Esters are polar molecules that can participate in hydrogen bonding and dipole-dipole interactions. They are more polar than ethers but less polar than alcohols. Esters have lower melting and boiling points than the corresponding acids and amides. They undergo hydrolysis under basic conditions and are relatively resistant to reduction compared to ketones and aldehydes. Esters are commonly used as solvents, plasticizers, and food flavorings.

1. Physical Properties of Esters
 Esters are polar molecules and exhibits dipole-dipole interaction as well as
van der Waals.
 Esters are more polar than ethers but less polar than alcohols.
 They participate in hydrogen bonds as hydrogen-bond acceptors
(recipient), but cannot act as hydrogen-bond donors, unlike their parent
alcohols.
 This ability to participate in hydrogen bonding confers some water-solubility
(fairly soluble in water).
 Esters are more volatile (volatility is the tendency of a substance to
vaporize) than carboxylic acids of similar molecular weight.
 Esters have lower melting point and lower boiling point than the
corresponding amides.

2. Chemical Properties of Esters
 Addition of nucleophiles at carbonyl:
- Esters undergo hydrolysis(Hydrolysis means reaction with water) Under
basic conditions, hydroxide acts as a nucleophile, while an alkoxide is the
leaving group. This reaction is the basis of soap making, saponification (is a
process that produces soap).

3. Chemical Properties of Esters
 Reduction:
-Compared to ketones and aldehydes, esters are relatively resistant to
reduction (reduction refers to all chemical reactions in which atoms have
their oxidation state changed).
 Ester pyrolysis:
-is a vacuum pyrolysis reaction converting esters containing a β-hydrogen
atom into the corresponding carboxylic acid and the alkene.

4. Sources of Esters
Sources of Esters
1.)Making esters from carboxylic acids and
alcohols(Esterfication)
 -Esters are produced when carboxylic acids are
heated with alcohols in the presence of an acid
catalyst (conc. H2S04).
2.) Making esters from alcohols and acid
chlorides
 If you add an acid chloride to an alcohol, you get
a vigorous (even violent) reaction at room
temperature producing an ester and clouds of
steamy acidic fumes of hydrogen chloride.

5. Uses of Esters
Solvents
 Esters have no free OH groups and so they tend to
be insoluble in water. However, they are very good
solvents for polar organic compounds, such as
lacquers, printing ink, polystyrene and cement, as
well as being used in the pharmaceutical industry.
Plasticizers
 Plasticizers are added to plastics to make
themselves better plastics and more flexible. Loss of
these additives over time means they become
brittle. Esters of benzene and 1,2 dicarboxylic acid
are used in PVC.

6. Uses of Esters
Food flavourings
 Esters have fruity smells and natural fruit
flavours are mixtures of esters and carboxylic
acids. For example: