Question

Aklyl group in Grignard reagent serve as

• A. Carbene
• B. Free radical
• C. Aromatic carbocation
• D. Carbanion

Answer 1

The Correct Option is D

The question relates to the role of the alkyl group in a Grignard reagent. Understanding the nature of Grignard reagents is crucial for determining the correct answer.

A Grignard reagent is typically expressed with the formula R-MgX, where R is the alkyl or aryl group and X is a halogen. The key feature of the Grignard reagent is the highly polar bond between the carbon and magnesium atoms. This polar bond makes the alkyl group behave as a nucleophile.

Let's break down the options:

• Carbene: A carbene is a neutral species featuring a carbon atom with two valence electrons that is typically divalent and highly reactive. Grignard reagents do not contain carbenes.
• Free radical: Free radicals are atoms or molecules with unpaired electrons. Grignard reagents do not function through free radical mechanisms under normal conditions.
• Aromatic carbocation: Carbocations are positively charged species with a full positive charge on the carbon atom. Since Grignard reagents provide nucleophilic (negative) carbon for reactions, they do not form carbocations.
• Carbanion: Carbanions possess a negatively charged carbon atom. In Grignard reagents, the alkyl group behaves like a carbanion due to the electron-rich character of the carbon atom, making it a powerful nucleophile.

Therefore, the correct answer is that the alkyl group in Grignard reagents acts as a carbanion. This provides the essential nucleophilic characteristic necessary for reactions such as nucleophilic additions to carbonyl groups.

In summary, the alkyl group in a Grignard reagent acts as a nucleophile, resembling a carbanion, due to its electron-rich nature. This behavior is instrumental in organic synthesis, enabling various carbon-carbon bond-forming reactions.