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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...

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.

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.

Electrophilic Aromatic Substitution: Nitration of Benzene

Electrophilic Aromatic Substitution: Nitration of Benzene

The nitration of benzene is an example of an electrophilic aromatic substitution reaction. It involves the formation of a very powerful electrophile, the nitronium ion, which is linear in shape. The reaction occurs through the interaction of two strong acids, sulfuric and nitric acid.

Preparation of Amines: Reduction of Oximes and Nitro Compounds

Preparation of Amines: Reduction of Oximes and Nitro Compounds

Oximes can be reduced to primary amines using catalytic hydrogenation, hydride reduction, or sodium metal reduction. The reduction of aliphatic and aromatic nitro compounds to primary amines takes place by either catalytic hydrogenation or by using active metals like Fe, Zn, and Sn in the presence of an acid.
Though catalytic hydrogenation can reduce nitrobenzenes, the reduction is nonselective in the presence of other functional groups. For instance, if nitrobenzene contains an aldehyde group,...

Nitrosation of Enols

Nitrosation of Enols

The nitrosation reaction is one of the methods of preparing 1,2-diketones. The enol tautomer of the starting ketone reacts with sodium nitrite in hydrochloric acid, generating the 1,2-diketone after hydrolysis.

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Related Experiment Video

Updated: May 13, 2026

A Direct, Regioselective and Atom-Economical Synthesis of 3-Aroyl-N-hydroxy-5-nitroindoles by Cycloaddition of 4-Nitronitrosobenzene with Alkynones

A Direct, Regioselective and Atom-Economical Synthesis of 3-Aroyl-N-hydroxy-5-nitroindoles by Cycloaddition of 4-Nitronitrosobenzene with Alkynones

Published on: January 21, 2020

4-Meth-oxy-benzamidinium nitrate.

Simona Irrera¹, Gustavo Portalone

¹Chemistry Department, 'Sapienza' University of Rome, P.le A. Moro, 5, I-00185 Rome, Italy.

Acta Crystallographica. Section E, Structure Reports Online

|March 12, 2013

Summary

Researchers synthesized a novel salt from 4-methoxy-benzamidine and nitric acid. Crystal structure analysis revealed a non-planar ion pair linked by hydrogen bonds into a 3D network.

Area of Science:

Crystallography
Organic Chemistry
Materials Science

Background:

Benzamidine derivatives are important in medicinal chemistry and materials science.
Understanding the crystal packing and intermolecular interactions of organic salts is crucial for designing new materials.

Purpose of the Study:

To synthesize and characterize a novel salt of 4-methoxy-benzamidine.
To elucidate the crystal structure and hydrogen bonding network of the synthesized salt.

Main Methods:

Synthesis of the title salt via reaction of 4-methoxy-benzamidine with nitric acid.
Single-crystal X-ray diffraction analysis to determine the crystal structure.
Analysis of bond lengths, bond angles, and dihedral angles to describe molecular geometry and ion pairing.

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Published on: January 19, 2016

Main Results:

The title salt, C8H11N2O(+)·NO3(-), was successfully synthesized.
The asymmetric unit contains a non-planar 4-methoxy-benzamidinium cation and a nitrate anion.
The cation and anion form a non-planar ion pair with a dihedral angle of 19.28(6)°.
A three-dimensional network is formed through N-H⋯O hydrogen bonds between the ionic components.

Conclusions:

The study successfully synthesized and characterized a new organic salt.
The crystal structure reveals a non-planar ion pair and a robust 3D hydrogen-bonded network.
The findings contribute to the understanding of crystal engineering with amidinium salts.