2708
SOTICS
Irol. 66
I
ing X=0l6 absorptions. The ultraviolet absorption intensity of a number of 018-labeled X=O compounds also appears to be measurably different from the parallel normal compounds.ld92 Since the absorption intensity of molecules, both in the infrared and in the ultraviolet region of the spectrum, is a function of their respective transition dipole moment, this (unexpected)lb change in the absorption intensity of X=O1s compounds made it interesting to measure their permanent dipole moment in comparison with that of the corresponding normal substances. Theoretically, however, 3.0 dipole moment of two isotopic modifications \ a the of the same compound should differ only very 2.0 slightly, mainly as the result of the change in the , ', , zero-point energy of the molecules. The calculated -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 dipole moment of HD is thus only3 5.67 X loF4D. log ( C Z / t ) , mm.2/hr. (as compared with zero for Hz). Fig. 1.-Estimation of ki and p . No dipole moment measurements of Ols-compounds seem to have been reported yet, although would increase. This is confirmed by the fact that some comparative values for various pairs of the intercepts of the straight lines increase with normal and deuterated m o l e d e s were reported4 rise in temperature. The values of k i and P were and the effect of Cl13 and S34on the moment was determined by the method of least squares. These estimated5 in one case. It thus was observed that are given in Table I. even for ammonia-& the increase in the electric moment is only small4 (0.03 D.), although the relaTABLE I tive difference in all three isotopic masses is PARAMETERS OF EQUATION 2 here very high and in spite of the fact that X-H Temp., O C . ki (mm.'/hr.) P (Dun.-*) bonds show the largest anharmonicities'j (which 26 f 1 1.08 0.206 are the main cause for the observed changes in the 31 i 1 1.47 .205 dipole moment of labeled compound^^^^^). 37 f 1 4.225 ,218 The electric moment of the following pairs of 45 f 1 4.68 ,223 X=O compounds therefore has been measured 54 f 1 5.77 ,234 accurately: (a) normal and 90 atom yo OL8-benzo59 & 1 10.8 .225 phenone, (b) normal and 54 atom % OWriphenylIf T i / T m a ,
