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Related Concept Videos

Basicity of Heterocyclic Aromatic Amines01:25

Basicity of Heterocyclic Aromatic Amines

Heterocyclic amines, where the N atom is a part of an alicyclic system, are similar in basicity to alkylamines. Interestingly, the heterocyclic amine having a nitrogen atom as part of an aromatic ring has much less basicity than its corresponding alicyclic counterpart. For this reason, as presented in Figure 1, piperidine (pKb = 2.8) is significantly more basic than pyridine (pKb = 8.8).
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.
meta-Directing Deactivators: –NO2, –CN, –CHO, –⁠CO2R, –COR, –CO2H01:13

meta-Directing Deactivators: –NO2, –CN, –CHO, –⁠CO2R, –COR, –CO2H

All meta-directing substituents are deactivating groups. These substituents withdraw electrons from the aromatic ring, making the ring less reactive toward electrophilic substitution. For example, the nitration of nitrobenzene is 100,000 times slower than that of benzene because of the deactivating effect of the nitro group. The first step in an electrophilic aromatic substitution is the addition of an electrophile to form a resonance-stabilized carbocation. The energy diagrams for the...
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 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...
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.

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Related Experiment Video

Updated: May 30, 2026

Syntheses, Crystallization, and Spectroscopic Characterization of 3,5-Lutidine N-Oxide Dehydrate
06:18

Syntheses, Crystallization, and Spectroscopic Characterization of 3,5-Lutidine N-Oxide Dehydrate

Published on: April 24, 2018

2,6-Dichloro-3-nitro-pyridine.

Hoong-Kun Fun, Suhana Arshad, B Chandrakantha

    Acta Crystallographica. Section E, Structure Reports Online
    |August 13, 2011
    PubMed
    Summary
    This summary is machine-generated.

    This study details the crystal structure of C(5)H(2)Cl(2)N(2)O(2), revealing two independent molecules with planar pyridine rings. Analysis identified short intermolecular chlorine-oxygen and chlorine-chlorine contacts, with no significant overall interactions in the crystal packing.

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    A General Method for Detecting Nitrosamide Formation in the In Vitro Metabolism of Nitrosamines by Cytochrome P450s
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    A General Method for Detecting Nitrosamide Formation in the In Vitro Metabolism of Nitrosamines by Cytochrome P450s

    Published on: September 25, 2017

    Area of Science:

    • Crystallography
    • Chemical Physics
    • Materials Science

    Background:

    • Understanding the molecular arrangement and intermolecular forces in crystalline solids is crucial for predicting material properties.
    • The specific compound C(5)H(2)Cl(2)N(2)O(2) has not been extensively studied regarding its solid-state structure.

    Purpose of the Study:

    • To elucidate the crystal structure of the title compound, C(5)H(2)Cl(2)N(2)O(2).
    • To identify and analyze any significant intermolecular interactions present in the crystal lattice.

    Main Methods:

    • Single-crystal X-ray diffraction was employed to determine the unit cell and atomic positions.
    • Crystallographic analysis was performed to assess molecular geometry and intermolecular contacts.

    Main Results:

    • The asymmetric unit contains two crystallographically independent molecules of C(5)H(2)Cl(2)N(2)O(2).
    • The pyridine ring within each molecule exhibits near-planarity.
    • Short chlorine-oxygen (Cl⋯O) and chlorine-chlorine (Cl⋯Cl) contacts were observed, measuring 3.09–3.13 Å and 3.38 Å, respectively.
    • No significant intermolecular interactions were detected in the overall crystal packing.

    Conclusions:

    • The crystal structure of C(5)H(2)Cl(2)N(2)O(2) is characterized by the presence of two independent molecules and specific short-range contacts.
    • The limited intermolecular interactions suggest that crystal packing is primarily influenced by these localized contacts rather than extended networks.