The effects of solvation in the SN2 reaction Cl-(H2O)+CH3Cl were investigated using our own Nlayered integrated molecular orbital and molecular mechanics (ONIOM) polarizable continuum model (PCM) method [Vreven T, Mennucci B, da Silva CO, Morokuma K, Tomasi J (2001) J Chem Phys 115:62–72], which surrounds the microsolvated ONIOM system with a polarizable continuum. The micro solvating water molecule tends to stay in the vicinity of the original chloride ion. In the ONIOM calculations, Cl-+CH3Cl was considered as the ‘‘model’’ system and was handled with the ‘‘high-level’’ method, while the explicit water molecule in the microsolvated complex was treated at the ‘‘low-level’’. The molecular orbital (MO) and ONIOM(MO:MO) calculations allow us to assess the errors introduced by the ONIOM extrapolation, as well as the effects of microsolvation on the potential-energy surfaces. We find that ONIOM[B3LYP/6-31+G(d,p):HF/6-31+G(d,p)] and ONIOM[B3LYP/6-31+G(d,p):HF/6-31+G(d,p)]-PCM methods are good approximations to the target B3LYP/6-31+G(d,p) and B3LYP/6-31+G(d,p)-PCM methods. In addition, severalapproximate (computationally less expensive) schemes in the ONIOM-PCM method have been compared to the exact scheme, and all are shown to perform well.
Theoretical study of the SN2 reaction of Cl-(H2O)+CH3Cl using the ONIOM-PCM method
MENNUCCI, BENEDETTA;
2004-01-01
Abstract
The effects of solvation in the SN2 reaction Cl-(H2O)+CH3Cl were investigated using our own Nlayered integrated molecular orbital and molecular mechanics (ONIOM) polarizable continuum model (PCM) method [Vreven T, Mennucci B, da Silva CO, Morokuma K, Tomasi J (2001) J Chem Phys 115:62–72], which surrounds the microsolvated ONIOM system with a polarizable continuum. The micro solvating water molecule tends to stay in the vicinity of the original chloride ion. In the ONIOM calculations, Cl-+CH3Cl was considered as the ‘‘model’’ system and was handled with the ‘‘high-level’’ method, while the explicit water molecule in the microsolvated complex was treated at the ‘‘low-level’’. The molecular orbital (MO) and ONIOM(MO:MO) calculations allow us to assess the errors introduced by the ONIOM extrapolation, as well as the effects of microsolvation on the potential-energy surfaces. We find that ONIOM[B3LYP/6-31+G(d,p):HF/6-31+G(d,p)] and ONIOM[B3LYP/6-31+G(d,p):HF/6-31+G(d,p)]-PCM methods are good approximations to the target B3LYP/6-31+G(d,p) and B3LYP/6-31+G(d,p)-PCM methods. In addition, severalapproximate (computationally less expensive) schemes in the ONIOM-PCM method have been compared to the exact scheme, and all are shown to perform well.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
