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Related Concept Videos

2° Amines to N-Nitrosamines: Reaction with NaNO201:20

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.
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.
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...
ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH301:11

ortho–para-Directing Activators: –CH3, –OH, –⁠NH2, –OCH3

All ortho–para directors, excluding halogens, are activating groups. These groups donate electrons to the ring, making the ring carbons electron-rich. Consequently, the reactivity of the aromatic ring towards electrophilic substitution increases. For instance, the nitration of anisole is about 10,000 times faster than the nitration of benzene. The electron-donating effect of the methoxy group in anisole activates the ortho and para positions on the ring and stabilizes the corresponding...
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.
Nitrosation of Enols01:19

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 22, 2026

A Direct, Regioselective and Atom-Economical Synthesis of 3-Aroyl-N-hydroxy-5-nitroindoles by Cycloaddition of 4-Nitronitrosobenzene with Alkynones
07:30

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

2,4-Diiodo-3-nitro-anisole.

Xianfei Li, Lei Cao, Chuansheng Ruan

    Acta Crystallographica. Section E, Structure Reports Online
    |May 17, 2012
    PubMed
    Summary

    This study details the crystal structure of 1,3-diiodo-4-methoxy-2-nitrobenzene. Key findings include the near-perpendicular orientation of the nitro group and aromatic π-π stacking interactions in the solid state.

    Area of Science:

    • Crystallography
    • Organic Chemistry
    • Supramolecular Chemistry

    Background:

    • Understanding molecular packing and intermolecular interactions is crucial for predicting material properties.
    • Aromatic compounds with nitro and iodo substituents exhibit diverse solid-state behaviors.

    Purpose of the Study:

    • To elucidate the crystal structure and intermolecular interactions of 1,3-diiodo-4-methoxy-2-nitrobenzene.
    • To investigate the influence of substituents on molecular conformation and crystal packing.

    Main Methods:

    • Single-crystal X-ray diffraction analysis was employed to determine the three-dimensional structure.
    • Analysis of crystallographic data to identify and quantify intermolecular interactions.

    Main Results:

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    Chemoselective Preparation of 1-Iodoalkynes, 1,2-Diiodoalkenes, and 1,1,2-Triiodoalkenes Based on the Oxidative Iodination of Terminal Alkynes
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    Chemoselective Preparation of 1-Iodoalkynes, 1,2-Diiodoalkenes, and 1,1,2-Triiodoalkenes Based on the Oxidative Iodination of Terminal Alkynes

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

    Synthesis and Purification of Iodoaziridines Involving Quantitative Selection of the Optimal Stationary Phase for Chromatography
    10:14

    Synthesis and Purification of Iodoaziridines Involving Quantitative Selection of the Optimal Stationary Phase for Chromatography

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    Chemoselective Preparation of 1-Iodoalkynes, 1,2-Diiodoalkenes, and 1,1,2-Triiodoalkenes Based on the Oxidative Iodination of Terminal Alkynes
    09:54

    Chemoselective Preparation of 1-Iodoalkynes, 1,2-Diiodoalkenes, and 1,1,2-Triiodoalkenes Based on the Oxidative Iodination of Terminal Alkynes

    Published on: September 12, 2018

    • The dihedral angle between the benzene ring and the nitro group is 88.0°.
    • The methyl group is nearly coplanar with the benzene ring (deviation = 0.034 Å).
    • Aromatic π-π stacking was observed between inversion-related rings with a centroid-centroid separation of 3.865 Å.
    • A weak C-I⋯π interaction was identified (I⋯π distance = 3.701 Å).

    Conclusions:

    • The crystal structure of 1,3-diiodo-4-methoxy-2-nitrobenzene is characterized by a near-orthogonal nitro group and significant π-π stacking.
    • Weak C-I⋯π interactions may play a role in stabilizing the crystal lattice.
    • No significant intermolecular I⋯I contacts were found.