# How to determine anhydrides of acids and bases?

Oct 29, 2016

Anhydrides are functional groups which are basically the derivatives of either acids or bases.

#### Explanation:

Anhydrides are functional groups which are basically the derivatives of either acids or bases. Acid anhydrides will have R-COO-CO-R' pattern where R and R' are alkyl groups. While basic anhydrides will not have such a pattern of atomic or molecular connections.

Oct 29, 2016

If an anhydride produces acid/s on addition of water to it,then the anhydride will be anhydride of acid/s. These are generally oxides of nonmetal

For example

1 .$S {O}_{2} + {H}_{2} O \to {H}_{2} S {O}_{3}$

Here $S {O}_{2}$ forms ${H}_{2} S {O}_{3}$ when reacted with water . So $S {O}_{2}$ is anhydride of ${H}_{2} S {O}_{3}$

2 .${\left(C {H}_{3} C O\right)}_{2} O + {H}_{2} O \to 2 C {H}_{3} C O O H$

Here ${\left(C {H}_{3} C O\right)}_{2} O$ forms $C {H}_{3} C O O H$ when reacted with water . So ${\left(C {H}_{3} C O\right)}_{2} O$ is anhydride of $C {H}_{3} C O O H$

3 .$2 N {O}_{2} + {H}_{2} O \to H N {O}_{2} + H N {O}_{3}$

Here $N {O}_{2}$ forms $H N {O}_{3} \mathmr{and} H N {O}_{2}$ when reacted with water . So $N {O}_{2}$ is mixed anhydride of $H N {O}_{3} \mathmr{and} H N {O}_{2}$

If an anhydride produces base on addition of water to it,then the anhydride will be anhydride of base. These are generally oxides of metal. (Exception: Some higher valent metallic oxides can form acids when treated with water. They should be treated as anhydride of acid)

Example

$C a O + {H}_{2} O \to C a {\left(O H\right)}_{2}$

Here $C a O$ forms $C a {\left(O H\right)}_{2}$ when reacted with water . So $C a O$ is anhydride of $C a {\left(O H\right)}_{2}$