The nature of the transition state in amides pyrolysis. The rates of pyrolysis of N-benzoyl and N-acetylpropanamide,N-benzoyl and N-acetyl-2-methylpropanamide,and N-thioacetylpropanamide

The rates of gas-phase elimination reactions of N-benzoyl and N-acetyl-propanamide and N-benzoyl and N-acetyl-2-methylpropanamide are measured and discussed. They undergo unimolecular first-order elimination reactions. The reactivities of N-benzoylamides have been compared with each other and with those of N-acetylamides. The kinetic data together with the product analysis reveals that, the statistical factor of the availability of β-hydrogen atoms for elimination as well as steric factor are obscured by polar factor in gas-phase elimination reactions of N-benzoylamides while the statistical factor rather than electronic effect operates in each of N-acetylamides. © 1995 John Wiley & Sons, Inc.