4125X-ray Crystal Structure Analysis of 14. Suitable crystals of 14 formed from ethyl acetate-hexane mixtures with space group symmetry of P1 and cell constants of a = 9.699 (2) A, b = 12.688 (4) A, c = 8.122 (3) A, cy = 96.41 (3)O, /3 = 110.88 (2)O, and y = 77.74 (2)' for Z = 2 and a calculated density of 1.353 g/cm3. Of the 2503 reflections measured with an automatic four-circle diffractometer equipped with Cu radiation, 2138 were observed ( I 1 3u4. The function Cw(lFoI -lFc1)2 was minimized to give an unweighted residual of 0.057. Tables IV, V, and VI containing the final fractional coordinates, temperature parameters, bond distances, and bond angles are available as supplementary material.Acknowledgment. We thank Drs. S. Danishefsky, G. Hartman, and D. Claremon for helpful discussions held during the course of this work. We are indebted to John Moreau for microanalytical combusion analysis, J. Murphy for selected NMR spectra, and M. Banker for typing the manuscript. Dr. S. Pitzenberger carried out the NMR studies on 9 and 13.Registry No. -[ 1,3-dithian-2-yl]-5-nitrobenzyl alcohol, 98015-14-6; 2-[ 1,3-dithian-2-yl]-5-nitrobenzaldehyde, 98015-15-7.'3c chemical shifts of /3-carbon atoms in 17 series of substituted styrenes have been used to establish u13 substituent constants for nine para and seven meta substituents. The u13 values are similar to u+ values for electron-donating substituents, but are somewhat elevated for the cyano and nitro groups in both meta and para positions. Despite this, the use of mixed constants, u' for electron donors and u-for electron withdrawers, does not enhance the correlations. In dual substituent parameter (DSP) treatments, Swain's field and resonance parameters, F and R, give very slightly better correlations than do Taft's parameters, U I and any one of the four standard uR scales. The Swain and Taft approaches agree closely on the relative amounts of electron supply and demand through resonance and field effects. The u13 scale based on @-carbon shifts fails completely to correlate the shifts of the a-carbon atoms. In this case, Swain's parameters are clearly superior to any combination of the Taft sets. These results suggest that, at least for the 289 compounds comprising the data set reported here, the use of multiple resonance scales in DSP treatments is perhaps unjustified.
