Min-Hsien Liu

SOLVENT EFFECT ON ELECTROPHILIC AND RADICAL SUBSTITUTION OF TOLUENE MONONITRATION REACTIONS

Two kinds of nitrating reagents, a nitronium cation and a nitro radical (·NO2), were used in the gaseous phase toluene mononitration reaction. The closed shell calculation for electrophilic substitution and open shell calculation for radical substitution were both performed in solventless, H2O-solvated, and CH3OH-solvated molecular reaction systems. In the series of electrophilic toluene nitration reactions, both ortho-nitro toluene (o-MNT) and para-nitro toluene (p-MNT) are more abundant products than meta-nitro toluene (m-MNT), no matter what solvent is used in the reaction system. The reaction energy barrier for obtaining each kind of mononitro toluene follows a stepwise decreasing trend when the reaction is carried out in the solventless, H2O-solvated, and CH3OH-solvated systems. In all radical toluene nitration reactions, solventless or solvated, m-MNT is the most abundant product. The energy barrier data also show that the nitration reaction is more feasible in a solvated than in a solventless system. H2O has a more obvious solvent effect than CH3OH in the ·NO2 radical substitution reaction, and the H2O-solvated system provides a lower activation energy reaction path.