Download Unit C Lesson 6 Carboxylic Acids And Esters

Carboxylic Acids

Carboxylic acids are weak acids that contain the carboxyl group (-COOH)
Carboxyl group 

C=O
|
OH
The hydrogen attached to the carboxyl group is released when these molecules ionize
in water.
R-COOH(aq) + H2O(l)

R-COO-(aq) + H3O+(aq)
Naming and Drawing Carboxylic Acids:
 Identify the root
Locate the longest chain that includes the carboxyl group. Name the
parent alkane.
 Identify the suffix
Drop the –e at the end of the name of the parent alkane and replace it with
–oic acid.
 Identify the prefix
Name and number any alkyl side groups on the main chain. The carbon
atom of the carboxyl group is always number one.

EX. Name the following compound

EX. Name the following compound

EX. Name the following compound

EX. Name the following compound

EX. Draw the structure of butanoic acid

EX. Draw the structure of 4-bromo-2-methylpentanoic acid

EX. Draw the structure of 2,3-difluoropropanoic acid

EX. Draw the structure of 3-phenylbutanoic acid
Physical Properties of Carboxylic Acids

The carboxyl group is very polar, allowing the molecules to form hydrogen bonds
with one another. The result is much higher boiling points than for other
hydrocarbons and derivatives with the same number of carbon atoms.
Compound
butane
butan-1-ol
butanoic acid
Boiling Point (oC)
- 0.5
117.2
165.5

Short-chain molecules are liquids at standard temperature while longer-chain
molecules are waxy solids.

The polarity of the carboxyl group makes the short-chain (1 to 4 C atoms) molecules
to be very soluble in water.

As the hydrocarbon chain becomes longer, the non-polar characteristics of the chain
cause the larger carboxylic acids to be less soluble in water.
 Molecules of 5 to 9 C atoms are less soluble
 Chains of 10+ C atoms are insoluble in water

Carboxylic acids are weak acids  they turn litmus paper red and conduct electricity.
Esters

An ester is a hydrocarbon derivative that contains the following functional group:
O
R

C
O
R’
Esters are formed by a reaction between a carboxylic acid and an alcohol. To name
an ester, the name of the carboxylic acid and alcohol is used as a combination.
O
O
+
R
C
O
H
carboxylic acid

+
H
O
alcohol
R’
R
C
ester
O
R’
H
O
H
water
Naming and Drawing Esters:
 Identify the root
Identify the part of the ester that contains the C = O group. The root of the
name of the ester is based on the name of the acid. Determine the name of
the parent acid.
 Identify the suffix
Remove the –oic acid from the name of the parent acid and replace it with
–oate.
 Identify the prefix
The name of the alkyl group originating from the alcohol is the prefix for
the name of the ester.
There is always a space between the name of the alkyl group and the root.

EX. Name the following compound

EX. Name the following compound

EX. Name the following compound

EX. Name the following compound

EX. Draw the structure of ethyl butanoate

EX. Draw the structure of methyl propanoate

EX. Draw the structure of butyl 2-methylpropanoate
Physical Properties of Esters

The C=O group makes esters somewhat polar but without the –OH group, ester
molecules cannot form hydrogen bonds with one another. Therefore, their boiling
points are much lower than similar sized alcohols and carboxylic acids.

The most noticeable characteristic of esters is their volatility which allows them to
generate aromas.
 Ex. ethyl octanoate (found in oranges) and pentyl ethanoate (found in
bananas)
Chem 30
Carboxylic Acids and Esters
1. Name each of the following molecules:
a)
b)
c)
d)
e)
f)
g)
h)
i)
j)
2. Draw a condensed structural diagram for each of the following:
(a) propyl butanoate
(b) propanoic acid
(c) hexanoic acid
(d) ethyl octanoate
(e) 2-methylpropyl methanoate
(f) 3,4-diethyl-2,3,5-trimethylheptanoic acid
3. Draw a line structural diagram for compound in question 2.