Solvent configuration calculations, theoretical

The authors explain that there is a slight equilibrium between attractive (electrostatic and dispersive) and repulsive (steric) forces in the fundamental and excited state of the adducts, depending on solvent configuration and the chromophore structure. The homochiral complexes have been found to be more stable than their heterochiral counterparts. Another R2PI study by Speranza [113] used R-(+)-l-phenyl-1-propanol as model, to study the interaction with several solvents as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, S-(+)-2-butanol, R-(—)-2-butanol, 1-pentanol, S-(+)-2-pentanol, R-(—)-2-pentanol, and 3-pentanol. The experimental results had the support of theoretical calculations at the B3LYP/6-31G level. In all cases studied, the homochiral complexes were found to be more stable than the heterochiral ones, both in fundamental and excited states, as well as for the corresponding ionic adducts. 

Note the two terms, y.(X + SO V) and oc(0 + solv), are calculated for the same MC configurations and same theoretical models, but with and without the solute, respectively. Therefore, in the configuration without the solute, there is a vacancy in the center of the configuration, and the difference of these two terms gives the polarizability of the solute under the environment of the solvent. The separation is expected to work well for the cases where the interaction polarizability is small. This is expected to be the case of liquid argon. 

Numerous theoretical studies on DMABN have been carried out, and many of them confirm the greater validity of the TICT model. The main body of such calculations, however, has been limited to the isolated system, while few examples including solvent effects can be quoted. " On the contrary, the phenomenon is strongly related to solvation and thus explicit considerations of solvent interactions are very important to get a more accurate understamding of the experimental evidence on the specific effects due to the presence of polar solvents. Here we summarize the results of the correlated study of DMABN both in vacuo and in solution we have published on the Journal of American Chemical Society. In this study we have used the multireference perturbation configuration interaction (Cl) method, known with the CIPSI acronym, which has been coupled to the PCM-IEF solvation continuum model. ... 

In Equations (9-148), (9-149), and (9-154), appears everywhere as a constant. Theoretical and experimental investigations have shown that does not depend on either the constitution or the configuration of the polymer or on the chemical nature of the solvent used. As a proportionality factor between the radius of gyration and the hydrodynamic volume, 4> is only related to the expansion of the coil in the relevant solvent, i.e., to the value of a or 6. The theoretical calculation leads to... 

For example, Mikolajczyk and Kielbasinski [172-175] studied the acylation of phosphine boranes 259 using CAL (Chirazyme ) lipase from Candida Antarctica and Lipase AK from Pseudomonas fluorescencs (Scheme 84). The best enantios-electivity was attained in the lipase AK-catalyzed acylation of 259 in cyclohexane solution with vinyl butyrate as an acyl donor (99% ee) for unreacted hydroxypho-sphinate 259 and 43% ee for the acylated product 260. The E-values were on the level of 15. The enzymatic resolution of alkoxy (hydroxymethyl)phenyl-phosphine boranes (/ /S)-261 was achieved by trans-esterification with vinyl acetate in the presence of CALB, Amano AK, Amano PS, Amano AH, and LPL in various solvents. The best enantioselectivity of imreacted alcohol 261 and acylated product 262 was attained in cyclohexane (37% ee, conversion 50%). Kielbasinski [176] recently reported some additional data, including theoretical calculations and more accurate chemical correlation, which proved that the borane reduction of acyclic phosphine oxides proceeded with inversion of configuration at the phosphoms center. On this basis, the stereochemistry of the enzymatic reaction was ultimately determined (Scheme 85). 

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