Solvents dipole moments study

If fluocophoces ate sensitive to Ite reaction field in a solvem, why not use elediic fields to measure theexcited-state dipole moments Sudi studies have been attempted. However, the efiects are two orders of magnitude smaller than the effects due to solvent reaction fields, even when one is working near the dieleciric breakdown voltage. ... 

The theoretical approach based on the HNC integral equation is described in the context of ionic specificity. Two levels of description of the water medium are considered. Within the Primitive Model (continuous solvent), ionic specificity is introduced via effective, solvent-averaged, dispersion forces. The agreement with experimental data in bulk or at air-water interfaces is only partial and illustrates the limits of that approach. Within the Born-Oppenheimer model, the molecular HNC equation is solved with an explicit description of the solvent molecules (SPC water). Ionic and solvent profiles in bulk and at interfaces are enriched by short-range osdUated structures. The ionic polaris-ability is introduced via the self-consistent mean-field theory, the polarisable ions carrying an effective, fixed dipole moment. The study of the air-water interface reveals the limits of the conventional HNC approach and the needs for improved integral equations. 

In 1961 Berson et al. were the first to study systematically the effect of the solvent on the endo-exo selectivity of the Diels-Alder reaction . They interpreted the solvent dependence of the endo-exo ratio by consideririg the different polarities of the individual activated complexes involved. The endo activated complex is of higher polarity than the exo activated complex, because in the former the dipole moments of diene and dienophile are aligned, whereas in the latter they are pointing in... 

In a combined experimental/computational study, the vibrational spectra of the N9H and N7H tautomers of the parent purine have been investigated [99SA(A) 2329]. Solvent effects were estimated by SCRF calculations. Vertical transitions, transition dipole moments, and permanent dipole moments of several low-lying valence states of 2-aminopurine 146 were computed using the CIS and CASSCF methods [98JPC(A)526, 00JPC(A)1930]. While the first excited state of adenine is characterized by an n n transition, it is the transition for 146. The... 

The racemization of the phosphine (118) has been followed by optical rotation. The lack of a solvent effect indicates that there is little change in dipole moment in the formation of the planar transition state. Circular dichroism has been used to study the interactions of nucleotides with proteins and DNA with a histone. Faraday effects have been reviewed. Refraction studies on chloro-amino-phosphines, fluoro-amino-phosphines, and some chalcogenides are reported. 

MD simulations in expHcit solvents are stiU beyond the scope of the current computational power for screening of a large number of molecules. However, mining powerful quantum chemical parameters to predict log P via this approach remains a challenging task. QikProp [42] is based on a study [3] which used Monte Carlo simulations to calculate 11 parameters, including solute-solvent energies, solute dipole moment, number of solute-solvent interactions at different cutoff values, number of H-bond donors and acceptors (HBDN and HBAQ and some of their variations. These parameters made it possible to estimate a number of free energies of solvation of chemicals in hexadecane, octanol, water as well as octanol-water distribution coefficients. The equation calculated for the octanol-water coefficient is ... 

Freitag and John [96] studied rapid separation of stabilisers from plastics. Fairly quantitative extraction (>90% of the expected content) of stabilisers from a powdered polymer was achieved by MAE within 3 to 6 min, as compared to 16 h of Soxhlet extraction for the same recovery. MAE and Soxhlet extraction have also been compared in the analysis of cyclic trimer in PET [113]. On the other hand, Ganzler et al. [128] compared the extraction yields for various types of compounds from nonpolymeric matrices for microwave irradiation with those obtained by the traditional Soxhlet or shake-flask extraction methods. Microwave extraction was more effective than the conventional methods, in particular in the case of polar compounds. As expected, the efficiency of the former is high especially when the extraction solvents contain water. With the high dipole moment of water, microwave heating is more... 

Tunon et al.194 studied the water molecule in liquid water. The sample of conformations by the microscopic environment (water in this case) was obtained using Monte Carlo technique. The energy was calculated as in the approach of Stanton et al.189 i.e., using Eqs. 4.25 and 4.26. The solvent induced increase of the dipole moment amounted to 0.61 Debye in line with the results by Wei and Salahub and close to the experimental value of 0.75 Debye. The solvation enthalpy amounted —12.6 kcal/mol, while the value calculated by Salahub and Wei and the experimental ones were —10.4 kcal/mol and —9.9 kcal/mol, respectively. 

Microwave heating is achieved with a pulse of microwave energy generated within a magnetron. The only requirement for the use of this heating method is that the solvent has a permanent dipole moment.24 This technique can be employed to study reactions in non-aqueous solvents since the presence of electrolytes is not necessary.30 However, the temperature changes attained were much lower than in the case of Joule or laser heating.24... 

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