JEE Main · 2021 · 20 Jul 2021 · Shift 2 · Hydrocarbons

Metallic sodium does not react normally with:

(A)gaseous ammonia
(B)tert - butyl alcohol
(C)But - 2 - yne✓ Correct
(D)Ethyne

Answer: (C)

Solution

Sodium metal reacts with a compound that holds a hydrogen acidic enough to be displaced, and hydrogen gas is set free. Ammonia has N-H bonds and gives sodamide, ethyne has a hydrogen on an

s p

carbon that holds the electron pair tightly enough to make it acidic and gives sodium acetylide, and tert-butyl alcohol, hindered though it is, still has an O-H bond and gives the alkoxide. But-2-yne carries a methyl group on each of the two triply bonded carbons, so it has no hydrogen on an

s p

carbon and nothing acidic enough for sodium to remove. Metallic sodium does not react normally with but-2-yne.

JEE Main · 2021 · 20 Jul 2021 · Shift 2 · Single correct option

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