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J Phys Chem A

Title:		Hydroxyalkoxy radicals: importance of intramolecular hydrogen bonding on chain branching reactions in the combustion and atmospheric decomposition of hydrocarbons
Author(s):		Davis AC; Francisco JS;
Address:		"Department of Chemistry and Department of Earth and Atmospheric Science, Purdue University , West Lafayette, Indiana 47907-1393, United States"
Journal Title:		J Phys Chem A
Year:		2014
Volume:		20141107
Issue:		46
Page Number:		10982 - 11001
DOI:		10.1021/jp506436g
ISSN/ISBN:		1520-5215 (Electronic) 1089-5639 (Linking)
Abstract:		"During both the atmospheric oxidation and combustion of volatile organic compounds, sequential addition of oxygen can lead to compounds that contain multiple hydrogen-bonding sites. The presence of two or more of these sites on a hydrocarbon introduces the possibility of intramolecular H-bonding, which can have a stabilizing effect on the reactants, products, and transition states of subsequent reactions. The present work compares the absolute energies of two sets of conformations, those that contain intramolecular H-bonds and those that lack intramolecular H-bonds, for each reactant, product, and transition state species in the 1,2 through 1,7 H-migrations and Calpha-Cbeta, Calpha-H, and Calpha-OH-bond scission reactions in the n-hydroxyeth-1-oxy through n-hydroxyhex-1-oxy radicals, for n ranging from 1 to 6. The difference in energy between the two conformations represents the balance between the stabilizing effects of H-bonds and the steric cost of bringing the two H-bonding sites together. The effect of intramolecular H-bonding and the OH group is assessed by comparing the net intramolecular H-bond stabilization energies, the reaction enthalpies, and barrier heights of the n-hydroxyalkoxy radical reactions with the corresponding alkoxy radicals values. The results suggest that there is a complex dependence on the location of the two H-bonding groups, the location of the abstraction or bond scission, and the shape of the transition state that dictates the extent to which intramolecular H-bonding effects the relative importance of H-migration and bond scission reactions for each n-hydroxyalkoxy radical. These findings have important implications for future studies on hydrocarbons with multiple H-bonding sites"
Keywords:
Notes:		"PubMed-not-MEDLINEDavis, Alexander C Francisco, Joseph S eng 2014/10/28 J Phys Chem A. 2014 Nov 20; 118(46):10982-1001. doi: 10.1021/jp506436g. Epub 2014 Nov 7"