Abstract
Towards the better understanding of the important reactions included in the thermochemical conversion of coal, radical addition reactions to the substituted benzene were studied theoretically. Activation energy (E_a) and heat of reaction (ΔH_R) were estimated by using electronic structure calculations at the CBS-QB3 level combined with transition state theory. Effect of types of substituents on benzene and reactive radicals on both E_a and ΔH_R were systematically evaluated by considering a number of substituents and radicals such as hydrogen, methyl, ethyl, ethynyl, methoxyl, hydroxyl, which are typically found in thermochemistry of coal conversions. The calculations revealed that the types of addition radical exhibit a strong influence on E_a and ΔH_R, and both of which are little changed with the types of substituents. An important finding is that there are linear correlations between E_a and ΔH_R. These rules can be used to estimate E_a according to ΔH_R and eliminate the electronic structure calculations of most favorable transition state, thereby reducing the computational cost and time.
