Molecular Dynamics Simulations of the Initial-State Predict Product Distributions of Dediazoniation of Aryldiazonium in Binary Solvents

The
dediazoniation of aryldiazonium salts in mixed solvents proceeds
by a borderline SN1 and SN2 pathway, and product
distribution should be proportional to the composition of the solvation
shell of the carbon attached to the −N2 group (ipso
carbon). The rates of dediazoniation of 2,4,6-trimethylbenzenediazonium
in water, methanol, ethanol, propanol, and acetonitrile were similar,
but measured product distributions were noticeably dependent on the
nature of the water/cosolvent mixture. Here we demonstrated that solvent
distribution in the first solvation shell of the ipso carbon, calculated
from classical molecular dynamics simulations, is equal to the measured
product distribution. Furthermore, we showed that regardless of the
charge distribution of the initial state, i.e., whether the positive
charge is smeared over the molecule or localized on phenyl moiety,
the solvent distribution around the reaction center is nearly the
same.