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  4. Ester containing α -hydrogens undergo self condensation in presence of a strong base such as sodium ethoxide to form β -ketoesters. This reaction is called

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Q. Ester containing $\alpha $ -hydrogens undergo self condensation in presence of a strong base such as sodium ethoxide to form $\beta $ -ketoesters. This reaction is called

NTA AbhyasNTA Abhyas 2020Aldehydes Ketones and Carboxylic Acids

Solution:

Ester containing $\alpha $ -hydrogens undergo self condensation in presence of a strong base such as sodium ethoxide to form $\beta $ -ketoesters. This reaction is called Claisen condensation.

$CH_{3}-\overset{O}{\overset{\left|\right. \left|\right.}{C}}-OC_{2}H_{5}+H-\overset{\alpha }{C}H_{2}COOC_{2}H_{5}\overset{C_{2} H_{5} O^{-} N a^{+}}{ \rightarrow }\underset{\left(A \, \beta \text{-keto ester}\right)}{C H_{3} - \overset{O}{\overset{\left|\right. \left|\right.}{C}} - \overset{\alpha }{C} H_{2} C O O C_{2} H_{5}}+C_{2}H_{5}OH$

Crossed-Claisen condensation is feasible only when one of the reactants has no $\alpha $ -hydrogen and is thus incapable of undergoing self condensation. For example

Solution