Solvatochromic equation

QSARs based on ionic compounds have thus been dramatically restricted due to the neglect of ion partitioning, which consequently meant that no technique was dedicated to such measurements and that modeling never took account of ionic species. To become fully accepted, potentiometry and electrochemistry at the ITIES need now to prove interesting in QSARs. As numerous lipophilicity data of ionizable compounds become available, one can expect that solvatochromic equations for ions will soon be developed in various solvent systems, which would greatly facilitate QSAR studies. 

Kamlet M. J., Abboud J.-L., Abraham M. H. and Taft R. W. (1983) Linear Solvation Energy Relationships. 23. A Comprehensive Collection of the Solvatochromic Parameters, 7i, a, and ft, and Some Methods for Simplifying the Generalized Solvatochromic Equation, J. Org. Chem. 48, 2877-2887. 

Kamlet MJ, Abboud JLM, Abraham MH, Taft RW (1983) Linear solvation energy relationships. 23. A comprehensive collection of the solvatochromic parameters, jr, a, and /3, and some methods for simplifying the generalized solvatochromic equation. J Org Chem 48 2877-2887. 

Use of Solvatochromic Equations Solvatochromic analysis for log P calculations appears to be one of the more useful approach built using linear free energy relationship (LEER) described by the general Equation (5.6) [58] ... 

A Comprehensive Collection of the Solvatochromic Parameters Jt, a, P and some Methods for Simplifying the Generalized Solvatochromic Equation./. Org. Chem., 1983,... 

Often referred to as the solvent cohesive energy density, the Hildebrand solubility parameter is considered to be a measure of the solvent contribution to the cavity term, and is used as a correction factor in the - solvatochromic equation. It is related to the general definition of London cohesive energy between two interacting species ... 

From the general solvatochromic equation, two special cases can be encountered. When dealing with effects of different solvents on properties of a specific solute, the general equation is explicitly on solvent parameters ... 

To determine the experimental first excited singlet-state dipole moments of the BPHTs, the authors established the Bakhshiev and Kawski-Chamma-Viallet solvatochromic equations, as described in previous works ([25] and references therein) (Table 5). For non-fluorescent compounds 7 and 8, no excited singlet-state dipole moment value could be obtained. 

The scale was proposed for solute HBD acidity of monomer amphihydrogen-bonding compounds acting as non-self-associated solutes [Taft, Abraham et al., 1985 Kamlet, Doherty et al, 1986a]. In particular, a, values were derived from logfC values for complexation with pyridine N-oxide in cyclohexane this set of values was successively extended through various back-calculations using the solvatochromic equation. 

We first applied the solvatochromic equation (SCE) to solvolysis of tert-butyl chloride (t-BuCl) to determine if the method could give a reasonable result for this much-studied reaction (7). Abraham et al. (11) had previously attempted correlation of these rates with the SCE without the cavity term, but as Bentley and Carter (12) have noted, an unsatisfactory result was achieved (7). First, TFE and hexafluoroisopropyl alcohol (HFIP) did not fit the correlation. Second, no rate dependence on solvent nucleophilicity 0 was found, despite other works indicating a weak dependence on this parameter (12, 13). Also, different correlations were observed for hydroxylic and nonhydroxylic solvents Bentley considered this finding to indicate that the dehydrohalogenation transition state (in nonhydroxylic solvents) and the solvolysis transition state (in hydroxylic solvents) were significantly different and thus concluded that the two types of reactions should not be included in the same correlation. 

Indeed, the difference of the mean diff (log PN 1,0) values signifies that the molecular radius of ions is approximately 1.2 A larger in OCT than in DCE. This result perfectly agrees with the fact that ions keep more water molecules when they transfer into OCT than in a less polar solvent like DCE, because of the larger solubility of water in OCT and of its H-bonding capacity, which is almost as large as in water [since the a term of its solvatochromic equation (see Table 1) is nearly zero]. 

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