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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.

Carboxylic Acids to Methylesters: Alkylation using Diazomethane

Carboxylic Acids to Methylesters: Alkylation using Diazomethane

Carboxylic acids react with diazomethane in an ether solvent via alkylation at the carboxylate oxygen atom to give methyl esters of the corresponding acid with excellent yields.

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.

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.

Diazonium Group Substitution with Halogens and Cyanide: Sandmeyer and Schiemann Reactions

Diazonium Group Substitution with Halogens and Cyanide: Sandmeyer and Schiemann Reactions

Arenediazonium substitution reactions occur when the diazonium group is substituted by various functional groups such as halides, hydroxyl, nitrile, etc. For instance, arenediazonium salts react with copper(I) salts of chloride, bromide, or cyanide to form corresponding aryl chlorides, bromides, and nitriles. These reactions are named Sandmeyer reactions. Although the mechanism of this reaction is complicated, as illustrated in Figure 1, they are believed to progress via an aryl copper...

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(2,4-Dinitro-phen-yl)(1-methyl-1-nitro-ethyl)diazene.

¹Department of Chemistry and Chemical Engineering, Baoji College of Arts and Sciences, Baoji 721007, People's Republic of China.

Acta Crystallographica. Section E, Structure Reports Online

|May 18, 2011

Summary

The crystal structure of a novel azo compound, C(9)H(9)N(5)O(6), reveals a trans conformation of the azo group. This structural analysis provides insights into the spatial arrangement of nitro groups relative to the benzene ring.

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Area of Science:

Crystallography
Organic Chemistry
Molecular Structure

Background:

Understanding the molecular geometry of organic compounds is crucial for predicting their properties and reactivity.
Azo compounds are a significant class of organic molecules with diverse applications.

Purpose of the Study:

To determine the precise three-dimensional structure of the title compound, C(9)H(9)N(5)O(6).
To analyze the conformation of the azo group and the orientation of the nitro substituents within the crystal lattice.

Main Methods:

Single-crystal X-ray diffraction was employed to elucidate the molecular structure.
Crystallographic data were collected and analyzed to determine bond lengths, bond angles, and dihedral angles.

Main Results:

The crystal structure confirmed the molecular formula C(9)H(9)N(5)O(6).
The azo group was found to adopt a trans conformation.
Dihedral angles between the nitro groups and the benzene ring were measured as 11.6(3)° and 21.3(3)°.

Conclusions:

The study provides a detailed structural characterization of the title azo compound.
The observed conformation and dihedral angles offer valuable data for computational modeling and structure-property relationship studies in related azo compounds.