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Related Concept Videos

Basicity of Heterocyclic Aromatic Amines01:25

Basicity of Heterocyclic Aromatic Amines

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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).
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Mass Spectrometry of Amines01:19

Mass Spectrometry of Amines

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In mass spectroscopy, amines undergo fragmentation to give parent ions with odd molecule weights. This observed mass spectrum follows the nitrogen rule: a molecule with an odd number of nitrogen atoms produces a parent ion with an odd molecular weight. The remaining fragments have an even mass.
Amines undergo fragmentation through α cleavage, producing nitrogen-containing cations—iminium ions—and alkyl radicals. Mass spectra of aromatic and cyclic aliphatic amines exhibit...
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Structure of Amines01:19

Structure of Amines

2.7K
The hybridized nitrogen atom in amines possesses a lone pair of electrons and is bound to three substituents with a bond angle of around 108°, which is less than the tetrahedral angle of 109.5°. However, the C–N–H bond angle is slightly larger at 112°, with a carbon–nitrogen bond length of 147 pm. This carbon–nitrogen bond length of of amines is longer than the carbon–oxygen bond of alcohols (143 pm) but shorter than alkanes’...
2.7K
Preparation of Carboxylic Acids: Hydrolysis of Nitriles01:19

Preparation of Carboxylic Acids: Hydrolysis of Nitriles

4.7K
Nitriles (R–CN) can be converted into carboxylic acids (R–COOH) upon treatment with aqueous acids, i.e., upon hydrolysis of nitriles. Under base-catalyzed conditions, carboxylate anions (R–COO−) are formed.
4.7K
2° Amines to N-Nitrosamines: Reaction with NaNO201:20

2° Amines to N-Nitrosamines: Reaction with NaNO2

4.5K
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.
4.5K
Acid Halides to Amides: Aminolysis01:07

Acid Halides to Amides: Aminolysis

3.1K
Aminolysis is a nucleophilic acyl substitution reaction, where ammonia or amines act as nucleophiles to give the substitution product. Acid halides react with ammonia, primary amines, and secondary amines to yield primary, secondary, and tertiary amides, respectively.
In the first step of the aminolysis mechanism, the amine attacks the carbonyl carbon of the acyl chloride to form a tetrahedral intermediate. In the second step, the carbonyl group is re-formed with the elimination of a chloride...
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Measurement of the Potential Rates of Dissimilatory Nitrate Reduction to Ammonium Based on 14NH4+/15NH4+ Analyses via Sequential Conversion to N2O
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Measurement of the Potential Rates of Dissimilatory Nitrate Reduction to Ammonium Based on 14NH4+/15NH4+ Analyses via Sequential Conversion to N2O

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Matrix Isolation Study of Fumaric and Maleic Acids in Solid Nitrogen.

Timur Nikitin1, Susy Lopes1, Rui Fausto1

  • 1CQC-IMS, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal.

The Journal of Physical Chemistry. A
|June 23, 2022
PubMed
Summary
This summary is machine-generated.

Researchers used infrared spectroscopy and quantum chemical calculations to study fumaric and maleic acids. They discovered new, higher-energy conformers of these acids by using near-infrared light, revealing their stability in nitrogen matrices.

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Area of Science:

  • Physical Chemistry
  • Spectroscopy
  • Computational Chemistry

Background:

  • Fumaric acid (FA) and maleic acid (MA) are isomers with distinct chemical properties.
  • Understanding their conformational landscape is crucial for predicting reactivity and stability.
  • Previous studies have explored their properties, but high-energy conformers remain largely uncharacterized.

Purpose of the Study:

  • To experimentally and theoretically investigate the conformers of fumaric and maleic acids.
  • To generate and characterize novel, higher-energy conformers using selective near-infrared (NIR) excitation.
  • To determine the stability and lifetimes of these conformers in a nitrogen matrix.

Main Methods:

  • Experimental study using infrared spectroscopy in nitrogen matrices.
  • Theoretical calculations using Density Functional Theory (DFT) with B3LYP and Møller-Plesset perturbation theory (MP2).
  • Selective narrowband NIR excitation of OH stretching overtones to induce isomerization.

Main Results:

  • Quantum chemical calculations predicted numerous conformers for both FA and MA.
  • Two conformers of MA and three of FA were initially observed; NIR excitation generated novel high-energy conformers (VI and VII for MA, IV-VII for FA).
  • The nitrogen matrix stabilized these high-energy conformers, unlike argon matrices; UV irradiation induced isomerization and decarboxylation to acrylic acid.

Conclusions:

  • The study successfully generated and characterized previously unobserved high-energy conformers of fumaric and maleic acids.
  • Nitrogen matrices exhibit a significant stabilizing effect on these conformers due to specific interactions.
  • UV irradiation leads to C=C isomerization and decarboxylation, highlighting the photochemical reactivity of these acids.