New aspects of electrophylic aromatic substitution mechanism: Computational model of nitration reaction
Simulation of polar environment of nitration reaction gave a new outlook of disputable items of its mechanism. Current data cast doubt on the existence of π-complexes and complexes with electron transfer in ordinary nitric media. Those conceptions can be suitable in gas phase or nonpolar solvents and superacid media.
Substrate reactivity (activation energy of corresponding reaction) correlates with enthalpy of σ-complex formation but not with the total heat of nitro product formation. Calculated substrate reactivity agrees with that observed in experiment.
Coulomb interaction of electrophyl and substituent can be a special factor of reactivity that influences regioselectivity of reaction.
The best index of substrate reactivity in nitration appears to be energy of protonation of the substrate.