\(\mathrm{R}-\mathrm{Cl}+\mathrm{AgCN} \longrightarrow \mathrm{A} \stackrel{\text { reductions }}{\longrightarrow} \mathrm{B}\) \(\mathrm{A}\) and \(\mathrm{B}\) respectively are: (a) \(\mathrm{RCN}, \mathrm{RCH}_{2} \mathrm{NH}_{2}\) (b) RNC, RNHCH \(_{3}\) (c) \(\mathrm{RCN}, \mathrm{RNHCH}_{3}\) (d) \(\mathrm{RNC}, \mathrm{RCH}_{2} \mathrm{NH}_{2}\)

Alkyl halides, often referred to as haloalkanes, are organic compounds containing a halogen atom attached to an aliphatic carbon chain. They are known for their reactivity, particularly in nucleophilic substitution reactions, which make them valuable in organic synthesis.

In a nucleophilic substitution reaction, a nucleophile, which is a species rich in electrons, replaces a leaving group in the molecule. The leaving group is typically a halide ion, such as chloride (Cl-) in an alkyl chloride (R-Cl). This reaction type is crucial in the synthesis of a wide range of organic compounds, including alcohols, ethers, and amines.

Common Mechanisms

• SN1 reaction: Unimolecular nucleophilic substitution, where the rate depends only on the concentration of the alkyl halide.
• SN2 reaction: Bimolecular nucleophilic substitution, occurring with a 'backside attack' by the nucleophile and leading to an inversion of stereochemistry at the carbon atom.

In our context, the alkyl halide R-Cl undergoes an SN2 reaction with AgCN, where the CN group acts as the nucleophile, leading to the formation of an alkyl cyanide (RCN). The choice of nucleophile and reaction conditions can highly influence the outcome, making alkyl halides quite versatile reagents.

The nitrile group, characterized by a carbon triple-bonded to a nitrogen (–C≡N), is a functional group that can undergo various chemical transformations. This functionality is interesting due to its versatility, especially in the synthesis of carboxylic acids, amines, amides, and other nitrogen-containing compounds.

Conversion of nitriles into different functional groups can be achieved through several types of reactions:

• Hydrolysis: Nitriles can be hydrolyzed under acidic or basic conditions to form carboxylic acids.
• Reduction: Nitriles can be reduced to primary amines using strong reducing agents like lithium aluminum hydride (LAH).
• Grignard reaction: Nitriles can react with Grignard reagents to form ketones, which can further be reduced to secondary alcohols.

In our exercise, the conversion of a nitrile group (–C≡N) to a primary amine (-CH2NH2) involves a reduction reaction. This kind of transformation is fundamental in organic chemistry, allowing for the buildup of molecular complexity from simpler building blocks.

Primary amines are organic compounds featuring an amino group (-NH2) connected to a carbon atom that is not attached to any other carbon atoms. These amines are at the forefront when building various nitrogen-containing molecules, including pharmaceuticals, dyes, and agrochemicals.

Several methods exist for the synthesis of primary amines:

• Ammonolysis of alkyl halides: Treating alkyl halides with ammonia can yield primary amines, though secondary and tertiary amines can also form as side products.
• Reductive amination: Aldehydes or ketones react with ammonia or primary amines in the presence of a reducing agent to afford primary amines.
• Reduction of nitriles: As seen in our exercise, reducing a nitrile group with hydrogen or a suitable reducing agent such as LAH results in a primary amine.

The specific context of our exercise revolves around the reduction of a nitrile group (RCN) to synthesize a primary amine (RCH2NH2). Understanding the reductive process and the choice of suitable reducing agents is essential for controlling the outcome of the reaction and obtaining the desired amine with high yield and purity.