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1° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Overview

1° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO₂ Overview

Nitrous acid and nitric acids are two types of acids containing nitrogen, among which nitrous acid is weaker than nitric acid. Nitrous acid with a pKa value of 3.37 ionizes in water to give a nitrite ion and the hydronium ion.
The nitrous acid is unstable. Hence, it is formed in situ from a solution of sodium nitrite and cold aqueous acids such as hydrochloric or sulfuric acid. In an acidic solution, the –OH group of nitrous acid undergoes protonation to give oxonium ion, followed by water loss...

1° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Mechanism

1° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO₂ Mechanism

Nitrous acid is a relatively weak and unstable acid prepared in situ by the reaction of sodium nitrite and cold, dilute hydrochloric acid. In an acidic solution, the nitrous acid undergoes protonation when it loses water to form a nitrosonium ion—an electrophile. Nitrous acid reacts with primary amines to give diazonium salts. The reaction is called diazotization of primary amines.

2° Amines to N-Nitrosamines: Reaction with NaNO2

2° Amines to N-Nitrosamines: Reaction with NaNO₂

Secondary amines react with nitrous acid to form N-nitrosamines, as depicted in Figure 1. Nitrous acid, a weak and unstable acid, is formed in situ from an aqueous solution of sodium nitrite and strong acids, such as hydrochloric acid or sulfuric acid, in cold conditions. In the presence of an acid, the nitrous acid gets protonated. The subsequent loss of water results in the formation of the electrophile known as nitrosonium ion.

Structure of Amines

Structure of Amines

The hybridized nitrogen atom in amines possesses a lone pair of electrons and is bound to three substituents with a bond angle of around 108°, which is less than the tetrahedral angle of 109.5°. However, the C–N–H bond angle is slightly larger at 112°, with a carbon–nitrogen bond length of 147 pm. This carbon–nitrogen bond length of of amines is longer than the carbon–oxygen bond of alcohols (143 pm) but shorter than alkanes’ carbon–carbon bond (154 pm). These aspects are illustrated in Figure...

Diazonium Group Substitution: –OH and –H

Diazonium Group Substitution: –OH and –H

Nitrous acid, a weak acid, is prepared in situ via the reaction of sodium nitrite with a strong acid under cold conditions. This nitrous acid prepared in situ reacts with primary arylamines to form arenediazonium salts. Such reactions are known as diazotization reactions. As shown in Figure 1, the formation of arenediazonium salts begins with the decomposition of nitrous acid in an acidic solution to give nitrosonium ions.

Nomenclature of Secondary and Tertiary Amines

Nomenclature of Secondary and Tertiary Amines

The secondary and tertiary amines are derivatives of ammonia, where two and three of its hydrogens are replaced by alkyl groups, respectively. Secondary and tertiary amines can be symmetrical with identical alkyl groups attached to the nitrogen atom or unsymmetrical when more than one type of alkyl group is present. The standard nomenclature of secondary and tertiary amines is similar to the names given to the primary amines. They are generally named alkylamines. As depicted in Figure 1, for...

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Updated: Jun 1, 2026

One-pot Microwave-assisted Conversion of Anomeric Nitrate-esters to Trichloroacetimidates

One-pot Microwave-assisted Conversion of Anomeric Nitrate-esters to Trichloroacetimidates

Published on: January 15, 2018

2-Amino-pyrimidinium nitrate.

Xiao-Li Cheng, Shan Gao, Seik Weng Ng

Acta Crystallographica. Section E, Structure Reports Online

|May 18, 2011

Summary

The crystal structure of a novel compound reveals coplanar ions linked by hydrogen bonds. These ion pairs further assemble into linear chains within the crystal lattice, showcasing unique molecular assembly.

Area of Science:

Crystallography
Supramolecular Chemistry

Background:

Understanding the self-assembly of organic salts is crucial for materials science.
Hydrogen bonding plays a key role in directing crystal packing and network formation.

Purpose of the Study:

To elucidate the crystal structure and intermolecular interactions of the title compound, C(4)H(6)N(3) (+)·NO(3) (-).
To investigate the role of hydrogen bonding in the formation of ion pairs and extended crystal networks.

Main Methods:

Single-crystal X-ray diffraction analysis was employed to determine the three-dimensional structure.
Analysis of hydrogen bonding (N-H⋯O) and crystal packing was performed.

Main Results:

The cation (C(4)H(6)N(3) (+)) and anion (NO(3) (-)) were found to be coplanar with a root-mean-square deviation of 0.048 Å.

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Last Updated: Jun 1, 2026

One-pot Microwave-assisted Conversion of Anomeric Nitrate-esters to Trichloroacetimidates

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Published on: January 15, 2018

Synthesis of Information-bearing Peptoids and their Sequence-directed Dynamic Covalent Self-assembly

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Nitropeptide Profiling and Identification Illustrated by Angiotensin II

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A hydrogen bond between the cation and anion forms an ion pair.

Adjacent ion pairs are linked by additional N-H⋯O hydrogen bonds, forming linear chains along the b axis.

Conclusions:

The title compound forms a well-defined crystal structure driven by ionic interactions and hydrogen bonding.
The observed linear chain assembly highlights the directional nature of hydrogen bonds in supramolecular construction.