Dicarboxylic acid

DICARBOXYLIC ACID

Carboxylic acid containing two –COOH grs. is called dicarboxylic acid. In IUPAC they are named by placing suffiw ‘dioic acid’ to the name of parent alkane.

 

Preparation

From ethylene dibromide

Ethylene dibromide on treatment with KCN followed by hydrolysis gives succinic acid

 

From Maleic acid

Maleic acid on reduction with H2 in presence of Ni gives, succinic acid.

Chemical properties

1) Action of heat

Succinic acid on heating above its melting point undergo dehydration to give corresponding anhydride.

2) Action of NaHCO3

Succinic acid on treatment with sodium bicarbonate forms its sodium salt.

3) Action of Ethanol

In presence of acid succinic acid reacts with ethanol to give mono as well as diester.

Uses

It is used as, i) In manufacture of dyes and perfumes ii) In medicine iii) As laboratory reagent in volumetric analysis

Acidic strength of dicarboxylic acid

The dicarboxylic acids are stronger than monocarboxylic acid becasue it has a electron withdrawing (−COOH) group.
The increase in the CH2 group in the compound will decrease the acidic strength of the compound because CH2 is an +I effect group so it will increase the electron density on conjugate base.


Here, oxalic acid doesn't have +I group so it more acidic.
Then, malonic acid has one CH2 and succinic acid has 2 CH2 and adipic acid has 4 CH2.
Therfore the strength of acid follows the order,
Adipic acid<Succinic acid<Malonic acid<Oxalic acid