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The reaction of a silane with ozone results in the quantitative conversion of the Si-H bond to the Si-OH moiety. The mechanism of this oxidation has been elucidated by examination of: (a) relative rate data, (b) substituent effects, (c) deuterium isotope effects, (d) low-temperature nmr, and (e) uv spectroscopy. The mechanism proposed involves fast, reversible complexation of ozone (acting as a nucleophile) with the silicon atom, rate-determining electrophilic attack of ozone on the hydridic hydrogen, and decomposition into a R3Si • • OH radical pair which recombines to produce the silanol. From the relative rate data and substituent effects, a Hammett-like value, 8 *, characteristic of substituents bound to silicon, is derived.

The Diels-Alder reaction of vinyl-, allyl-, and phenylethynylsilanes with tetraphenylcyclopentadienone was studied. In all cases, the reaction was slower than that of the carbon analogs. Allylsilanes gave the expected adducts, albeit slowly, but phenylethynylsilanes were generally unreactive, only phenylethynyltrimethylsilane affording an adduct. The reaction of vinylsilanes was complicated by the fact that the dihydrobenzene intermediate could lose either hydrogen or a silane moiety upon aromatization, resulting in a mixture of products. The product distribution was dependent upon solvent and the substituents on the silicon atom.The Diels-Alder reaction of a variety of allyl-, ethynyl-, phenylethynyl-, and vinylsilanes with tetraphenylcyclopentadienone (tetracyclone) was investigated in order to (a) evaluate the effect of placing a silicon atom a or ß to the dienophile, (b) synthesize moderately high molecular weight organosilicon compounds for evaluation as potential high temperature lubricant components,1 and (c) prepare a series of siliconcontaining monomers which could be incorporated into a Diels-Alder polymerization scheme.2•8 Tetraphenylcyclopentadienone (1) was chosen as the diene because it would provide adducts of moderately high molecular weight and because its versatility as a diene4 and as a comonomer2•8 in Diels-Alder reactions is well documented. The reaction of a vinylsilane (2) or ethynylsilane (3) with 1 afforded a 2,3,4,5-tetraphenylphenylsilane (4); a phenylethynylsilane (5) afforded a 2,3,4,5,6-pentaphenylphenylsilane (6); and an allylsilane (7) afforded a 2,3,4,5-tetraphenylbenzylsilane (8).

behavior. However, (F) almost has a monotonic behavior, the calculated value for NF2 being 0.003 au too small. The same problem occurs for , with only the calculated NF2 value preventing a monotonic increase across the series.In summary, then, most of the theoretical properties follow one of two patterns: (a) a monotonic increase or decrease across the series or (b) a potential curve-like behavior with maximum or minimum at CF2. The simplest understanding of these two patterns may be in the fact that the electron distribution may appear to behave differently, depending on the expectation value through which we observe it. For example, inspection of the (1/>a) values in Table V implies that the average distance of electrons from nu-cleus A decreases monotonically across the series. This behavior might be interpreted to imply that the "size" of the molecules decreases monotonically from BeF2 to OF2. Thus, the (1/>A) description of the electron distribution is consistent with properties of type a above. However, the calculated values of (r1 2) with respect to the center of mass show a different pattern, in which the molecular "size" decreases from BeF2 to CF2, but then increases at NF2 and again at OF2. We see that this picture of the electron distribution is harmonious with those properties following pattern b described above. We conclude that a major factor in determining the two patterns of periodic behavior for BeF2 through OF2 is the ambiguity involved in the concept of molecular size.

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