Thermal decomposition and isomerization of 1-heptyl radical: a computational investigation

Abstract

A detailed theoretical study on the thermal decomposition and isomerization of 1-heptyl radical at the CBS-QB3, BH&HLYP, B3PW91, BLYP, MPW1PW91, and M06-2X levels of theory is done. The result shows that the pyrolysis mechanism of 1-heptyl radical mainly includes the isomerization, the C–C, and C–H bond scission reactions. The standard reaction enthalpies for each elementary reaction involved in this system are estimated at several density functional theory methods together with cc-pVDZ basis set and the high-level ab initio CBS-QB3 approach. The theoretical rate coefficients of conventional transition state theory with Eckart tunneling correction (TST/Eckart) for individual elementary reaction involved in the above reaction system are evaluated over the temperature range of 500–2,500 K. The calculated values are in good agreement with available experimental measurements and previous theoretical reports. Furthermore, the isomerization and decomposition reactions are selected to compare their relative importance at different temperatures. It is found that the isomerization process is more pronounced when the temperature is below 1,200 K. Product distribution of 1-heptyl radical pyrolysis is predicted based on the steady-state approximation, and the eventual products are ethylene (C2H4), propylene (C3H6), 1-butylene (C4H8), 1-pentene (C5H10), and 1-butylethylene (C6H12).