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MHT CET Chemistry Aldehydes and Ketones 2026 MHT CET 2026 (11 April Shift 2)

MHT CET Chemistry Question (2026) — Solution

Question

When ethanal and propanal undergo aldol condensation with dilute NaOH, the pair of products obtained by cross condensation reaction is

Options

  1. A. but-2-enal and 2-methylpent-2-enal
  2. B. but-2-enal and pent-2-enal
  3. C. 2-methylbut-2-enal and pent-2-enal
  4. D. 2-methylbut-2-enal and 2-methylpent-2-enal

Answer

C. 2-methylbut-2-enal and pent-2-enal

Step-by-step solution

Ethanal is CH_3CHO and propanal is CH_3CH_2CHO. Cross aldol condensation occurs when the enolate ion of one aldehyde attacks the carbonyl carbon of the other aldehyde. Case 1: Enolate of ethanal attacks propanal. CH_3CH_2CHO + CH_3CHO OH^- CH_3CH_2CH(OH)CH_2CHO CH_3CH_2CH=CHCHO The product formed is pent-2-enal. Case 2: Enolate of propanal attacks ethanal. CH_3CHO + CH_3CH_2CHO OH^- CH_3CH(OH)CH(CH_3)CHO CH_3CH=C(CH_3)CHO The product formed is 2-methylbut-2-enal. Thus, the pair of products obtained by cross condensation is 2-methylbut-2-enal and pent-2-enal. Answer: 2-methylbut-2-enal and pent-2-enal

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