Question

Which of the following reaction will not produce \(1^{\circ}\) amine? (a) (b) (c) (d)

Short answer

Based on the analysis of the example reactions, reaction (d) is the one that does not produce a 1° amine.

Step-by-step solution

Analyze Reaction (a)

In reaction (a), the reaction involves the reduction of a cyano group R-CN to a primary amine R-NH₂. The formation of a 1° amine is expected in this reaction.

Analyze Reaction (b)

In reaction (b), the reaction involves nucleophilic substitution of an alkyl halide R-Cl with NaNH₂. The resulting product is a 1° amine, R-NH₂. Thus, this reaction will produce a primary amine.

Analyze Reaction (c)

In reaction (c), the reduction of a nitro group R-NO₂ is taking place. It will be converted into a primary amine, R-NH₂. Therefore, this reaction will produce a primary amine.

Analyze Reaction (d)

In reaction (d), an acid chloride R-C(O)Cl reacts with NH₃ to form an amide, R-CONH₂. This product is not a primary amine, so this reaction will not produce a 1° amine. #Conclusion#Based on the analysis of the example reactions, reaction (d) is the one that does not produce a 1° amine.

Key concepts

Reduction of Cyano Groups

The reduction of cyano groups is a crucial transformation in organic chemistry for the synthesis of primary amines. A cyano group, represented as -CN, consists of a carbon triple-bonded to a nitrogen atom. When a compound containing this group undergoes reduction, it converts into a primary amine with the general formula R-NH₂.

This reduction can be achieved using various reducing agents such as hydrogen in the presence of a metal catalyst (e.g., Ni, Pd, or Pt), sodium in ethanol (known as the Bouveault-Blanc reduction), or lithium aluminum hydride (LiAlH₄), among others. The process involves the addition of hydrogen atoms or their equivalents to the carbon and nitrogen atoms of the cyano group, breaking the triple bond and forming a single C-N bond with additional hydrogen atoms attached.

Nucleophilic Substitution Reactions

Nucleophilic substitution reactions are fundamental processes where a nucleophile (a species that donates an electron pair) displaces another group in a molecule. In the context of primary amine synthesis, these reactions commonly involve alkyl halides, where the halide (X) acts as the leaving group.

A common nucleophile in these reactions is the amide ion, NH₂⁻, which can be derived from ammonia (NH₃). When NH₂⁻ attacks an alkyl halide, it replaces the halide to form a new compound, a primary amine (R-NH₂). This type of reaction is sensitive to the nature of the alkyl halide and the reaction conditions, as various factors like steric hindrance and the strength of the nucleophile can affect the outcome.

Reduction of Nitro Groups

The reduction of nitro groups to primary amines is another significant chemical conversion. The nitro group, noted as -NO₂, is a functional group featuring a nitrogen atom double-bonded to one oxygen and single-bonded to another oxygen atom.

When reduced, the nitro group is converted into an amino group (-NH₂). This reduction often employs reagents such as palladium on carbon (Pd/C) with hydrogen gas (H₂), iron in acidic conditions, or other reducing agents like stannous chloride (SnCl₂) or zinc with a mineral acid. During the reaction, the oxygen atoms are removed, and hydrogen atoms are added to the nitrogen, forming a primary amine. This reaction is valuable for the construction of more complex amine-containing molecules in both pharmaceutical and dyestuff chemistry.

Amide Formation

Amides are commonly formed by the reaction of carboxylic acids or their derivatives with amines. In this case, amide formation is specifically highlighted through the reaction of an acid chloride with ammonia. Acid chlorides, represented as R-C(O)Cl, are highly reactive due to the presence of the electronegative chlorine atom.

When treated with ammonia (NH₃), the chlorine is displaced, and an amide (R-CONH₂) is formed. Unlike primary amines, amides contain a carbonyl group (C=O) directly bonded to a nitrogen atom. This reaction does not yield a primary amine but results in an amide, which can be an intermediate or a final product in various organic synthesis applications, including the production of pharmaceuticals, polymers, and more.