The kinetics and mechanisms of methyl 2‐bromopropionate and 2‐bromopropionic acid pyrolyses under maximum inhibition

The kinetics of the gas phase pyrolyses of methyl 2‐bromopropionate and 2‐bromopropionic acid were studied in a seasoned, static reaction vessel and under maximum inhibition of the free radical suppressor toluene. The working temperature and pressure range was 310–430°C and 26.5–201.5 torr, respectively. The reactions proved to be homogeneous, unimolecular, and obeys a first‐order rate law. The rate coefficients are expressible by the following equations: for methyl 2‐bromopropionate, log k 1 (s −1 ) = (13.10 ± 0.34) − (211.4 ± 4.4)kJ mol −1 (2.303 RT ) −1 ; for 2‐bromopropionic acid, log k 1 (s −1 ) = (12.41 ± 0.29) − (180.3 ± 3.4)kJ mol −1 (2.303 RT ) −1 . The bromoacid yields acetaldehyde, CO and HBr. Because of this result, the mechanism is believed to proceed via a polar five‐membered cyclic transition state.