Theoretical studies on the gas-phase elimination kinetics of 2-arylethyl N,N-dimethylcarbamates [(CH3)2NCOOCH2CH2Z, ZÂ =Â 4-CH3C6H4, 4-CH3OC6H4, 4-NO2C6H4]

The gas-phase elimination kinetics of 2-arylethyl N,N-dimethylcarbamates, (CH3)2NCOOCH2CH2Ar, has been studied at the ab initio MP2/6-31G and MPW1PW91/6-31G(d,p) levels of theory. These carbamates produce N,N-dimethylcarbamic acid and the corresponding 4-substituted styrene in a rate determining step. The unstable intermediate N,N-dimethylcarbamic acid rapidly decarboxylate through a four-membered cyclic transition state to give dimethylamine . These calculations imply a concerted, non-synchronous six-membered cyclic transition state type of mechanism. The present results support the fact that the acidity of the benzylic hydrogen as an important factor for faster elimination rates.