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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.

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...

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.

Aryldiazonium Salts to Azo Dyes: Diazo Coupling

Aryldiazonium Salts to Azo Dyes: Diazo Coupling

The reaction of weakly electrophilic aryldiazonium (also called arenediazonium) salts with highly activated aromatic compounds leads to the formation of products with an —N=N— link, called an azo linkage. This reaction, presented in Figure 1, is known as diazo coupling and occurs without the loss of the nitrogen atoms of the aryldiazonium salt. Highly activated aromatic compounds such as phenols or arylamines favor the diazo coupling reaction. The coupling generally occurs at the para position.

Nucleophilic Aromatic Substitution of Aryldiazonium Salts: Aromatic SN1

Nucleophilic Aromatic Substitution of Aryldiazonium Salts: Aromatic S_N1

Treating arylamines with nitrous acid gives aryldiazonium salts that are effective substrates in nucleophilic aromatic substitution reactions. The diazonio group in these salts can be easily displaced by different nucleophiles, yielding a wide variety of substituted benzenes. The leaving group departs as nitrogen gas, and this easy elimination is the driving force for the substitution reaction.
In the Sandmeyer reaction, for example, the diazonio group is replaced by a chloro, bromo, or cyano...

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3-Nitro-1H-1,2,4-triazole.

Madhukar Hemamalini¹, Hoong-Kun Fun

¹X-ray Crystallography Unit, School of Physics, Universiti Sains Malaysia, 11800 USM, Penang, Malaysia.

Acta Crystallographica. Section E, Structure Reports Online

|April 28, 2011

Summary

This summary is machine-generated.

This study details the crystal structure of a compound containing two planar 1H-1,2,4-triazole rings. Molecules form chains through hydrogen bonds, revealing insights into molecular arrangement and intermolecular interactions.

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Area of Science:

Crystallography
Chemical Physics
Materials Science

Background:

Understanding the three-dimensional arrangement of atoms in molecules is crucial for predicting their properties and reactivity.
Crystal structure analysis provides fundamental insights into intermolecular forces and solid-state behavior.

Purpose of the Study:

To elucidate the crystal structure of the title compound, C(2)H(2)N(4)O(2).
To analyze the planarity of the triazole rings and the dihedral angle between them.
To investigate the intermolecular interactions and supramolecular assembly in the crystalline state.

Main Methods:

Single-crystal X-ray diffraction was employed to determine the molecular and crystal structure.
Analysis of bond lengths, bond angles, and torsion angles provided information on molecular geometry.
Intermolecular interactions, including hydrogen bonds, were identified and characterized.

Main Results:

The asymmetric unit contains two independent molecules of C(2)H(2)N(4)O(2).
The 1H-1,2,4-triazole rings within each molecule are nearly planar, with minimal deviations.
A dihedral angle of 56.58° was observed between the two triazole rings.
The crystal structure is characterized by intermolecular N-H⋯N and C-H⋯O hydrogen bonds, forming a supramolecular chain along the b-axis.

Conclusions:

The study successfully determined the crystal structure of C(2)H(2)N(4)O(2), highlighting the planarity of its triazole rings.
The identified hydrogen bonding network dictates the formation of a one-dimensional supramolecular chain.
These findings contribute to the understanding of structure-property relationships in related heterocyclic compounds.