Silanes and Related Compounds

Some of the interesting features in silanes which are well reproduced by the calculations include the rotational barriers (T7 kcal mole-1 in methylsilane as compared with 2-9 kcal mole-1 in ethane, and correspondingly low numbers for other methyl silanes). While the torsional function about the 2,3-bond in 1-sila-butane looks almost like that in butane, the corresponding function 

For silacyclohexane, the chair conformation is calculated to be the lowest in energy, as with cyclohexane, but because of the rather small torsional barrier about C—Si bond, the C2 twist-boat con-former is only 3 kcal mole-1 higher (no experimental value). The barrier to the chair-chair inversion is also lower than in the hydrocarbon (for 1,1-dimethylsilacyclohexane, the calculated (Tribble and Allinger, 1972 Ouellette, 1974) and observed (Jensen and Bushweller, 1968) values are respectively 5 46 and 5 5 kcal mole-1). 

2-Butanone and other straight chain homologs were examined, and it was calculated that the carbon skeleton prefers an all anti conformation gauche forms are higher in energy, but as with hydrocarbons, not by very much. For 2-butanone, both the structure and the conformational equilibrium were well reproduced (Abe et al., 1969 Pierce et al., 1969). 

Cyclobutanone has been studied by microwave spectroscopy, and the experimental structure is shown in Fig. 5 (Scharpen and Laurie, 1968 see also, d Annibale and Lunazzi, 1973). The corresponding calculated numbers are given in parentheses. The experimental 

Cyclohexanone has been studied in some detail. Early hand calculations on this molecule suggested (Eliel et al., 1965, p. 186) that the relative energies of the boat forms and the barrier to the chair-chair inversion would be smaller in cyclohexanone than in 

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Over the past few years significant progress has been made in replacing trialkylstannanes as radical generating reagents and hydrogen atom donors. Some aspects, such as the use of silanes and related compounds, and of cyclohexadienes have been reviewed recently and will not be covered here [1-5]. 

TABLE 22. Reduction potentials of (iodomethyl)silanes and related compounds ... 

TABLE 3. carbonyl group chemical shifts (5 ) of selected acyl silanes and related compounds"... 

Alkenylsilanes, mainly vinyl silanes and allyl silanes or related compounds, being widely used intermediates for organic synthesis can be efficiently prepared by several reactions catalyzed by transition-metal complexes, such as dehy-drogenative silylation of alkenes, hydrosilylation of alkynes, alkene metathesis, silylative coupling of alkenes with vinylsilanes, and coupling of alkynes with vinylsilanes [1-7]. Ruthenium complexes have been used for chemoselective, regioselective and stereoselective syntheses of unsaturated products. 

In contrast to pyridine, isoquinoline, acridine and related compounds which fail to undergo ionic hydrogenation1, Hantzsch-type 1,4-dihydropyridines 1 are conveniently reduced by tri-ethylsilane/trifluoroacetic acid to yield the all-nww-isomers of 1,2,3,4-tetrahydropyridines 2 and piperidines 311. The steric course of the reduction is a function of the temperature and the amount of silane used. 

The known reactions of the hydroxy function in the carbon moieties of phosphonic acids and related compounds are many. When treated with an excess of a silane, RsSiH, in the presence of colloidal nickel at about 110 °C, (hydroxymethyl)phosphonic and bis(hydrox-ymethyl)phosphinic acids each undergo silylation at both alcohol and acid OH sites, although equation 12 is a simplification of the overall chemistry. The other main phosphorus-containing product from such reactions is 198 (when R = Et) the 1,4,2,5-dioxadiphosph(V)orinanes (199) are also isolable if reaction product mixtures are kept at ambient temperature. An excess of an alkoxysilane R3SiOR also fully silylates... 

Group-transfer polymerization (GTP) was discovered by scientists at DuPont and involves the conjugate Michael addition of an enol silane or related compound to acrylate or methacrylate monomers under the influence of an activator. The process is related to anionic polymerization but the species involved are believed to feature a high degree of covalent character in the transition state for chain growth. 

D. DIENE DIMERIZATION WITH INCORPORATION OF SILANES, DISILANES, AND RELATED COMPOUNDS... 

Chlorine reacts violently or explosively with a wide range of substances, including hydrogen, acetylene, many hydrocarbons in the presence of hght, ammonia, reactive metals, and metal hydrides and related compounds, including diborane, silane, and... 

Most of the strong deviations between predictions and experiment are due to less common functional groups like silanes or fluorocompounds or due to high symmetry like adamantane and related compounds, which is difficult to cope with via a non3D... 

Bueche and Oliver contacted vapors of an organophilizing silane with the freshly made silica at 150-500 C as it cooled (536). Treatment of silica with vapors of (CHs),SiO(CH3) and related compounds with 1% of an amine catalyst such as butylamine can be continued in a closed container for 2 weeks at ordinary temperature to obtain good surface coverage. The product is used in polysiloxane elastomers as a reinforcing filler (537). 

Virtually all treatments in commercial use are chosen to chemically bond an organic species to the filler surface, thus improving compatibility with organic polymers. The most common functionalities used for this are acids or acid precursors, such as anhydrides (for basic or amphoteric fillers) and alkoxy-silanes (for fillers with metal hydroxyls present, especially siliceous fillers). Organo-titanates and related compounds are also proposed for nse with a wide variety of fillers. 

Examples of well-known PISs working under laser lights in this blue-green area include the Eosin/amine, Eosin/amine/bromo compound, ketocoumarin/amine/iodonium salt, thioxanthene dye/amine/iodonium salt, erythrosin/amine, julolidine dye/Cl-HABEthiol, cyanines and related compound/borate/additive systems, pyrromethine/amine/triazine or styryl naphtothiazole dye/Cl-HABEthiol systems and Cl-HABI-based systems. A lot of novel Dye/iodonium salts/silanes can also work (e.g. [XIA 15] see sections 1.3.5 and 1.3.6). 

Reactions of Silane I and Related Compounds. Silane I was prepared by reacting two equivalents each of acrylic acid and tiiethylamine for each equivalent of chloromethyldimethylchlorosilane. When only one equivalent each of the acid and amine was used, an intermediate silane was isolated. Although... 

Anotlier important modification metliod is tire passivation of tire external crystallite surface, which may improve perfonnance in shape selective catalysis (see C2.12.7). Treatment of zeolites witli alkoxysilanes, SiCl or silane, and subsequent hydrolysis or poisoning witli bulky bases, organophosphoms compounds and arylsilanes have been used for tliis purjDose [39]. In some cases, tire improved perfonnance was, however, not related to tire masking of unselective active sites on tire outer surface but ratlier to a narrowing of tire pore diameters due to silica deposits. 

This section concerns TgPhg and its derivatives formed by reactions on the phenyl rings. For other related compounds prepared from hydrolysis of the corresponding silanes (e.g., Tgftolyllg) see the miscellaneous Section V.I. 

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