Question

● When 1,4-butane diol on dehydration by heating in presence of sulphuric acid or alumina gives?

Answer

A. O 1,2-Butadiene

B. O 1,3-Butadiene

:. O Two molecules of Ethene

D. O 2-Butene

Answer 1

Answer:

Primary alcohols undergo bimolecular elimination (E2 mechanism).

Oxygen donates two electrons to a proton from sulfuric acid H

2

SO

4

, forming an alkyloxonium ion. Then the nucleophile HSO

4

–

back-side attacks one adjacent hydrogen and the alkyloxonium ion leaves in a concerted process, making a double bond. There is no rearrangement in bimolecular reactions.

The product is 1−Butene