Number of possible crossed Claisen ester condensation products in the given reaction is?${\mathrm{CH}}_3{\mathrm{COOC}}_2{\mathrm{H}}_5+{\mathrm{CH}}_3-{\mathrm{CH}}_2- {\mathrm{COOC}}_2 {\mathrm{H}}_5\underset{{\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}}{\overset{{\mathrm{C}}_2{\mathrm{H}}_5\mathrm{ONa}}{\to }}$

Here, we have ethyl acetate and ethyl propanoate. Each ester have a acidic α−hydrogen. So each ester will undergo self condensation to form a product. Also enolate formed from ethyl acetate attacks ethyl proponoate to form a product and enolate of ethyl proponoate will attack ethyl acetate to form a product.

Hence, totally we can get 4 possible products with claisen condensation reaction.