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The relative stabilities of the cation radicals of several Group IV substituted anilines have been determined by cyclic voltammetry. They are p -tert-butyl- > m -trimethylsilyl- > p -trimethylsilyl- > p -trimethylgermyl- ⪢ N,N -dimethylaniline radical cation. The order of stability parallels that of the compounds towards protodemetalation. CNDO/2 calculations of the charge distribution in the ground states and cation radicals of the molecules resolve the apparent, anomaly in the rates of protodesilylation of m - and p -trimethylsilyl- N,N -dimethylaniline. A mechanism for the chemical reactions of the radical cations which is consistent with the experimental and theoretical results is proposed. It involves nucleophilic displacement of the metal from the cation radical prior to the coupling of the radicals. The relative stabilities of the radical cations of the silicon compounds are in the same order as the amount of π character of the SiC bond in the radical cation. The CNDO/2 calculations indicate that this π character is due to both ( p-p )π and ( p-d )π interactions in the neutral molecules and in the radical cations.

Synopsis The Paper describes vibration methods which have been used to obtain the dynamic properties of soil in situ from measurements made at the surface. Part I of the Paper considers the propagation of surface vibrations over test lengths of about 50 ft. It is shown that the dynamic shear modulus, and the form of its variation with depth, can be ascertained from measurements of the phase velocity of the surface vibrations within the frequency range of 35 to 400 c/s. The relation between phase velocity and frequency enables the depth to be found at which there is a marked change in elastic properties such as at a transition between clay and gravel. In Part II of the Paper, a method is described for obtaining the dynamic shear modulus of the soil from the resonant frequency of a mass vibrating perpendicularly to the surface. This method enables localized measurements to be made which may be used to supplement the average data derived from the method described in Part I. Le mémoire décrit méthodes de vibration qui ont été employées pour obtenir les propriétés dynamiques élastiques d'un sol in situ par des mesures faites Ala surface. La première partie du mémoire examine la propagation des vibrations de surface sur des longueurs d'essai d'environ 15 m. On montre que l'on peut déterminer le module dynamique de cisaillement et la forme de sa variation suivant la profondeur, à l'aide de mesures de la vitesse de phase des vibrations de surface entre les limites de frèquence de 35 á 400 périodes par seconde. Le rapport entre la vitesse de phase et la frèauence permet de déterminer la profondeur à laquelle il y a un changement marqué des propriétés, comme dans le cas d'une transition entre argile et gravier. Une méthode est décrite dans la deuxième partie du mémoire pour obtenir le module dynamique de cisaillement du sol à l'aide de la fréquence résonnante d'une masse vibrant perpendiculairement à la surface. Cette méthode permet d'effectuer des mesures localisèes qui peuveni. être utilisées pour suppléer aux données moyennes dérivées de la méthode décrite dans la premiére partie.

The VUV spectra of methylvinylsilane and propylene are reported and corresponding transitions are assigned. The small red shift of the π→π* transition and the large blue shift of the σ→σ* excitation of the methyl group in methylvinylsilane may be attributed to the +I inductive effect of silicon without involving interaction between d orbitals and the π system. No evidence for a second allowed π→π transition is found in methylvinylsilane.