Self -reaction of diazirinyl radicals in solution: A theoretical and experimental investigation regarding the mechanism for “prompt” no formation during hydrocarbon combustion
Abstract
The reaction CH(2Π) + N2 → HCN + N( 4S) has been proposed as the key step in the formation of “prompt” NO during hydrocarbon combustion, and diazirinyl radicals are believed to play a vital role in this transformation. This research investigates the bimolecular decomposition of diazirinyl radicals in solution to determine what role, if any, the “prompt” NO mechanism plays in this particular system. In the first study, computational methods were employed to explore the mechanism for bimolecular decomposition. Both N-N and C-N dimers were found to have low-energy transition states consistent with the observed products. In the second study, conditions were optimized for the thermal generation of 3-aryldiazirinyl radicals in solution. Under non-optimal conditions, formation of unknown species was observed. Separate reactions were run to determine their identity and origin. In the third study, a cross-over experiment was employed to determine the relative dimer contributions toward product formation, and the N-N dimer was found to be preferred by at least a factor of 100. The decomposition of 3-aryldiazirinyl radicals was further explored at increasing dilution to favor unimolecular decay. In all cases, no evidence for unimolecular decomposition (“prompt NO” mechanism) was observed suggesting that bimolecular decomposition is significantly more favorable even at low radical concentrations under our reaction conditions. Kinetic simulations were employed and suggest that the activation energy for “prompt NO” mechanism lies in the 17–22 kcal/mol range. An alternative step in the mechanism for “prompt” NO formation based on the bimolecular reaction of diazirinyl radicals with a neutral species, such as CO, is proposed. In a separate study, a series of isotopically distinct derivatizing agents were designed and synthesized for use in comparative proteomic studies.
Degree
Ph.D.
Advisors
Grutzner, Purdue University.
Subject Area
Organic chemistry|Chemistry
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.