Esters

1
Esters

• Uses
• Flavourings
• Perfumes
• Solvents

2
What are Esters?

• Chemicals made in the reaction of an alcohol and
  a carboxylic acid
• Contain the ESTER functional group
• This is an example of a CONDENSATION REACTION
• - 2 molecules joining up, releasing water

ESTER
WATER
3
General equation
Alcohol Carboxylic acid
Alkanol Alkanoic acid
4

• The OH is removed from the ACID
• The H is removed from the ALCOHOL

Using SSF

• The C with H atoms attached is from the alcohol
• The C without H atoms attached is from the acid

In the two examples which follow use both full
and shortened structural formulae to show the
formation of the ester
a) Butanoic acid Methanol
b) Methanoic acid Pentanol
5
Naming Esters

• The first part comes from the ALCOHOL

Ethanol
Ethyl
Pentanol
Pentyl
Hexanol
Hexyl

• The second part comes from the ACID

Ethanoic acid
Ethanoate
Butanoic acid
Butanoate
Hexanoic acid
Hexanoate
6
Practice
Name the Esters formed from
1. Methanoic acid and Pentanol
Pentyl methanoate
2. Propanoic acid and Methanol
Methyl propanoate
3. Butanol and Octanoic acid
Butyl octanoate
4. Ethanol and Salicylic acid
Ethyl salicylate
7
Name the following esters from the structures
Propyl
methanoate
H
CH3CH2COOCH2CH3
Ethyl
propanoate
8
Making Esters in the lab
As the mixture is added to the sodium
hydrogencarbonate solution, there is fizzing
and the ester forms as an immiscible layer and
can be recognised by a distinctive sweet/fruity
smell
9
Breaking Esters in the lab

• The making of an ester can be reversed
• The ester is heated with a dilute alkali
• This opposite process is called HYDROLYSIS
  (break-down, using water)

10
General equation
Alcohol Carboxylic acid
Alkanol Alkanoic acid
11
Breaking Esters
Ethanoic acid
Ethanol
The break point is between the C with a single
bond to O in the Ester Group
To the C atom with a double bond to O (ie the C
O) add an OH group to produce the parent
carboxylic acid
To the C atom with a single bond to O (ie the C
O) add an H atom to produce the parent alcohol
CH3COOCH2CH2CH3
CH3COOH
CH3CH2CH2OH
Ethanoic acid
Propan 1- ol
12
Practice
Name the parent alcohol and carboxylic acid and
draw their structures for the esters below
CH3CH2CH2CH2COOCH2CH2CH2CH2CH3