Question

Which of the following is least reactive in a nucleophilic substitution reaction?

• A. $(CH_3)_3C-Cl$
• B. $CH_2 =CHCl$
• C. $CH_3CH_2Cl$
• D. $CH_2 =CHCH_2Cl$

Answer 1

The Correct Option is B

The question asks which compound is the least reactive in a nucleophilic substitution reaction. Let's analyze each option:

1. $(CH_3)_3C-Cl$: This compound is also known as tert-butyl chloride. It is a tertiary alkyl halide, which typically undergoes nucleophilic substitution reactions relatively slowly because of steric hindrance around the carbon atom bonded to chlorine.
2. $CH_2 =CHCl$: This is vinyl chloride, where the chlorine atom is directly attached to a carbon-carbon double bond. In such cases, the carbon bearing the chlorine doesn't possess the sp³ hybridization that facilitates a typical nucleophilic substitution. As a result, the electron-rich nucleophile finds it difficult to attack the electron-rich double bond, making it less reactive in nucleophilic substitution reactions.
3. $CH_3CH_2Cl$: This compound is ethyl chloride, a primary alkyl halide, which generally participates in nucleophilic substitution reactions more readily than tertiary alkyl halides because there is less steric hindrance.
4. $CH_2 =CHCH_2Cl$: Known as allyl chloride, this compound has a chlorine atom attached to an allylic position. Such allylic halides are generally more reactive in nucleophilic substitution reactions due to resonance stability provided by the allylic system.

Based on the analysis, $CH_2 =CHCl$ (\textit{vinyl chloride}) is the least reactive in nucleophilic substitution reactions because of its electron-rich double bond, which repels nucleophiles. The correct answer is $CH_2 =CHCl$.