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High‐Pressure Reaction Profiles and Activation Volumes of 1,3‐Cyclohexadiene Dimerizations Computed by the Extreme Pressure‐Polarizable Continuum Model (XP‐PCM)
Author(s) -
Chen Bo,
Houk K. N.,
Cammi Roberto
Publication year - 2022
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202200246
Subject(s) - polarizable continuum model , activation energy , chemistry , activation barrier , thermodynamics , polarizability , thermal , reaction mechanism , computational chemistry , chemical physics , density functional theory , catalysis , molecule , organic chemistry , physics , solvation
Quantum chemical calculations are reported for the thermal dimerizations of 1,3‐cyclohexadiene at 1 atm and high pressures up to the GPa range. Computed activation enthalpies of plausible dimerization pathways at 1 atm agree well with the experiment activation energies and the values from previous calculations. High‐pressure reaction profiles, computed by the recently developed extreme pressure‐polarizable continuum model (XP‐PCM), show that the reduction of reaction barrier is more profound in concerted reactions than in stepwise reactions, which is rationalized on the basis of the volume profiles of different mechanisms. A clear shift of the transition state towards the reactant under pressure is revealed for the [6+4]‐ene reaction by the calculations. The computed activation volumes by XP‐PCM agree excellently with the experimental values, confirming the existence of competing mechanisms in the thermal dimerization of 1,3‐cyclohexadiene.