PCM solvation model

Bulk effects of the aqueous solvent have been evaluated by C-PCM solvation model. The specific effect of the solvation on the alkylation pathways has also been... 

Despite the importance of the oxidative polymerization of 5,6-dihydroxyin-dole, in the biosynthesis of pigments, little experimental data are known on the oxidation chemistry of the oligomers of 1. For such reasons, three major dimers of 1, such as 2-4 (Scheme 2.9), have been computationally investigated at PBEO/ 6-31+G(d,p) level of theory both in gas and in aqueous solution (by PCM solvation model) to clarify the quinone methide/o-quinone tautomeric distribution. 

SCHEME 2.10 Structures and relative energies (kcal/mol) of several tautomers/conformers resulting from the bielectronic oxidation of 2-4, computed at the PBE0/6-31 + G(d,p) level in vacuum and in aqueous solution (in parenthesis, by PCM solvation model, data from Ref. [19]). 

The base catalysis and the monoelectronic reductive activation processes have been described by a computational investigation at the R(U)B3LYP/6-31 + G(d,p) level of theory for the model imide NI (Scheme 2.14) 47 both in the gas phase and in aqueous solution, using PCM solvation model.40... 

Table 7. Free activation energies (BSl, PCM solvatation model) for the transition states (in kcal/mol) of the reaction of substrates 1-9 with permanganate. ...

The values shown in [ ] calculated at B3LYP/6-311 + G //B3LYP/6-31G level using the PCM solvation model and corrected to 298 K. 

DFT was employed to study the mechanism of ammonolysis of phenyl formate in the gas phase, and the effect of various solvents on the title reaction was assessed by the polarizable continuum model (PCM). The calculated results show that the neutral concerted pathway is the most favourable one in the gas phase and in solution.24 The structure and stability of putative zwitterionic complexes in the ammonolysis of phenyl acetate were examined using DFT and ab initio methods by applying the explicit, up to 7H20, and implicit PCM solvation models. The stability of the zwitterionic tetrahedral intermediate required an explicit solvation by at least five water molecules with stabilization energy of approximately 35 kcalmol-1 25... 

The transition structures for the hydrolysis reactions of methyl, /-butyl, and ada-mantyl chlorides in the gas phase and in water were calculated using the B3LYP/6-31-G(d) level of theory and the PCM solvation model.82 In the gas phase, backside attack is strongly favoured for the methyl chloride reaction and slightly favoured for the t -butyl chloride reaction. Frontside attack is favoured for the adamantyl chloride... 

Mikkelsen). Linear and nonlinear response functions have been implemented at the MCSCF level by Mikkelsen et al. [13], for a spherical cavity, and by Cammi et al. [14] and by Frediani et al. [15] for the PCM solvation models. 

M. Cossi, N. Rega, G. Scalmani and V. Barone, Energies, structures, and electronic properties of molecules in solution with the C-PCM solvation model, J. Comput. Chem., 24 (2003) 669. 

VBPCM Valence bond polarized continuum model. A VB computational method that incorporates solvent effect by using the PCM solvation model. The method can be coupled with VBSCF, BOVB, and VBCI. 

Table 5 Free activation energies (BS1, PCM solvation model) for all transition states...

Molecular geometries were optimized using Gaussian03 at a DPT B3LYP/6-31G (2d,2p) level of theory using SCI-PCM solvation model (water). Effective core... 

A theoretical study based on MP2/6-31+G(d,p) and HF/6-31G(d) ab initio quantum mechanical calculations coupled with Langevin dipoles (LD) and polarised continuum (PCM) solvation models have been carried out by Florian and Warshel [387] to achieve a first systematic study of the free energy surfaces for the hydrolysis of methylphosphate in aqueous solution. The important biological implication of this work is the fact that since the energetics of both the associative and the dissociative mechanics are not too different, the active sites of enzymes can select either mechanism depending on the particular electrostatic environment. This conclusion basically means that both mechanisms should be considered, and this fact seems to contradict some previous studies which have focused on phosphoryl transfer reactions. 

Although there is a very fast (on the NMR time scale) double proton transfer in quinoline 123, the enaminone/enolimine tautomers 123a and 123b are the only ones present in the chloroform solution. Ab initio calculations of the relative stabilities of tautomers using the PCM solvation model produced results contradictory to the experimental data (03CEJ2710). 

Figure 11.6 Harmonic vibrational spectra for (adenine)(H2 0)52 computed at the MM/PCM level, using two different smooth implementations of the C-PCM solvation model. Harmonic frequencies were computed via finite difference of analytic energy gradients and convolved with 10 cm Gaussians. Arrows indicate FIXPVA peaks with no obvious SWIG analogues, and the inset blows up the region of the spectrum < 4000 cm . Reprinted from Ref [41] cop5oight 2010 American Chemical Society.

Scheme 7.13 Decomposition of the ruthenium catalyst via the activation of the ortho C-H bond on the A/-phenyl group. Gibbs free energies in kcal mol with respect to the 14-electron ruthenium benzylidene complex are given in parentheses. Calculations were performed at the BP86/SDD-SVP level of theory with lEF-PCM solvation model (CHjClj solvent). Adapted from Ref [59].

Fig. 13 Photo-absorption spectra of 4-acac-coumarin anion in methanol solution calculated at the TD-DFT (B3LYP/6-31G ) level, using a PCM solvation model (a), and measured experimentally in M methanol solutions (b). The computed absorption bands have been convoluted with a Gaussian function with FWHM = 90 nm to model the solution inhomogeneous broadening. Figure reproduced from Ref.53, Copyright 2011, American Chemical Society.

---