Solution solvent effects

Caution For ionic reactions in solution, solvent effects can play a significant role. These, of course, are neglected in calculations on a single molecule. You can obtain an indication of solvent effects from semi-empirical calculations by carefully adding water molecules to the solute molecule. 

For condensed species, additional broadening mechanisms from local field inhomogeneities come into play. Short-range intermolecular interactions, including solute-solvent effects in solutions, and matrix, lattice, and phonon effects in soHds, can broaden molecular transitions significantly. 

Chuang, Y.-Y., Radhakrishnan, M. L., Fast, P. L., Cramer, C. J., and Truhlar, D. G. 1999. Direct Dynamics for Free Radical Kinetics in Solution Solvent Effect on the Rate Constant for the Reaction of Methanol with Atomic Hydrogen ,. /. Phys. Chem. A, 103, 4893. 

The analysis of the transient fluorescence spectra of polar molecules in polar solvents that was outlined in Section I.A assumes that the specific probe molecule has certain ideal properties. The probe should not be strongly polarizable. Probe/solvent interactions involving specific effects, such as hydrogen-bonding should be avoided because specific solute/solvent effects may lead to photophysically discrete probe/solvent complexes. Discrete probe/solvent interactions are inconsistent with the continuum picture inherent in the theoretical formalism. Probes should not possess low lying, upper excited states which could interact with the first-excited state during the solvation processes. In addition, the probe should not possess more than one thermally accessible isomer of the excited state. 

Specific Solute-Solute and Solute-Solvent Effects... 

Developments in experimental and computational science have shed light on phenomena in bioenvironments and condensed phases that pose significant challenges for theoretical models of solvation [27]. Tapia [22] raises the important distinction between solvation theory and solvent effects theory. Solvation theory is concerned with direct evaluation of solvation free energies this is extensively covered by recent reviews [16,17]. Solvent-effect theory concerns changes induced by the medium onto electronic structure and molecular properties of the solute. Solvent-effect theory is concerned with molecular properties of the solvated molecule relative to the properties in vacuo as such it focuses on chemical features suitable for studying systems at the microscopic level [23]. Extensive reviews of different computational methods are given in a book by Warshel [24]. 

Ahyd// was measured in acetic acid solution. Solvent effects for alkenes in this experimental method cause the measured Ahyd// to be very roughly 0.7 kcal mol 1 less exothermic than gas-phase values, which would lead to a corrected value of — 26.74(0.44) kcal mol 1 = —111.9 kJ mol 1. This entry is the mean of 12 separate thermochemical experiments made over a 10-year period. An extra digit is carried in the uncertainty when this measurement is used as an indicator of the overall uncertainty of the method. 

Ahyd7/ was measured in acetic acid solution. Solvent effects are significant for the dienes and may cause the measured enthalpy changes to be as much as 1.5 kcal mol 1 less exothermic than the gas-phase values. 

Ahyd// was measured in acetic acid solution. Solvent effects are significant for the alkynes and may cause the measured enthalpy changes to be as much as 2.5 kcal mol"1 less exothermic than values measured in the gas phase or in an inert solvent. See also Sicher, J. Svoboda, M. Zavada, J. Turner, R. B. Goebel, P. Tetrahedron, 1966, 22, 659-671. 

AhydH was measured in acetic acid solution. Solvent effects are significant for the... 

As emphasized recently by Corma [26], condensation of benzaldehyde and ethylcyanoacetate, without solvent, is an interesting reaction to check the number and the strength of the basic sites. However, when this reaction is carried out in solution, solvent effect plays an important role on the kinetic of the reaction. For this reason, we have compared the activities of different zeolites calcinated at 5S0°C, using similar experimental conditions (Table 2)... 

Phosphorus compounds give resonances in characteristic ranges depending primarily on the oxidation state and coordination munber of the phosphorus atoms present (Table 1). Chemical shifts also depend on the pH, concentration, and salt content of the solution, solvent effects, and the electronegativity of any substituents. Since the phosphorus atom is a comparatively reactive center, it can usually... 

Solvent effects were found to be quite important in stabilizing charged complexes, especially for the outer-sphere mechanism. In general, outer-sphere reactions are found to have lower activation barriers than those for inner-sphere reactions. This is due to the enhanced charge stabilization due to the presence of solution. Solvent effects play a small role in altering the energy landscape. The influence of solvation has been included and has been estimated using the reaction field theory expressions. Solvation corrections may vary between -1 and -12 kJ/mol. 

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