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Related Concept Videos

1° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Mechanism01:37

1° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Mechanism

4.6K
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.
4.6K
1° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Overview01:26

1° Amines to Diazonium or Aryldiazonium Salts: Diazotization with NaNO2 Overview

3.8K
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...
3.8K
Diazonium Group Substitution: –OH and –H01:19

Diazonium Group Substitution: –OH and –H

3.2K
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.
3.2K
2° Amines to N-Nitrosamines: Reaction with NaNO201:20

2° Amines to N-Nitrosamines: Reaction with NaNO2

5.2K
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.
5.2K

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Chemiluminescence-based Assays for Detection of Nitric Oxide and its Derivatives from Autoxidation and Nitrosated Compounds
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Using Diazotization Reaction to Develop Portable Liquid-Crystal-Based Sensors for Nitrite Detection.

Tsung Yang Ho1, Yi-Hsuan Lan1, Jhih-Wei Huang1

  • 1Department of Chemistry, Tamkang University, New Taipei City 25137, Taiwan.

ACS Omega
|June 2, 2020
PubMed
Summary

A novel liquid-crystal sensor detects nitrite in water using a diazotization reaction. The sensor shows a bright-to-dark transition, offering a portable and selective method for environmental monitoring.

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Area of Science:

  • Analytical Chemistry
  • Materials Science
  • Environmental Science

Background:

  • Nitrite detection is crucial for environmental and health monitoring.
  • Existing methods for nitrite detection can be complex and require specialized equipment.
  • Liquid crystals (LCs) offer unique optical properties that can be exploited for sensing applications.

Purpose of the Study:

  • To develop a novel liquid-crystal-based sensor for the detection of nitrite in aqueous solutions.
  • To utilize a diazotization reaction as the sensing mechanism for nitrite detection.
  • To create a portable and selective nitrite detection system.

Main Methods:

  • Synthesized tetradecyl 4-aminobenzoate (14CBA) and doped it into a nematic liquid crystal (4-cyano-4'-pentylbiphenyl, 5CB).
  • Utilized the diazotization reaction between nitrite and alkylanilines to induce a change in LC orientation.
  • Observed the bright-to-dark transition of the LC image under a microscope.
  • Validated the system using environmental water samples (tap water, pond water).
  • Demonstrated smartphone integration for optical signal measurement.

Main Results:

  • The developed LC sensor exhibited a clear bright-to-dark optical transition upon exposure to nitrite.
  • The limit of detection (LOD) for nitrite was determined to be 25 μM.
  • The sensor demonstrated high selectivity for nitrite detection.
  • The system successfully detected nitrite in environmental water samples.
  • Smartphone-based optical signal measurement confirmed the system's portability.

Conclusions:

  • A sensitive and selective liquid-crystal-based sensor for nitrite detection has been successfully developed.
  • The sensor leverages a simple diazotization reaction and observable optical changes.
  • The integration with smartphone technology highlights the potential for on-site, portable nitrite analysis in various water samples.