Question

Which of the following halides would undergo an SN1 reaction the fastest?

Option 1: Methyl chloride
Option 2: Ethyl bromide
Option 3: Isopropyl iodide
Option 4: tert-Butyl chloride

Answer 1

Tert-Butyl chloride would undergo an SN1 reaction the fastest due to the formation of a highly stable tertiary carbocation intermediate.

Step-by-step explanation:

Among the options given, tert-Butyl chloride would undergo an SN1 reaction the fastest. SN1 reactions involve the formation of a carbocation intermediate that is planar and can be attacked by the nucleophile. The rate of SN1 reactions is heavily influenced by the carbocation stability, which increases with the number of alkyl groups attached to the positively charged carbon. Methyl chloride (CH3Cl) is not favored for SN1 reactions due to the lack of carbocation stability. Ethyl bromide (C2H5Br) can form a primary carbocation, which is still not very stable. Isopropyl iodide (CH3CH(CH3)I), while forming a more stable secondary carbocation, is less favored than tert-Butyl chloride (C(CH3)3Cl) which forms a highly stable tertiary carbocation. Thus, tert-Butyl chloride is the best substrate for an SN1 reaction among the given choices.