Question

What is the action of ethane –1, 2–diol on acetone?

Answer 1

When acetone is heated with ethane-1,2-diol in the presence of a small amount of acid (conc. H₂SO₄), it forms a cyclic ketal (acetonide) with elimination of water.

\[\ce{(CH3)2CO + HO - CH2 CH2 - OH ->[H+] (CH3)2C(OCH2CH2O) + H2O}\]

2,2-Dimethyl-1,3-dioxolane (a cyclic ketal) is formed. This reaction is used for the protection of the carbonyl group.