Question

Given below are two statements:
Statement (I) : S$_N$2 reactions are 'stereospecific', indicating that they result in the formation only one stereo-isomers as the product.
Statement (II) : S$_N$1 reactions generally result in formation of product as racemic mixtures.
In the light of the above statements, choose the correct answer from the options given below :

• A. Statement I is true but Statement II is false
• B. Statement I is false but Statement II is true
• C. Both Statement I and Statement II is true
• D. Both Statement I and Statement II is false

Answer 1

The Correct Option is C

To evaluate the given statements regarding S_N2 and S_N1 reactions, let's delve into the concepts:

1. Statement (I): S_N2 reactions are 'stereospecific', indicating that they result in the formation of only one stereoisomer as the product.

Explanation: S_N2 reactions involve a one-step, bimolecular nucleophilic substitution mechanism. The nucleophile attacks the carbon atom from the side opposite to the leaving group, leading to an inversion of configuration at the chiral center, known as the Walden inversion. Thus, the product is stereospecific as it results in a specific stereoisomer.

1. Statement (II): S_N1 reactions generally result in the formation of products as racemic mixtures.

Explanation: S_N1 reactions occur via a two-step mechanism where the first step involves the formation of a carbocation intermediate. Since the carbocation is planar, the nucleophile can attack from either face of the carbocation, leading to the formation of both enantiomers in equal proportion. As a result, the product is a racemic mixture.

Thus, both statements I and II are accurate as per the standard chemical reaction mechanisms for S_N2 and S_N1 reactions. Therefore, the correct answer is:

Both Statement I and Statement II is true

Answer 2

S$_\text{N}2$ reactions are stereospecific and proceed via a backside attack, resulting in the inversion of configuration at the chiral center.
S$_\text{N}1$ reactions occur via a carbocation intermediate, which is planar. As a result, nucleophiles can attack from either side, leading to a racemic mixture of products.
Thus:
\[ \text{S$_\text{N}2$} \rightarrow \text{Inversion (stereospecific)}, \quad \text{S$_\text{N}1$} \rightarrow \text{Racemization}. \]
Both statements are correct.