On the nature of modified composite electrical effect parameters

Abstract

It is shown that a correlation of some property, reactivity or biological activity with pure parameters can also be carried out with composite parameters to produce a model with comparable statistics. Modified composite electrical effect parameters can be obtained from known composite electrical effect parameters by means of an algorithm such asin which X is the modified composite electrical effect parameter (MCEEP), X the original composite electrical effect parameter, c a constant and m an exponent. MCEEPs were calculated from this equation with c equal to 2 and m ranging from À4 to 4 when X is m or p , and from À2 to 2 when it is þ p . They were used to model 10 sets of chemical reactivities that had previously been correlated with the pure parameters l , d and e , which represent the localized (field), intrinsic delocalized (resonance) and electronic demand sensitivity electrical effects, respectively. In most cases both the pure and the modified composite parameters give comparable fits to the data as measured by the values of 100R 2 , in accord with the prediction. The composition of the MCEEPs was a linear function of m. The advantage in using pure parameters is that they are readily interpretable. Correlations with composite parameters can be interpreted only if their composition has been determined. These results provide an understanding of the way in which topological parameters work.

Kinetics and Mechanism of the Aminolysis of Dimethyl Thiophosphinic Chloride with Anilines

“…It is well known that the P=O systems are generally more reactive than their P=S counterparts for several reasons, the so-called "thio effect", which is mainly the electronegativity difference between O and S and favors O over S. 3 The natural bond order (NBO) charges 4 of the reaction center P in the gas phase are 1.180 (1) (4), 1d which are consistent with the inductive effects of Ph (σI = + 0.12) 5 and Me (σI = -0.01) 5 ligands. Solely considering the positive charge of the reaction center P atom in the P=S (and P=O) system, the anilinolysis rate of 1 (and 2) should be slower than that of 3 (and 4), i.e., kH(1)/kH(3) < 1 [and kH (2)/kH(4) < 1].…”

Concurrent pathways to explain solvent and substituent effects for solvolyses of benzoyl chlorides in ethanol-trifluoroethanol mixtures

“…the original Hammett σ σ + ). There is a measurable resonance effect in some σ constants, 19,20 and there is also a large effect of electron-donating substituents on the C-Cl bond length and on the negative charge at the chlorine atom in benzoyl chlorides (1). 21 The stabilisation energies, calculated from equation (2), 21 were recently shown to correlate with σ, 8 so the resonance demand incorporated into…”

Marvin Charton - Correlation Analyst Par Excellence

“…Towards the end of the series, Parts IX and X were co-authored with Barbara Charton. In 1973 Charton summarized this work (with some extension) in an article of over 120 pages in Progress in Physical Organic Chemistry [2], thereby establishing a pattern of publication which he has followed on several occasions.…”