Question

Which of the alkyl chlorides listed below undergoes dehydrohalogenation in the presence of a strong base to give 2-pentene as the only alkene product ?

• A. 3-chloropentane
• B. 2-chloropentane
• C. 1-chloropentane
• D. 1-chloro-2-methylbutane

Answer 1

The correct option is A 3-chloropentane

When alkyl chloride is heated in presence of strong base it undergo dehydrohalogenation to give alkene product. A strong Base favours E2 reaction as it readily attacks the proton.
The most substituted alkene is the major product according to Saytzeff Rule, generally it is most stable and hence more preferred one.
3-chloropentane gives 2-pentene on dehydrohalogenation.