Question

2-Bromobutane to but-2-ene

Hint:

An E2 elimination mechanism involves the simultaneous removal of a proton and a leaving group, resulting in the formation of an alkene.

Answer 1

Synthesis of But-2-ene from 2-Bromobutane

The transformation of 2-bromobutane to but-2-ene is achieved via an elimination reaction, specifically the E2 mechanism. This process necessitates the presence of a strong base, such as potassium hydroxide (KOH).

During the E2 reaction, the base removes a proton from the β-carbon (adjacent to the carbon bearing the bromine atom). Concurrently, the bromine atom departs, leading to the simultaneous formation of a double bond, thereby creating an alkene.

Reaction Scheme:

\( \text{CH}_3\text{-CHBr-CH}_2\text{-CH}_3 \xrightarrow{\text{alc. KOH, heat}} \text{CH}_3\text{-CH=CH-CH}_3 \)

Resulting Product: But-2-ene is the predominant product, adhering to Zaitsev’s rule, which dictates a preference for the formation of the more substituted alkene.