Problem 40 - 43 Years JEE ADVANCED (1978-2020) + JEE MAIN Chapterwise & Topicwise Solved Papers Chemistry

Question

The compound which on reaction with aqueous nitrous acid at low temperature produces an oily nitrosoamine is(a) methylamine (b) ethylamine (c) diethylamine (d) triethylamine

Step-by-Step Solution

Answer

(c) Diethylamine forms an oily nitrosoamine with nitrous acid.

Step 1: Understanding the Reaction

The reaction in question involves the formation of nitrosoamines upon reaction with nitrous acid. Primary aliphatic amines ( extit{e.g., methylamine, ethylamine}) typically form alcohols and nitrogen gas, whereas secondary aliphatic amines ( extit{e.g., diethylamine}) can form nitrosoamines, which are oily liquids. Tertiary amines ( extit{e.g., triethylamine}) typically do not form nitrosoamines.

Step 2: Identify Amines

List the given amines: (a) Methylamine, a primary amine (b) Ethylamine, a primary amine (c) Diethylamine, a secondary amine (d) Triethylamine, a tertiary amine.

Step 3: Assess Reaction Pathway

Primary amines (a) methylamine and (b) ethylamine typically react with nitrous acid to produce alcohols, whereas secondary amine (c) diethylamine can produce an oily nitrosoamine. Tertiary amine (d) triethylamine does not react with nitrous acid to produce a nitrosoamine.

Step 4: Identify Compound Forming Oily Nitrosoamine

Given the characteristics and typical reactions of primary, secondary, and tertiary amines with aqueous nitrous acid, the compound that forms an oily nitrosoamine is the secondary amine diethylamine (c).

Key Concepts

Amines

Amines are organic compounds derived from ammonia (NH extsubscript{3}). They play a significant role in organic chemistry. Amines can be classified based on the number of carbon-containing groups attached to the nitrogen atom:

• Primary Amines: Have one alkyl or aryl group attached to the nitrogen ( extit{e.g.}, methylamine, ethylamine).
• Secondary Amines: Have two alkyl or aryl groups attached ( extit{e.g.}, diethylamine).
• Tertiary Amines: Have three alkyl or aryl groups attached ( extit{e.g.}, triethylamine).

Each class of amines has distinct chemical reactions and properties. This classification is important as it determines how the amines interact with other substances like nitrous acid. Amines are known for their characteristic ammonia-like smell and are widely used in the production of dyes, pharmaceuticals, and agrochemicals.

Nitrous Acid Reaction

The reaction of amines with nitrous acid ( ext{HNO}_2) leads to different outcomes depending on the amine type. Nitrous acid is typically generated in situ by mixing sodium nitrite (NaNO extsubscript{2}) with a mineral acid like hydrochloric acid.

• For primary amines, this reaction typically results in the formation of alcohol and nitrogen gas.
• In the case of secondary amines, such as diethylamine, the reaction produces nitrosoamines, which are oily liquid compounds.
• Tertiary amines generally do not react to form nitrosoamines.

Understanding these reaction pathways is crucial, especially in organic synthesis and safe handling, as some nitrosoamines are potentially carcinogenic.

Secondary Amines

Secondary amines contain two alkyl or aryl groups attached to the nitrogen atom. They differ from primary and tertiary amines in their reactivity and the types of reactions they undergo. When secondary amines such as diethylamine react with nitrous acid, they form nitrosoamines.
Secondary amines can be identified by their typical reaction pathway. The stability of secondary amines often makes them useful in a wide range of chemical reactions and industrial applications. Their ability to form stable nitrosoamines influences their use in biological and synthetic chemistry applications.

• Common examples include diethylamine and diphenylamine.
• Often used as intermediates in the synthesis of agrochemicals and dyes.

Diethylamine

Diethylamine is a secondary amine with the formula C extsubscript{4}H extsubscript{11}N. It consists of two ethyl groups attached to a central nitrogen atom. This structure is what makes it a secondary amine and distinguishes its reactions from primary and tertiary amines.
When diethylamine reacts with nitrous acid, it forms nitrosoamine, which appears as an oily liquid. This reaction is crucial in understanding its applications and implications.

• Diethylamine is commonly used as an intermediate in the production of rubber accelerators and pharmaceuticals.
• Its capability to form nitrosoamines also requires careful consideration due to the potential health impacts associated with these compounds.