The hydrocarbon which can react with sodium in liquid ammonia is?

(A) $\ce{CH3CH2C#CH}$
(B) $\ce{CH3CH=CHCH3}$
(C) $\ce{CH3CH2C#CCH2CH3}$
(D) $\ce{CH3CH2CH2C#CCH2CH2CH3}$


(A) $\ce{CH3CH2C#CH}$


I am confused why the answer cant be (C) or (D) since these two could undergo reaction with sodium in ammonia to give me trans-alkenes as products.

  • $\begingroup$ Well, I guess they missed this possibility. $\endgroup$
    – Mithoron
    Commented Apr 26, 2021 at 14:00
  • 1
    $\begingroup$ Similar to this (even poorer) question Similar to chemistry.stackexchange.com/questions/94716/…. The one marked in red in the picture that you have included is the only which doesn't occur. $\endgroup$
    – Alchimista
    Commented Apr 26, 2021 at 14:01
  • $\begingroup$ @Alchimista Ah so i think the question itself has ambiguity. Also yes, i know the second reaction wont undergo birch reduction, i mis clicked option lol. $\endgroup$ Commented Apr 26, 2021 at 14:06
  • $\begingroup$ @Alchimista Nicely found. Well, I guess we can safely close this as a dupe and solve the $\ce{#CH3}$ mystery once and for all. $\endgroup$
    – andselisk
    Commented Apr 26, 2021 at 14:19
  • 2
    $\begingroup$ Poorer in my first comment referred to the quiz not really to the SE questions. @Andselisk yes its a kind of duplicate. $\endgroup$
    – Alchimista
    Commented Apr 27, 2021 at 8:48

1 Answer 1


You are correct.

Na/NH3 is a standard method for reducing internal alkynes to trans (E) alkenes.

More reading here and here


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