Explain why aldol condensation of aldehydes with methyl alkyl ketones involves the methyl group in the presence of basic catalyst but attack at the methylene group in the presence of acid catalysts e.g. C_(6)H_(5)-CHO+CH_(3)-CO-CH_(2)-CH_(3)overset(NaOH)underset(H_(2)O)to C_(6)H_(5)CH-CH-CO-C_(2)H_(5) C_(6)H_(5)-CHO+CH_(3)CO-CH_(2)-CH_(3)overset(H_(2)SO_(4))underset(3CH_(3)COOH)to C_(6)H_(5)-CH=underset(CH_(3))underset(|)C-CO-CH_(3)

Explain why aldol condensation of aldehydes with methyl alkyl ketones

1.	Explain why aldol condensation of aldehydes with methyl alkyl ketones involves the methyl group in the presence of basic catalyst but attack at the methylene group in the presence of acid catalysts e.g. C_(6)H_(5)-CHO+CH_(3)-CO-CH_(2)-CH_(3)overset(NaOH)underset(H_(2)O)to C_(6)H_(5)CH-CH-CO-C_(2)H_(5) C_(6)H_(5)-CHO+CH_(3)CO-CH_(2)-CH_(3)overset(H_(2)SO_(4))underset(3CH_(3)COOH)to C_(6)H_(5)-CH=underset(CH_(3))underset(\|)C-CO-CH_(3)
Answer» Solution :Base catalysed aldol condensation proceeds through enolate ION and enolate ion `CH_(2)-CO-CH_(2)R` is morestable than the enolate `CH_(3)-overset(O)overset(\|\|)C-CH-R`. ACID CATALYSE aldol condensation proceeds through the enol and the enol `CH_(3)-overset(OH)overset(\|)C=CH_(2)-R` is more stable than the enol `CH_(2)=overset(OH)overset(\|)C-CH_(2)-R`.