1752
isomers and their vibrational frequencies is 73.8, assuming free rotation. Gray and Reevcs'4 have found a barrier 10,500 f 2000 cal. ascribed to hindered rotation of the S O group. When an entropy deficit of 3.0 e.u. corresponding to this barrier is subtracted, there still remains an entropy deficit of 4 f 0.7 e.u. between the calculated and experimental value. Gray and Pratt2 calculated the maximum entropy due to free rotation of the methyl group to be 3.58 e.u. and that for the N O group to be 5.80. The entropy deficit 4 i 0.7 e.u. found in the present work thus corresponds to an essentially fixed methyl group. Such a high barrier to rotation of the methyl group is reasonable since in methyl nitrate the distance closest approach of a methyl group H to 0 is 1.8 A., whereas the structyral data given by R o g o ~ s k i lindicate ~ only 1.3 A. for this distance in methyl nitrite. Further evidence for a large barrier to methyl group rotation in methyl nitrite is given by Tarte's16 analysis of the C-D vibrational bands in CHzDONO and Wagner's17 interpretation of the intensity variation of the Raman -OS0 lines which was ascribed to hydrogen bonding. Acknowledgments.-This research was supported in part by a grant from the Research Corporation, and by a grant from the National Science Foundation. (14) (15) (16) (17)
Vol. 66
NOTES
P. Gray and L. W. Reeves, J . Chem. Phys., 32, 1878 (1960). F. Rogowski. Ber., B76, 244 (1942). P. Tarte, Bull. soc. chim. Belges, 62, 401 (1953). J. Wagner, J . phys. radium, 18, 526 (1954).
HAMMETT CORRELATIOKS FOR THE SOLUBILITY OF GASEOUS H7i7DROGEK CHLORIDE IK CERTAIN AROMATIC
SYSTEMS BY MORRISRAPOPORT, C. KINNEYHAS COCK,^ AND EDWARD A. MEYERS Department of Chemasfry. The A . and M. College of Texas, CoZZege Statton, Texas Received February 9, io62
I n the typical Hammett relation, a functional group property, such as an equilibrium or rate constant, is involved. In sharp contrast, there now are numerous quantitative relationships in the literature between a molecular property, such as the energy of electronic spectral excitations ( h ~ )and , Nammett's U-values. W e have therefore looked for Hammett relations in the realm of solubility phenomena, which are also characterized by the lack of a localized "reaction" site and where gross molecular structure similarly plays an important role. We have found that the data collected by Brown and Brady3 for the solubility of hydrogen chloride in solutions of some aromatic compounds follow a linear Hammett relation. Because of recent successful spectra-structure (1) Abstracted from a portion of the Ph D. DisRertation of 111 R , Mag, 1961. (2) To whom inquiries should be addressed, a t Department of Chemistry, The A. and &I. College of Texas, College Station, Texas. (3) H. 6. Brown pnd J. 33. R r s d y , J. Am. Chsm, S a o . , 74, 33713 (10$21
