
%0 Journal Article
%A Kelly, DP 
%A Spear, RJ 
%T Carbon-13 N.M.R. studies of carbocations. II. An investigation of the correlation between carbon chemical shifts and &#963;<sup>+</sup> constants for 1-phenylethyl cations
%J Australian Journal of Chemistry
%D 1978/06/01
%V 31
%N 6
%P 1209-1221
%K 
%R https://doi.org/10.1071/CH9781209
%U https://www.publish.csiro.au/paper/CH9781209 
%X Eighteen 1-methyl-1-phenylethyl (cumyl) (1) and 1-phenylethyl (styryl) (2) carbocations have been prepared in known concentration in FSO3H/SbF5 solution from their corresponding carbinols and their 1H and 13C spectra have been measured. The correlations of both the methyl 1H shifts [&#948;H(Me)] and methyl 13C shifts [&#948;C(Me)] with the cationic carbon shifts [&#948;(C+)] have been determined. In the case of &#948;C(Me) curves are obtained indicating non-linearity of chemical shifts with charge density. Correlations of &#948;(C+) with Brown's &#963;+ constants are only fair, the deviation from linearity being interpreted in terms of non-linear dependence of either &#948;(C+) or &#963;+, or both, on charge density at this level of charge. The use of an enhanced substituent constant (&#963;++) and/or the dual substituent parameter equation improves the correlation. Non-linearity in the plot of &#948;(C 1) against &#963;+ reported for 2-arylnorborn-5-en-2-yl(4) and 2-arylnorbornan-2-yl cations (5) has been shown to occur also in the case of &#948;C(Me) of the cumyl cations (1). The implications of this finding with respect to the structures of (4) and (5) are discussed. 
