Solvatochromic comparison method

Kamlet MJ, Abboud J-L, Taft R (1977) The solvatochromic comparison method. 6. The it scale of solvent polarities. JACS 99 6027-6038... 

Application of the solvatochromic comparison method (Kamlet and coworkers80) reveals a competition between intermolecular and intramolecular hydrogen bonding in molecules bearing both donor and acceptor groups81 such as 17. 

In 1976, Kamlet and Taft introduced their solvatochromic comparison method [25, 26], The hydrogen-bond donor acidity a and basicity /3 together with the solvent polarity and polarizability jv were employed to correlate the solvent effects on reaction rates, equilibria, and spectroscopic properties XYZ according to equations of the form... 

Kamlet MJ, Taft RW (1976) The solvatochromic comparison method. 1. The /6-scale of solvent hydrogen-bond acceptor (HBA) basicities. J Am Chem Soc 98 377-383. 

Sadek, P.C., Carr, P.W., Doherty, R.M., Kamlet, M.J., Taft, R.W., and Abraham, M.H. Study of retention processes inreversed-phase high-performance liquid chromatography by the use of the solvatochromic comparison method. Anal. Chem., 57(14) 2971-2978, 1985. 

Taft, R. W. and M. J. Kamlet. 1976. The solvatochromic comparison method. 2 - bale of solvent hydrogen-bond donor (HBD) aciditiesJ. Am. Chem. So 8 2886-2894. 

Fig. 7-3. Illustration of the solvatochromic comparison method according to [237]. Reference line equation v( ) = a - v j) + by. Reference solvent cyclohexane, o non-HBA and non-HBD solvents an HBA solvent.

Another remarkable IR spectroscopic parameter of solvent Eewis basicity has been introduced by Laurence et al. [239], using the so-called infrared comparison method analogous to Kamlet and Taft s solvatochromic comparison method [224]. The band maxima wavenumbers of the C=0 stretching vibration of the two homomorphs CCI3CO2H and CCI3CO2CH3 have been measured in the gas phase as well as in non-HBD and non-HBA solvents in order to establish a reference line that conforms to Eq. (7-37) cf Fig. 7-3. 

The SA scale was established using the solvatochromic comparison method of Kamlet and Taft [224, 226]. A good linear correlation (r = 0.961) has been found between the wavenumbers of the absorption maxima of dyes (52) and (53), measured in fifty non-acidic or non-HBD solvents, according to Eq. (7-40c) ... 

PC.Sadek,P.W.Carr,R.M.Doherty,M.J.Kamlet,R.W.Taft,and M.H.Abraham, Study of retention process in reversed-phase high-performance liqnid chroma-torgraphy by use of the solvatochromic comparison method, A a/. Chem. 57 (1985), 2971-2978. 

Solubility equilibrium, 24 Solubility parameter, 415 Solvation, 401 change in, 354 preferential, 403 selective, 403 Solvation and polarity, 399 Solvation energy, 403, 420 Solvation of anions, 360 Solvation shell, 403 Solvatochromic comparison method, 439... 

A rational strategy in identifying structural parameters appropriate for QSRR analysis should start from the accepted theories of chromatographic separations. These structural parameters obtained. should quantify the abilities of analytes to take part in the postulated intermolecular interactions which determine chromatographic. separations. Empirical or semi-empirical structural parameters of analytes based on the solvatochromic comparison method and on the linear solvation energy relationships (LSER) belong to that categoiy of structural descriptors. 19,40). 

The p scale was proposed to measure solvent hydrogen bond basicity, i.e. the ability of a bulk solvent to act as hydrogen bond acceptor. This scale was derived by systematic application of the solvatochromic comparison method the final p values were calculated by averaging 13 p parameters for each solvent obtained with different solutes and different physicochemical properties [Kamlet et al, 1981a Kamlet et al, 1983]. 

Taft, R.W. and Kamlet, MJ. (1976). TTie Solvatochromic Comparison Method. 2. The a-Scale of Solvent Hydrogen-Bond Donor (HBD) Acidities. J.Am.Chem.Soc., 98, 2886-2894. 

The use of 8 as a probe in the solvatochromic comparison method (paired with 7 or 5 for non-HBA solvents) was re-examined by Laurence, Nicolet and Helbert18. They used a much wider variety of EPD/HBA bases (68 in all) than those used in the construction of the ftT scale3,17 (25 solvents) (equation 8). The coefficients for the expression... 

For technical reasons, phenols are convenient reference hydrogen-bond donors for hydrogen-bonding studies. We present below their use for constructing thermodynamic and spectroscopic scales of hydrogen-bond basicity. These scales are either solute scales when the phenol and the base are dissolved in an inert solvent, or solvent scales when the phenol is studied in the pure base. In the latter case, methods such as the solvatochromic comparison method or the calorimetric pure base method have been developed to unravel the hydrogen-bond contribution to the overall solvent effect. 

Single electron transfer (SET), as antioxidant mechanism 844, 896, 897 Size exclusion chromatography 953 Slash pine bark, phenolic compounds in 944 Smiles rearrangement 466-470, 759 S Ar reactions 673 Soil samples, phenolic compounds in, analysis of 932, 965, 972, 985 field screening of 938 Sol-gel technique 1082 Solid acid catalysis 612-621 Solid-phase extraction (SPE) 930-933, 936, 942, 944-950, 955, 958, 960, 962-964, 969, 972, 985, 986, 995, 1354 Solvation energy 500, 992 Solvation free energy 5 Solvatochromic comparison method, for solvent hydrogen-bond basicity 591 Solvent effects,... 

The initial construction of this scale involved the systematic application of the solvatochromic comparison method (72). Documentation of solvent-solute hydrogen bonding interactions by this method requires that three important... 

Although the equations have been extended to cover many nonspectroscopic properties, we find it convenient to continue to refer to the method as the solvatochromic comparison method, the equations as the solvatochromic equations, the r, a, and 6 terms as the solvatochromic parameters, and the s. a. b. and d terms as the solvatochromic coefficients (cf Eq. 96). 

The 13 scale has been amended and expanded through three subsequent studies. In the first of these (76), the solvatochromic comparison method was applied to three HBD indicators, 2-nitroaniline (6), 2-nitro-p-toluidine (7), and 2-nitro-p-anisidine (8), and their corresponding N,N-dimethyl derivatives (6a, 7a, 8a). 

Although the basic principles remained the same, the next study (133) used a somewhat modified version of the solvatochromic comparison method. This was because the development of the polarity scale allowed the use of ir values as reference measures of solvent polarity, rather than I max for a related nonhydrogen-bonding indicator as in the previous examples. Thus, since where HBD solvents are excluded, total solvatochromic equations for p - tt and ir ir electronic spectral transitions take the form,... 

---