Give the action of the Clemmensen reduction on 2-butenal?

    CLEMMENSEN REDUCTION
    The Clemmensen Reduction involves adding ##Zn(Hg)## dissolved in heated ##HCl## to something reducible. Note though that this process can accidentally chlorinate a double bond also present on the reactant.
    The principal action of the Clemmensen Reduction is to reduce a ##-stackrel(O)stackrel(||)C-## to a ##-CH_2-## or ##-stackrel(O)stackrel(||)C-H## to a ##-CH_3##.
    So using it on 2-butenal is supposed to turn it into 2-butene.
    But when you have ##HCl## a strong acid in the presence of a double bond there’s a good chance it’ll protonate the double bond. At that point a hydrochlorination would happen across the double bond forming an alkyl chloride.
    That’s why if you wanted to remove the carbonyl oxygen you should do a similar reduction in basic media and the Wolff-Kischner reduction qualifies.
    WOLFF-KISHNER REDUCTION
    The basic counterpart to the acidic Clemmensen reduction is the Wolff-Kishner reduction which is run in base. It aims to accomplish the same thing but in different sometimes more favorable conditions.
    The general reactants are hydrazine (##H_2N-NH_2##) and a strong base like ##NaOH##.
    WOLFF-KISHNER VS. CLEMMENSEN
    The main benefit of the Wolff-Kishner reduction is that because it’s in base it wouldn’t accidentally protonate a hydroxyl group or double bond in the reactant and allow side reactions to occur for acid-sensitive reagents.
    Confer with a reaction involving a hydroxyaldehyde reactant (Organic Chemistry Bruice Ch. 15.18) and you would see the following conundrum is resolved by choosing one reduction method over the other:

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