Non-edible lignocellulosic biomass is of interest as a second-generation biofuel, showing potential as an alternative energy source that does not inhibit food supplies, though relatively little is known about its chemical properties. Monocyclic oxygenates such as tetrahydrofuran (THF) and tetrahydropyran (THP) have been explored as models for the larger lignocellulosic systems in computational studies. This work analyzes carbon-hydrogen bond dissociation enthalpies (BDEs, ?H298) in representative monocyclic oxygenated systems (THP, THF, cyclohexanone, and cyclopentanone), as well as in bicyclic systems derived from these species. This study also reports on a comprehensive examination of substituent effects (methyl, ethyl, isopropyl, and hydroxyl) for the monocyclic oxygenates. For instance, in unsubstituted THF, the C-H BDE was 391 kJ/mol at the 2-position, as calculated via the G3MP2B3 method; the corresponding BDEs were found to be 388 kJ/mol, 389 kJ/mol, and 390 kJ/mol for the 2-positions of 2-methyl tetrahydrofuran, 2-ethyl tetrahydrofuran, and 2-isopropyl tetrahydrofuran. Preliminary results suggest that increasing complexity from monocyclic oxygenated systems to alkyl-substituted or bicyclic derivatives of these systems has little effect on BDE, but the presence of a functional group does affect BDE. All Gaussian09 calculations were run via the Ohio Supercomputer Center.

Exploring the thermochemistry of monocyclic and bicyclic oxygenated species via computational chemistry methods

247th National Meeting (2014)

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