Theoretical study on the unimolecular decomposition of proline

As a representative model compound for cyclic amino acids in biomass, initial reactions in the decomposition of proline are thoroughly investigated herein. The weakest bond in the proline molecule is found to be the H atom gem to the carboxylic group with a bond dissociation enthalpy of 75.0 kcal/mol. Carboxylation and dehydration channels are found to incur enthalpies of activations at 71.0 kcal/mol and 72.8 kcal/mol; respectively. Calculated pressure-dependent reaction rate constants, i.e.; k (P, T) values, indicates that water elimination and H elimination from the carbon bearing the carboxylic group dominates the unimolecular decomposition of proline at all temperatures and pressures.