Q. Hydrolysis of an ester gives a carboxylic acid which on Kolbes electrolysis yields ethane. The ester is :
EAMCETEAMCET 1997
Solution:
Hydrolysis of $ \text{C}{{\text{H}}_{\text{3}}}\text{COOC}{{\text{H}}_{\text{3}}} $ (methyl ethanoate) gives acetic acid and methyl alcohol. Acetic acid on electrolysis by Kolbes method gives ethane. So, the ester is methyl ethanoate. $ \underset{\text{Methyl}\,\text{ethanoate}}{\mathop{C{{H}_{3}}CO}}\,\,OH\xrightarrow{{}} $ $ \underset{\text{Acetic}\,\text{acid}}{\mathop{C{{H}_{3}}COOH+}}\,C{{H}_{3}}OH $ Kolbes electrolysis: $ \underset{\text{Acetic}\,\text{acid}}{\mathop{C{{H}_{3}}COOH}}\,\xrightarrow{{}}C{{H}_{3}}CO{{O}^{-}}+{{H}^{+}} $ At anode:
or $ \underset{(Ethane)}{\mathop{C{{H}_{3}}-C{{H}_{3}}}}\, $ At cathode: $ {{H}^{+}}+{{e}^{-}}\xrightarrow{{}}H $ $ H+H\xrightarrow{{}}{{H}_{2}}\uparrow $
