapours are extremely flammable. If it is poured into
one corner of a room with an open flame in the
opposite corner, it could ignite. It was actually used as
an anaesthetic for dentistry when laughing gas was
proved unreliable.
 Note that when name ethers, the shortest hydrocarbon
alkyl group is named first, no matter to which side of
oxygen it lies.
Drawing Ethers
a) Methoxybutane
b) Ethoxypentane
c) Propoxypropane
Naming Ethers
H3C
CH2
CH3
O
CH2
H3C
CH2
O
CH2
CH2
CH3
2. The Carbonyls
 There are two types of carbonyl groups: the aldehydes
and the ketones.
Aldehydes
 Aldehydes are compounds in which the carbonyl
group is attached to a terminal (end) carbon.
 Methanal is used as a preservative for biological
specimens, however it is thought to be carcinogenic.
Its old name is formaldehyde.
 Aldehydes with higher molecular mass tend to have
pleasant and flowery odour, and are found in essential
oils of plants.
Ketones
 Ketones are compounds in which the carbonyl
is on a central or non-terminal carbon (in the
middle).
 Ketones are used as industrial solvents.
Propanone (old name – acetone) is a widely
used household solvent.
Drawing Aldehydes & Ketones
 a) Propanal
b) 3-hexanone
 c) Propanone
d) 2-methyl butanal
 e) Pentanal
f) 3,4-dimethyl-2-heptanone
Naming Aldehydes & Ketones
CH3
O
C
H3C
H3C
HC
CH3
CH2
CH3
O
CH
C
CH3
CH
HC
CH3
CH
3
CH2
H3C
CH2
C
H
O
O
H
C
H
3. The Carboxyls
 There are two types of carboxyl groups: the carboxylic
acids and the esters.
Carboxylic Acids
 Carboxylic acids are a combination of
aldehyde and alcohol.
 Carboxylic acids are weak acids, which
means they do not completely dissolve in
water.
 Another name for ethanoic acid is acetic
acid, which is in vinegar.
Drawing Carboxylic Acids
 a) Ethanoic Acid
 c) 3-methyl pentanoic acid
b) Butanoic Acid
Naming Carboxylic Acids
O
C
HO
CH2
O
H3C
CH3
H3C
H3C
CH C
H3C
CH2
CH2
CH2
CH2
CH2
O
C
OH
C
CH3
OH
Esters
 Esters are sweet smelling and many esters occurred
naturally in fruit and flowers.
 They are widely used as flavour and aroma additives
in the food industry.
 To name, the carbon chain attached directly to the
single bond oxygen is named as an alkyl group, and
the other chain becomes the ending name.
Drawing Esters
a) methyl butanoate
c) pentyl propanoate
b) octyl ethanoate
Naming Esters
H
CH2
H3C
O
CH3
CH2
C
CH2
C
O
CH2
O
O
H2C
CH3
O
CH2
H3C
CH2
CH2
O
CH2
O
C
C
CH3
H3C
O
CH2
CH3
4. The Nitrogen Compounds
 There are two functional groups involving nitrogen: the
amines and the amides.
Amines
 Amines are sometimes called organic bases.
 The lone pair of electrons on the nitrogen is
responsible for most of the properties.
 The word “amino” starts the hydrocarbon naming,
instead of using a suffix.
Drawing Amines
 a) 2-aminobutane
 c) 3-methyl 2-aminopropane
b) aminoethane
Naming Amines
CH3
HC
H3C
CH2
H2N
CH2
CH
H2N
CH3
CH2
CH2
H3C
CH3
NH2
Amides
 Amides are important because they are the linkages
contained in proteins and some synthetic polymers.
 To name, the carbon chain attached directly to the
single bond nitrogen is named as an alkyl group, and
the other chain becomes the ending name, similar to
esters.
Drawing Amides
 a) propyl ethanamide
c) pentyl methanamide
 b) methyl butanamide
d) butyl ethanamide
Naming Amides
O
CH2
H3C
C
CH2
CH2
N
CH3
CH2
O
H
C
N
CH3
H
H
H
N
O
CH2
CH2
CH3
C
CH2
H2C
CH3
NH
C
O
CH3
CH3
CH2
Functional Group & Boiling
Point/Solubility
Functional Group
Type of Bonds
Hydrogen Bonds
Alcohols
Double Bonds to O
Single Bonds to O or N
O – H hydrogen bonds
Ethers
O – C polar bonds
Aldehydes
O = C polar bonds
Ketones
O = C polar bonds
Carboxylic Acids
O – H hydrogen bonds
Esters
O = C polar bonds
O = C polar bonds
Amines
N – H hydrogen bonds
Amides
N – H hydrogen bonds
O – C polar bonds
N – C polar bonds
O = C polar bonds
N – C polar bonds
Polarity & Boiling Points and Solubility
 The functional groups with hydrogen bonds have the highest boiling
points and can dissolve the most substances, and hydrogen bonding is
the strongest intermolecular force.
 *intermolecular means “between molecules”*
 The functional groups with polar bonds have slightly lower boiling points
and have a limited ability to dissolve substances, both polar and nonpolar.
 The hydrocarbons have by far the lowest boiling points, and can only
dissolve non-polar substances, as they do not contain any polar bonds.
 “polar” means they do not share electrons equally – stronger bonds
 “non-polar” means they share electrons equally – weaker bonds