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Related Concept Videos

Diazonium Group Substitution: –OH and –H01:19

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 Mechanism01:37

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.
Aryldiazonium Salts to Azo Dyes: Diazo Coupling01:11

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.
1° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Overview01:26

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...
Nucleophilic Aromatic Substitution of Aryldiazonium Salts: Aromatic SN101:14

Nucleophilic Aromatic Substitution of Aryldiazonium Salts: Aromatic SN1

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...
Aldehydes and Ketones with HCN: Cyanohydrin Formation Overview01:32

Aldehydes and Ketones with HCN: Cyanohydrin Formation Overview

Cyanohydrins are compounds that contain –CN and –OH groups on the same carbon atom. They are formed by the nucleophilic addition of the cyanide ions to the carbonyl group. Cyanide ions are highly basic and nucleophilic and can be generated from HCN under aqueous conditions. However, since HCN is a weak acid, the number of cyanide ions generated is very small. Hence, a small amount of base or KCN/NaCN is added to HCN to increase the concentration of the cyanide ions in the reaction mixture.

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Related Experiment Video

Updated: Jun 5, 2026

Continuous Flow Chemistry: Reaction of Diphenyldiazomethane with p-Nitrobenzoic Acid
07:06

Continuous Flow Chemistry: Reaction of Diphenyldiazomethane with p-Nitrobenzoic Acid

Published on: November 15, 2017

N'-(2,4-Dinitro-phen-yl)acetohydrazide.

Muhammad Zia-Ur-Rehman, Mark R J Elsegood, Shahid Mahmud

    Acta Crystallographica. Section E, Structure Reports Online
    |January 5, 2011
    PubMed
    Summary
    This summary is machine-generated.

    This study details the crystal structure of a nitro-substituted hydrazone compound. Molecular interactions, including hydrogen bonds and C-H...O interactions, form a complex three-dimensional network.

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    Area of Science:

    • Crystallography
    • Organic Chemistry
    • Supramolecular Chemistry

    Background:

    • Nitro-substituted hydrazones are important in medicinal chemistry and materials science.
    • Understanding molecular packing and intermolecular interactions is crucial for predicting material properties.

    Purpose of the Study:

    • To elucidate the crystal structure of a novel nitro-substituted hydrazone compound.
    • To analyze the types and strengths of intermolecular interactions present in the crystal lattice.

    Main Methods:

    • Single-crystal X-ray diffraction was employed to determine the molecular and crystal structure.
    • Analysis of bond lengths, bond angles, and intermolecular contacts was performed.

    Main Results:

    • The crystal structure of C(8)H(8)N(4)O(5) was determined, revealing specific conformations of nitro groups relative to the aromatic ring.
    • An intramolecular N-H⋯O hydrogen bond was identified between the hydrazide and ortho-nitro groups.
    • Strong intermolecular hydrogen bonds (C=O⋯H-N) formed chains, while weaker ONO⋯NO(2) and C-H⋯O-N interactions established a 3D network.

    Conclusions:

    • The study provides detailed insights into the solid-state structure of this nitro-substituted hydrazone.
    • The identified intermolecular interactions dictate the formation of a stable three-dimensional supramolecular architecture.