Download Pop-Quiz Sit down quietly and draw the following structures.

Pop-Quiz
Sit down quietly and draw the
following structures.
Pop-Quiz
Draw the following structures:
Heptan-2-ol
Cyclopropanal
1-propoxypentane
Heptan-3-one
2,4,6-trichloroheltanal
Nomeclature:
Carboxylic acids and Esters
Structure of carboxylic acids and their
derivatives
• The functional group present in a carboxylic acid is a
combination of a carbonyl group and a hydroxyl group;
however, the resulting carboxyl group ( -COOH) possesses
properties that are unlike those present in aldehydes/ketones
and alcohols.
carbonyl group
hydroxyl group
carboxyl group
Structure of carboxylic acids and their
derivatives
• Carboxylic acids have the following general formula:
• Some simple carboxylic acids:
formic acid
IUPAC: methanoic acid
acetic acid
IUPAC: ethanoic acid
IUPAC: benzoic acid
• Since carbon can have only four bonds, there are no cyclic
carboxylic acids (i.e. the carboxyl group cannot form part of a
carbon ring)
IUPAC nomenclature for carboxylic
acids
• For monocarboxylic acids (one –COOH group):
– Select the longest, continuous carbon chain that involves the
carboxyl group. This is the parent chain and the –COOH carbon
is designated as C-1.
– Name the parent chain by dropping the “e” from the
corresponding alkane name and changing to “oic acid”
– Indicate the identity and location of substituents on the parent
chain at the front of the carboxylic acid’s name
Benzoic acid
Butanoic acid
3,3-Dibromobutanoic acid
2-Methylpropanoic acid
3,5-Dichlorobenzoic acid
IUPAC nomenclature for carboxylic
acids
• Dicarboxylic acids:
– For these compounds, both ends of a chain will end with a
–COOH group. The parent chain is the one that involves
both –COOH groups.
– The parent chain is named as an alkane and the term
“dioic acid” is added afterwards to indicate the diacid
structure.
Butanedioic acid
(Succinic acid)
Bromobutanedioic acid
Bromosuccinic acid)
Common names for carboxylic acids
Common names for dicarboxylic acids
Common names for carboxylic acids
• For common-name carboxylic acids and diacids, substituents
are often numbered using a Greek system:
Greek letter




carbon number
5
4
3
2
1
• So the following molecule is called 2-Methylpropanoic acid.
Polyfunctional carboxylic acids
• Carboxylic acids that contain other functional
groups besides the –COOH group are called
polyfunctional carboxylic acids. Some
examples are shown below:
an unsaturated acid
a hydroxy acid
a keto acid
Task 2
Give IUPAC names for the following:
A. CH3COOH
CH3
|
B. CH3CHCOOH
12
Solution 2
A. CH3COOH
ethanoic acid
CH3
|
B. CH3CHCOOH
2-methylpropanoic acid;
13
Physical properties of carboxylic
acids
• Carboxylic acids are the most polar functional
group we have seen so far. The presence of
the carbonyl group next to the OH causes the
O-H bond to be even more polar.


alcohols




carboxylic acids
Physical properties of carboxylic
acids
• Because of the very polar –COOH group, carboxylic acids
exhibit strong intermolecular attractions.
• As expected, carboxylic acids of a given number of carbon
atoms have higher boiling points than alcohols.
• Carboxylic acids also tend to dimerize, producing molecules
that are twice as heavy which have enhanced London forces
(and thus still higher boiling points).
two H-bonds between two molecules
"dimer"
Comparing Boiling Points
Physical properties of carboxylic
acids
• In terms of water-solubility,
because of H-bonding, carboxylic
acids dissolve well in water (up to
4-carbon chains).
• Beyond 4 carbons, water-solubility
drops off rapidly.
Structure of esters
• Esters are carboxylic acid derivatives having an
alkoxy group instead of a hydroxyl group.
carboxylic acid
ester
Nomenclature for esters
• Thinking of an ester in terms of an “alcohol portion” and a “carboxylic acid
portion” is important for naming esters using the IUPAC system:
1. The name for the alcohol portion comes first: name the alkyl part of
the alcohol (e.g., for the ester shown below, the first part of the
ester’s name is methyl (alcohol part comes from methanol). Present
the alkyl name separate from the remainder of the ester name.
2. The carboxylic acid portion is named as if it were deprotonated,
changing the “-ic acid” part of that name to “-ate”
Methyl propanoate
derives from derives from
propanoic acid
methanol
This part would be called “propanoate”
Nomenclature for esters
• Some other examples:
Ethyl butanoate



Ethyl 2-methylbutanoate
Ethyl -methylbutyrate
2-Methylpropyl butanoate
Isobutyl butanoate
2-Butyl butanoate
Sec-Butyl butanoate
Selected common esters
• Flavor/fragrance agents
Selected common esters
• Pheromones:
alarm pheromone for honeybee
sexual attractant for canines
• Medications:
benzocaine
Aspirin
Selected common esters
• Synthesis of Aspirin
H+
H2O
heat
salicylic acid
Aspirin
acetic acid
• Synthesis of oil of wintergreen:
H+
Methanol
H2O
heat
Aspirin
salicylic acid
Task 2
Give the IUPAC name of the following
compound, which is responsible for the flavor
and odor of pears.
O

CH3 — C—O —CH2CH2CH3
24
Solution 2
O

propyl
CH3 — C—O —CH2CH2CH3
propyl ethanoate (IUPAC)
25
Isomerism in carboxylic acids and
esters
• Recall that structural isomers are molecules that share the same formula
but differ in their atom-to-atom connectivities.
• Carboxylic acids and esters that have a given number of carbon atoms
form another example of functional group isomers:
functional
group
isomers
Butanoic acid
C4H8O2
Methyl propanoate
Physical properties of esters
• Because they don’t possess OH groups, esters cannot form Hbonds with other ester molecules. As a result, esters have
lower boiling points than carboxylic acids and alcohols that
have approximately the same molar mass.
• Water molecules can H-bond to esters, at the oxygen atoms.
This makes low molecule weight esters water-soluble.
Task 3
Draw the structure of the following compounds:
A. 3-bromobutanoic acid
B. Ethyl propionoate
28
Solution 3
A. 3-bromobutanoic acid
Br
|
CH3CHCH2COOH
B. Ethyl propionoate
O

CH3 CH2 COCH2CH3 CH3CH2COOCH2CH3
29