Question

Which of the following is a correct feature of the \(\text{SN}^2\) mechanism?

• A. The \(\text{SN}^2\) mechanism proceeds mainly with racemization.
• B. The \(\text{SN}^2\) mechanism includes a transition state with penta coordinating carbon.
• C. The \(\text{SN}^2\) mechanism involves formation of planar carbocation intermediate in the first step.
• D. The \(\text{SN}^2\) mechanism involves formation of carbocation with \(\text{SP}^2\) hybridized carbon.

Hint:

SN2 is a one step process with a pentacoordinate transition state and inversion.

Answer 1

The Correct Option is B

Step 1: Recall
SN2 is concerted: bond making and bond breaking occur together.

Step 2: Features
Pentacoordinate transition state, inversion of configuration, no intermediate.

Step 3: Compare
Racemisation and carbocations belong to SN1, so only (B) fits.

Final Answer:
Option (B). \[ \boxed{\text{Pentacoordinate transition state}} \]