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Electrophilic Aromatic Substitution: Nitration of Benzene

Electrophilic Aromatic Substitution: Nitration of Benzene

The nitration of benzene is an example of an electrophilic aromatic substitution reaction. It involves the formation of a very powerful electrophile, the nitronium ion, which is linear in shape. The reaction occurs through the interaction of two strong acids, sulfuric and nitric acid.

Nucleophilic Aromatic Substitution: Addition–Elimination (SNAr)

Nucleophilic Aromatic Substitution: Addition–Elimination (S_NAr)

Nucleophilic substitution in aromatic compounds is feasible in substrates bearing strong electron-withdrawing substituents positioned ortho or para to the leaving group. The reaction proceeds via two steps: the addition of the nucleophile and the elimination of the leaving group.
The reaction begins with an attack of the nucleophile on the carbon that holds the leaving group. This results in the delocalization of the π electrons over the ring carbons. The resonance interaction between...

2° Amines to N-Nitrosamines: Reaction with NaNO2

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.

NMR Spectroscopy of Aromatic Compounds

NMR Spectroscopy of Aromatic Compounds

Aromatic compounds can be identified or analyzed using proton NMR and carbon‐13 NMR. Typically, aromatic hydrogens or hydrogens directly bonded to the aromatic rings are strongly deshielded by the aromatic ring current. Therefore, they absorb in the range of 6.5–8.0 ppm in proton NMR spectra. For instance, aromatic hydrogens directly bonded to the benzene ring absorb at 7.3 ppm. However, aromatic hydrogens of larger rings absorb farther upfield or downfield than the ideal range.

Insensitive Nuclei Enhanced by Polarization Transfer (INEPT)

Insensitive Nuclei Enhanced by Polarization Transfer (INEPT)

Insensitive Nuclei Enhanced by Polarization Transfer (INEPT) is an advanced Nuclear Magnetic Resonance (NMR) technique specifically designed to detect and enhance the signals of low-abundance nuclei, such as carbon-13 and nitrogen-15, in small molecules. The fundamental principle behind INEPT is the transfer of polarization from a more abundant and highly polarizable nucleus, typically hydrogen-1, to the low-abundance nucleus of interest. This process effectively boosts the NMR signal of the...

NMR Spectroscopy Of Amines

NMR Spectroscopy Of Amines

In proton NMR spectroscopy, primary amines and secondary amines showcase their N–H protons as a broad signal in the chemical shift range between δ 0.5 and 5 ppm. The exact position in this range depends on several factors, including sample concentration, hydrogen bonding, and the type of solvent used. Since amine protons undergo fast proton exchange in solution, the protons are labile and therefore do not participate in any splitting with adjacent protons. Thus, the observed peak is...

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Updated: Jul 15, 2025

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

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

Published on: September 25, 2017

Aromatic nitrogen scanning by ipso-selective nitrene internalization.

Tyler J Pearson¹, Ryoma Shimazumi¹, Julia L Driscoll¹

¹Department of Chemistry, University of Chicago, Chicago, IL 60637, USA.

Science (New York, N.Y.)

|September 28, 2023

Summary

This summary is machine-generated.

Researchers developed a new method for direct carbon-to-nitrogen replacement in aryl compounds, enabling efficient synthesis of pyridine isomers for drug discovery. This streamlined process simplifies the creation of diverse molecular structures.

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Rapid Scan Electron Paramagnetic Resonance Opens New Avenues for Imaging Physiologically Important Parameters In Vivo

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Published on: September 26, 2016

Area of Science:

Organic Chemistry
Medicinal Chemistry
Synthetic Methodology

Background:

Nitrogen scanning in aryl fragments is crucial for drug discovery.
Current methods necessitate lengthy, parallel synthesis of pyridyl isomers.
A lack of direct carbon-to-nitrogen (C-to-N) replacement reactions limits efficiency.

Purpose of the Study:

To develop a site-directable aryl C-to-N replacement reaction.
To enable unified access to various pyridine isomers.
To streamline the drug discovery process by simplifying synthesis.

Main Methods:

A two-step, one-pot procedure involving aryl azides.
Photochemical conversion of aryl azides to 3H-azepines.
Oxidatively triggered C2-selective cheletropic carbon extrusion via a spirocyclic azanorcaradiene intermediate.

Main Results:

Successful regioselective synthesis of pyridine products.
The reaction proceeds without perturbing the substrate due to ipso-carbon excision.
Demonstrated application in the synthesis of a pyridyl estrone derivative and a nitrogen scan.

Conclusions:

The reported nitrene-internalization process provides a novel C-to-N replacement strategy.
This method offers a more efficient and unified approach to synthesizing diverse pyridine isomers.
The reaction's site-directability and regioselectivity are advantageous for medicinal chemistry applications.