Which alkyl halides form the carboxylic acids listed here after reaction with sodium cyanide followed by heating the product in an acidic aqueous solution?
a. butyric acid
b. isovaleric acid

Verified step by step guidance

1. Identify the structure of the carboxylic acids given in the problem. Butyric acid is a four-carbon carboxylic acid with the formula CH₃CH₂CH₂COOH, and isovaleric acid is a five-carbon branched carboxylic acid with the formula (CH₃)₂CHCH₂COOH.
2. Understand the reaction sequence. The reaction involves two steps: (1) substitution of the halide in the alkyl halide with a cyanide group (–CN) using sodium cyanide (NaCN), and (2) hydrolysis of the nitrile group (–CN) in acidic aqueous solution to form a carboxylic acid.
3. Determine the alkyl halide precursor for butyric acid. The nitrile intermediate for butyric acid is CH₃CH₂CH₂CN. To form this nitrile, the corresponding alkyl halide must be CH₃CH₂CH₂Br or CH₃CH₂CH₂Cl, where the halide group is replaced by –CN in the first step.
4. Determine the alkyl halide precursor for isovaleric acid. The nitrile intermediate for isovaleric acid is (CH₃)₂CHCH₂CN. To form this nitrile, the corresponding alkyl halide must be (CH₃)₂CHCH₂Br or (CH₃)₂CHCH₂Cl, where the halide group is replaced by –CN in the first step.
5. Summarize the process: For butyric acid, the alkyl halide is CH₃CH₂CH₂X (where X = Br or Cl). For isovaleric acid, the alkyl halide is (CH₃)₂CHCH₂X (where X = Br or Cl). These alkyl halides undergo substitution with NaCN to form nitriles, followed by hydrolysis to yield the carboxylic acids.

Key Concepts

Alkyl Halides

Alkyl halides are organic compounds containing a carbon atom bonded to a halogen atom (F, Cl, Br, I). They are important intermediates in organic synthesis and can undergo nucleophilic substitution reactions, where the halogen is replaced by a nucleophile. Understanding the structure and reactivity of alkyl halides is crucial for predicting the products of reactions involving these compounds.

Nucleophilic Substitution Reaction

Nucleophilic substitution reactions involve the replacement of a leaving group (like a halogen) by a nucleophile, such as cyanide ions (CN-). This reaction is fundamental in organic chemistry, particularly in the synthesis of carboxylic acids from alkyl halides. The mechanism can follow either an SN1 or SN2 pathway, depending on the structure of the alkyl halide and the conditions of the reaction.

Carboxylic Acid Formation

Carboxylic acids are organic compounds characterized by the presence of a carboxyl group (-COOH). In the context of the question, the reaction of alkyl halides with sodium cyanide followed by hydrolysis in acidic conditions leads to the formation of carboxylic acids. This transformation is significant in organic synthesis, as it allows for the conversion of simpler alkyl halides into more complex carboxylic acids.