Show how you would accomplish the following syntheses using amides as intermediates. You may use any necessary reagents. (a) benzoic acid --> benzyldimethylamine (b) pyrrolidine --> N-ethylpyrrolidine (c) cyclopentanecarboxylic acid --> cyclopentanecarbonitrile

Verified step by step guidance

1. Step 1: For each synthesis, identify the starting material and the target compound. Recognize that amides will be used as intermediates in the synthesis process.
2. Step 2: (a) To convert benzoic acid to benzyldimethylamine, first convert benzoic acid to benzoyl chloride using thionyl chloride (SOCl2). Then, react benzoyl chloride with dimethylamine to form N,N-dimethylbenzamide. Finally, reduce the amide to benzyldimethylamine using a reducing agent like lithium aluminum hydride (LiAlH4).
3. Step 3: (b) To convert pyrrolidine to N-ethylpyrrolidine, first form an amide by reacting pyrrolidine with an acyl chloride, such as acetyl chloride, to form N-acetylpyrrolidine. Then, perform a reductive alkylation using ethyl iodide and a reducing agent like sodium borohydride (NaBH4) to introduce the ethyl group, forming N-ethylpyrrolidine.
4. Step 4: (c) To convert cyclopentanecarboxylic acid to cyclopentanecarbonitrile, first convert the acid to an amide by reacting it with ammonia to form cyclopentanecarboxamide. Then, dehydrate the amide to a nitrile using a dehydrating agent such as phosphorus pentoxide (P2O5) or thionyl chloride (SOCl2).
5. Step 5: Review each step to ensure that the transformations are chemically feasible and that the reagents used are appropriate for the desired conversions. Consider any potential side reactions and how they might be minimized or avoided.

Key Concepts

Amide Chemistry

Amides are organic compounds derived from carboxylic acids and amines, characterized by the functional group -C(=O)N-. They serve as versatile intermediates in organic synthesis, allowing for the transformation of carboxylic acids into amines or other nitrogen-containing compounds through various reactions, such as reduction or alkylation.

Nucleophilic Substitution Reactions

Nucleophilic substitution reactions involve the replacement of a leaving group in a molecule with a nucleophile. In the context of amides, this can include the alkylation of the nitrogen atom, where a nucleophile attacks the carbon atom of the amide, leading to the formation of new amines or substituted amides, which is crucial for synthesizing compounds like benzyldimethylamine.

Carboxylic Acid Derivatives

Carboxylic acid derivatives, such as esters, amides, and anhydrides, can be transformed into one another through various chemical reactions. Understanding these derivatives is essential for the synthesis of compounds like cyclopentanecarbonitrile from cyclopentanecarboxylic acid, as they dictate the reactivity and pathways available for functional group transformations.