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Proton affinity of methyl peroxynitrate.
Rose M Ravelo1, Joseph S Francisco
1Departments of Chemistry and Earth and Atmospheric Science, Purdue University, West Lafayette, Indiana 47907, USA.
The Journal of Physical Chemistry. A
|December 14, 2007
Summary
Researchers studied methyl peroxynitrate and its protonated form using advanced computational methods. The study determined the stable structure and proton affinity of methyl peroxynitrate, offering insights into peroxynitrate chemistry.
Area of Science:
- Computational Chemistry
- Quantum Chemistry
- Atmospheric Chemistry
Background:
- Methyl peroxynitrate (CH3O3NO2) is an important atmospheric compound.
- Understanding its properties, especially when protonated, is crucial for atmospheric modeling.
- Protonation can significantly alter the reactivity and stability of molecules.
Purpose of the Study:
- To investigate the equilibrium structures and vibrational frequencies of methyl peroxynitrate.
- To determine the stable structures of protonated methyl peroxynitrate.
- To calculate the proton affinity of methyl peroxynitrate.
Main Methods:
- Employed ab initio computational methods, including Quadratic Configuration Interaction with Singles and Doubles (QCISD).
- Utilized the QCISD(T) method to incorporate corrections for triple excitations.
- Calculated equilibrium structures, harmonic vibrational frequencies, and binding energies.
Main Results:
- Identified the lowest-energy gas-phase structure of protonated methyl peroxynitrate as a complex between CH3OOH and NO2+.
- The CH3OOH.NO2+ complex is found to be bound by 22 +/- 2 kcal/mol.
- The estimated proton affinity of methyl peroxynitrate is 178.8 +/- 3 kcal/mol.
Conclusions:
- The study provides accurate structural and energetic data for methyl peroxynitrate and its protonated form.
- The calculated proton affinity offers valuable data for understanding the behavior of peroxynitrates in various chemical environments.
- A general trend for the proton affinity of ROO-NO2 compounds is discussed, contributing to broader chemical insights.
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