Swain’s treatments

Swain s treatments were a reaction against the proliferation of scales of polar substituent constants. He maintained that the polar effect of any given substituent could be adequately expressed in terms of just two basic characteristics a field constant and a fixed resonance constant, cf. the four resonance parameters continue to be applied by some workers and values are included in a recent compilation of substituent constants. ... 

Analogous DSP treatments, but with differences with regard to the basis of the calculations, were proposed by Charton (1981) and by Swain s group (Swain and Lupton, 1968 Swain et al., 1983). The potential significance of polarizability effects resulted in a triple substituent parameter treatment (Taft, 1983). A slightly different... 

Table XIV lists comparative SD and /values for fittings of all the sets of Table Xlll with each of the scales of Table V, the FandR values of Swain, and with the single substituent parameter treatment, po y These statistics, coupled with structural considerations, we believe support the usefulness and uniqueness of a scale of limited generality. In general, the / values of Table XIV for the Or scale are smaller than those of the other scales by factors of from 2 to 10. The root-mean-square F values for the other scales are from 2.25 (< j (BA)) to 3 to 4 (S L,, cr (yv)) times that for. Because this analysis has demonstrated that Swain s F and R are generally inferior for the discriminating data for all four types, there appears little to encourage proliferation of these parameters.

This procedure was necessary because unique solutions were not obtained when 25 values of cx and c2 as well as 17 values of dx and d2 were derived by an iterative computer-procedure. Swain s own doubts about the results of this treatment have been emphasised by Streitwieser (1956a), who pointed out that values of do not reflect sensitivity to solvent nucleophilicity (Swain used cx/c2 to characterize reactivity). 

These began with a paper by Swain and Lupton in 1968. The approach was slightly modified and greatly extended by Hansch s group in 1973. During the first 15 years or so of its life, the Swain-Lupton treatment was applied extensively, but was also severely criticized. A revised version appeared in 1983 in a paper by Swain and coworkers ". This version was in its turn severely criticized, but also applied. The Swain-Lupton treatment was reviewed by the present author in 1978 and again more briefly in 1982. A more recent review covers also the revised version and an account of a mini-symposium in print in which several of Swain s critics set forth their views, and Swain replied . 

Table IV lists comparative SD and / values for fittings of all of the reactions of Table II and III with each of the gr scales derived in this paper. The comparison includes figures for fittings with F and R values of Swain and Lupton (S L) and fitting with the Hammett equation. We believe the results given in Table IV provide a clear confirmation of the uniqueness and limited generality of the o/2(ba) scale. Very consistently, the fit achieved by the or (BA) scale is shown in Table IV to be superior by significant factors to that achieved by any of the other scales or by the simple op treatment. This fact is clearly reflected in the overall / values and the similarly weighted root-mean-square / values, F = y/lfnif lN, sum taken over all reactions. The value of F is. 067 for the basis sets of Table II (compare with overall / of. 058). The comparable F values are. 140 for Or, . 088 for S L, and. 155 for 0(p) with the data differences as explained in Table IV. For all sets of Table IV, the corresponding figures are. 073 for o (ba). -143 for a%, . 097 for S L, and. 209 for 0(py...

Chronic HCV infection is curable, and cure is the goal of antiviral therapy. Successful treatment is characterized by a sustained virological response (SVR), defined by undetectable HCV RNA in a sensitive assay (detection limit < 50 international units (IU)/ml) 6 months after the end of therapy. Recent large-scale follow-up studies have shown no relapse or recurrence after 4-6 year s in more than 99% of patients who have an SVR (McHutchison et al. 2006 Swain et al. 2007). 

Hampshire S (1994) Nitride Ceramics. In Swain MV (ed) Structure and properties of ceramics. Cahn RW, Haasen P, Kramer EJ (eds) Materials Science and Technology, Comprehensive Treatment. VCH, Weinheim, p 119... 

Both Kamlet, Abboud, and Taft et al. s [224, 226] and Swain et aVs [265] multiparameter solvent effect treatments have an inherent weakness in so far as the solvent parameters a, and n as well as and are averaged and statistically optimized parameters the former are derived from various types of solvatochromic indicator dyes. 

Bnrak, K.W., Urbanski, S.J., Swain, M.G. Successful treatment of refractory type 1 autoimmune hepatitis with methotrexate. J. Hepatol. 1998 29 990 -993... 

S. Hampshire in Structure and Properties of Ceramics, edited by M. Swain, Volume 11 of Materials Science and Technology - A Comprehensive Treatment, Chapter 3, VCH Verlagsgesellschaft, Weinheim (1994)... 

Thompson, S., Swain, J., Kay, M., and Foster, C. F., Review Paper The treatment of pulp and paper mill effluent. Bioresource Tech., 77 275-286, 2001. 

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