This module I am answering asked me to provide a reason why Wolff–Kishner reduction is favored over Clemmensen reduction in reducing (3Z)-pent-3-enal to (2Z)-pent-2-ene but either Wolff–Kishner or Clemmensen can be used to reduce pentanal to pentene.

I am currently running with the notion that the alkene substituent double bond's reactivity is the reason behind this since acid is used in Clemmensen reduction compared to Wolff–Kishner's base, and it might interfere with this alkene substituent instead of the carbonyl group in aldehyde. Is this notion correct?

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    $\begingroup$ Correct, the cHCl conditions can add the elements of water or HCl across the double bond or just isomerise it $\endgroup$ – Waylander Jan 9 at 16:27
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    $\begingroup$ Why is the Wolff-Kishner preferred? Isomerization of the aldehyde or hydrazone is likely in basic medium. $\endgroup$ – user55119 Jan 9 at 17:21
  • $\begingroup$ Doesn't it depend if you have 1,2 vs 1,4 addition? Hydrazine is a strong nucleophile. Also enolizable carbonyls can create an unholy mess in these reactions $\endgroup$ – Beerhunter Jan 10 at 17:25

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