Thermal reaction of N-methyl-2-pyrrolidinone(NMP) and carbon disulfide(CS2) under elevated pressure leads to the formation of N-methylprrolidine-2-thione. Using density functional theory

two parallel paths of the reaction and related configurations of 4 transition states and 2 intermediates were determined. The two-step reaction mechanism was suggested and the first step was confirmed to be rate determining step. Based on the mechanism

the kinetic parameters were calculated. At 298 K

the activation energy values of path 1 and path 2 were 604.740 and 598.101 kJ8226;mol-1 respectively; at 500 K

they were 607.665 and 601.055 kJ8226;mol-1. The corresponding rate constants were 1.90×10-105

3.81×10-104

4.33×10-66 and 4.70×10-60m38226;mol-18226;s-1

respectively. According to the calculation data， it was concluded that the α-H atom near carbonyl group of NMP played an important role in the reaction via intramolecular interaction with carbonyl O atom and the reaction region was two tetratomic rings that connected with each other

and consisted of carbonyl C and O

α-C and H of NMP

in addition to C and S in CS2.