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
Summary
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.
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.
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