The Mode of Transmission of Electrical Effects: Evidence from NMR Spectra
Pratt Institute (PI), 200 Willoughby Avenue, New York, NY 11205, United States
We have studied the transmission of electrical effects [1-4] as a function of substituent chemical shifts, scs, in 1H, 13C, and 19F NMR spectra of XGY in which X is the substituent, Y is the atom responsible for the chemical shift and G is the skeletal group to which X and Y are bonded. The C atom of G which is bonded to X is sp2 hybridized. We have shown that L values obtained from correlation with the LDR equation are a measure of the magnitude of electrical effect transmission. Preliminary results for correlation of -L values of XG-19F scs with the equation
log (-L) = a1 log n + a0 (1)
gives the regression equation (2) on exclusion of the value for G of 6,2-naphthalene.
log (-L) = -3.20 (± 0.580) log n + 2.99 (± 0.401) (2)
r2, 83.59; F, 30.56; Sest. 0.206; S0, 0.468; Ndp, 8 .
This corresponds to a modified field effect with a dependence on 1/r3.
We have also examined the composition of the group electronegativity parameters often used in the description of 19F scs. They are a function of electrical effect and polarizability parameters . The regression equation is:
σχ = 0.424(± 0.107) σe - 0.329 (± 0.0929)σd -1.10(± 0.468) (3)
R2, 84.23; A100R2, 81.36; F, 17.80; Sest, 0.0897; S0, 0.470; Ndp, 14.
It seems likely that there is at least one additional variable as yet undiscovered.
 M. Charton, J. Phys. Org. Chem. 1999, 12, 275-282: The Nature of Electrical Effect Transmission.
 M. Charton, B. I. Charton, J. Chem. Soc. Perkin Trans. 2, 1999, 2203-2211: The Mode of Transmission of Electrical Effects.
 M. Charton, Coll. Czechoslov. Chem. Commun. 1999, 64, 1849-1876: The Nature and Transmission of Substituent Electrical Effects in Alicyclic Solvolysis.
 M. Charton, B. I. Charton, J. Phys. Org. Chem. 2001, 14, 832-838: The Mode of Transmission of Electrical Effects. Evidence from Infrared Stretching. Frequencies.
 W. Adcock, J. E. Peralta, H. Ruben. Magn. Res. Chem. 2003, 41, 503-508: Computation and Analysis of 19F Substituent Chemical Shifts of Some Bridgehead-Substituted Polycyclic Alkyl Fluorides.
Presentation: oral at 18th Conference on Physical Organic Chemistry, Symposium 1, by Marvin Charton
See On-line Journal of 18th Conference on Physical Organic Chemistry
Submitted: 2006-05-23 12:18 Revised: 2009-06-07 00:44
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