Q.What is the product of the following reaction? CH3-C(triple bond)CH + H2O --(HgSO4 / dil. H2SO4, 60 deg C)-->

Hydration of Alkynes (Kucherov Reaction)

The Kucherov reaction is the acid-catalysed hydration of alkynes. When an alkyne is treated with dilute sulphuric acid in the presence of mercuric sulphate ($HgSO_4$) as catalyst, water adds across the triple bond to give a carbonyl compound (an aldehyde or a ketone).

Water adds according to Markovnikov's rule, first forming an unstable enol, which immediately tautomerises to the more stable keto form:

Acetylene is the special case. Because it is the only alkyne with hydrogen on both triple-bond carbons, its hydration gives an aldehyde — acetaldehyde:

All higher (non-terminal or terminal) alkynes give ketones. For example, propyne yields acetone (propan-2-one):

$CH_3-C\equiv CH + H_2O \xrightarrow{HgSO_4/H_2SO_4} CH_3-CO-CH_3$ …