F. A. LONGAND R. J. KOKES
2232
proach a limiting association number somewhere between three and four. This again is indicative of the similarity of these two liquids. On the other hand, triethylsilanol is definitely less associated than either trimethylsilanol or t-butyl alcohol, while 3-ethylpentanol-3 exhibits essentially no association. This result is not entirely unexpected since one would anticipate that the more highly hindered ethyl derivatives should be less associated than their methyl analogs. Dipole Moments.-The dipole moments of triniethylsilanol, triethylsilanol, and 3-ethylpentanol3 were evaluated from the dielectric properties of the pure liquids.22 The experimental data are summarized in Table V in which 1' is the molar
volume of the liquid a t 20°, tan 6 is the loss factor, E is the dielectric constant a t 20' and 1000 cycles and p is the dipole moment in Debye units. The dipole moment t-butyl alcohol has been reported to be 1.74 D (Onsager moment).2Y The dipole moments vary considerably from the values which would be predicted for the unassociated liquids. This result is to be expected on the basis of the data obtained in careful studies of the dielectric properties of a1cohols.24,33Such behavior may be attributed to strong forces of association in the liquid state, as indicated by the high values of the entropies of vaporization and the high degree of association in cyclohexane solution. Acknowledgment.-The authors express their appreciation to Dr. S. W. Kantor and Dr. J. D. Hoffman for their many helpful suggestions.
TABLE 1 DIELECTRIC PROPERTIES V lCHa)ib~oH 111 z IOII~CH~)3biOII 152 'I (CIIaCH2)aCOH I?X 0
tall 6
10oooz 000I 002
f
P
7 17 o 0: 2 b6 r 02 3 2 1 i 02
I o i io IO 0 0 2 + 08 I 13 f 03
Vol. 7 5
(23) S. I1).
SCHESECTADY, S . Y.
( 2 2 ) L.Onsager, Trrrs J
