Carboxylic acids, esters, amines, and amides

an acid catalyst used usually sulphuric acid A condensation reaction The condensation reaction between the hydroxyl group and the carboxylic acid known as esterification.. Named after

Esters C.I 13.5

What are they?

How are they made?

Formed when an alcohol reacts with a

carboxylic acid

Very slow reaction, unless! an acid catalyst used (usually sulphuric acid)

A condensation reaction

The condensation reaction between the

hydroxyl group and the carboxylic acid

known as esterification

Reverse reaction = ester hydrolysis

Named after alcohol & carboxylic acid from which they are derived

Names of esters

end in –oate.

CH3

C

CH2 O

O

CH3

ethyl ethanoate

this part from the acid and is named after it

this part comes from the

alcohol & is named after it

let’s name some esters!

Structural formulae

Although the previous structural formula are the clearest way of showing esters, they can draw out in a

shortened form.

ethyl ethanoate

CH3 C

CH2 O

O

CH3

Either…

Or…

CH3

C O CH2

O

CH3

In this version the acid part has been written first

 Identify the group attached to the C=O – this is from

the acid

 The group attached to the –O- is from the alcohol.

Wait! What’s that smell?

• Esters have strong, sweet smells.

• Their bouquet is often floral or fruity.

• This means they are used in food flavourings &

perfumes.

• Also, very good at dissolving organic compounds so often used as solvents.

ester fragrance

ethyl methanoate raspberries

3-methylbutyl ethanoate pears

ethyl 2-methylbutanoate apples

phenylmethyl ethanoate jasmine

Esters from phenols

• -OH group in phenol less reactive

to esterification, requires a more

vigourous reagent.

• Use of ethanoic acid in

esterification is also known as

ethanoylation.

• Ethanoic anhydride is a more

vigourous ethanoylating agent

OH

Esters from phenols

• Ethanoic anhydride used as it is reactive

but not too dangerous

• Ethanoyl chloride is much more reactive,

but, also toxic and hazardous to

use

• Ethanoic anhydride & ethanoyl chloride

are described as acylating agents

 using an acylating agent is the only way to esterify a phenol

 alcohols can be esterified using acylating agents or by reacting with a carboxylic acid.

Ester hydrolysis

Breakdown of an ester by water

Process sped up by catalysis

Can use an acid to catalyse (H2SO4)

Alkali catalysts (e.g sodium hydroxide) can also be used but instead of producing

carboxylic acid a carboxylate salt is

formed

Alkaline hydrolysis goes to completion &

hence is usually preferred

This is why it is a condensation reaction because water is produced!

R

R’

C

H2O

+

O H

H O

R O

O

+

⇋

Definition of a condensation reaction = two molecules reacting to form a larger molecule with the elimination of a

small molecule such as water

CH

CH2 O

O

CH3

CH2

C

CH3 O

O

CH

CH O

O

ethyl methanoate

methyl propanoate

methyl methanoate

R’

C

H2O

+

O H

H O

R O

O

+

⇌

FORWARD REACTION = condensation reaction, the esterification of an alcohol using

acid catalyst under reflux.

REVERSE REACTION = ester hydrolysis, same catalyst works for both forward & reverse reactions.

OH

OH - →

CH3

C

CH2 O

O

CH3

ethyl ethanoate

+

CH2

CH3

CH3

C

- O O ethanol

ethanoate ion

not a reaction that exists

in equilibrium (unlike using acid catalyst)