Correlation of Nuclear Quadrupole Interaction Frequencies with Polarographic Half-Wave Potentials

Abstract

WHEN the nuclear quadrupole interaction frequencies of some aryl iodo-compounds are plotted against the corresponding half-wave potentials of these compounds at pH 7 (Fig. 1) a general linear trend is obvious; but the departure from linearity in the case of the iodoanilines is more serious (points not shown on graph). The data are taken from results obtained by E. Gergely and me¹, those of Colichman and Liu², and the quadrupole interaction measurements of Hatton and Rollin³, and of Barnes, Miller and Wooten⁴. Colichman and Liu have attempted a correlation of their polarographic data on iodo-compounds with Hammett's σ-function. Hatton and Rollin have attempted a similar correlation of their quadrupole data and Hammett's σ for bromine and iodine compounds. However, Colichman and Liu found the same misbehaviour of p-iodoaniline as we did, and it is equally obvious that the m- and p-di-iodobenzenes (as evidenced from our own results which are not substantially different from theirs) would not fit their straight line. On the other hand, Hatton and Rollin found, in their quadrupole – σ relationship, that these three substances fell very well into line. It is clear that the triangular agreement we expect to find from the results of these four groups of workers is very imperfect, and the interrelation of the three phenomena greatly in need of clarification.