Question

Give the structure of the product you would expect from the reaction (if any) of 2-butyne with one molar equivalent of HBr. If there is no product, simply draw the reactant, 2-butyne. Note: All structures should be drawn with no bonds between carbon and hydrogen.

Answer 1

(Z)-2-bromo-2-butene is produced here.

Step-by-step explanation:

Reaction of 2-butyne with one equivalent of HBr yields (Z)-2-bromo-2-butene.

In the first step, protonation of triple bond produces a carbocation with a double bond. Two methyl groups present in carbocation remain in opposite side to avoid steric interaction.

In the second step, a bromide ion gives nucleophilic addition reaction with carbocation to give (Z)-2-bromo-2-butene.

Full reaction mechanism has been shown below.