Silicon compounds aromatic

Substituted aroyl- and heteroaroyltrimethylsilanes (acylsilanes) are prepared by the coupling of an aroyl chloride with (Me3Si)2 without decarbonylation, and this chemistry is treated in Section 1.2[629], Under certain conditions, aroyl chlorides react with disilanes after decarbonylation. Thus the reaction of aroyl chlorides with disilane via decarbonylation is a good preparative method for aromatic silicon compounds. As an interesting application, trimel-litic anhydride chloride (764) reacts with dichlorotetramethyidisilane to afford 4-chlorodimethylsilylphthalic anhydride (765), which is converted into 766 and used for polymerization[630]. When the reaction is carried out in a non-polar solvent, biphthalic anhydride (767) is formed[631]. Benzylchlorodimethylsilane (768) is obtained by the coupling of benzyl chloride with dichlorotetramethyl-disilane[632,633]. 

Acetyl hypofluorite is very effective m the fluorination of the aryl-metal (Hg, Ge, or Si) bond, but yields are frequently low. With aryl silicon compounds some competition exists for replacement of an aromatic hydrogen [5i, 52, 55, 54] (equations 25-27). Fluoroxytrifluoromethane fluorinates p-methoxypheny 1 mercuric acetate to givep-fluoroanisole in 86% yield [52]... 

Chlorinated aromatic hydrocarbons Volatile methyl-silicon compounds Methylcyclopentadienyl manganese (CO)3... 

Heterocyclic Sulfur Compounds with Two or More Rings Hexachlorobenzene under Ring-Substituted Aromatics Hexachlorobutadiene under Unsaturated Alkyl Halides Hexachlorocyclohexane Lindane under Saturated Alkyl Halides Hexachlorocyclopentadiene under Unsaturated Alkyl Halides Hexachloroethane under Saturated Alkyl Halides Hexadecane under Alkanes and Cyclic Alkanes Hexafluoroethane under Saturated Alkyl Halides Hexamethyldisihzane under Silicon Compounds—Other Significant Hexanes under Alkanes and Cyclic Alkanes Hexylamine under Primary Aliphatic Amines and Diamines... 

In this section we will discuss three families of neutral silicon compounds with potential three-dimensional aromaticity . 

Silicon compounds exhibit aromaticity and antiaromaticity in analogy to the corresponding carbon compounds. However, in general, the degree of their aromaticity and antiaromaticity is smaller than that of the analogous carbon compounds. 

The organopolysilanes are those compounds containing at least one silicon-silicon bond and one silicon-carbon linkage. This review is mainly concerned with the chemistry of aliphatic derivatives of polysilanes. Consideration of aromatic organopolysilanes is excluded from this review except as far as they are used as intermediates for synthesis and their properties correlate with the aliphatic silicon-silicon compounds, because the aromatic organopolysilanes have recently been well reviewed elsewhere (31,51, 73, 76a, 212). Physical properties of the polysilanes also are excluded from consideration except for spectral properties of ultraviolet absorption and nuclear magnetic resonance, since they are well summarized in earlier excellent reviews and texts (8, 34, 35, 51,131,132). 

It is known from electrochemical studies that fullerenes are easily reduced. Up to 6 electrons can be added reversibly [19], and, as mentioned earlier, the excited states are even more easily reduced. A large number of electron donors were investigated including aromatic and alkyl amines [29,43,79,119-140,152,161], ni-troxide radicals [57,117], suspensions of Ti02 [118], polyaromatic compounds, [19,127] organo-silicon compounds, [133,158] phenothiazine, [133] acridine [145,154], (3-carotene [141], tetrathiafulvalenes [146], tetraethoxyethene [147], phthalocyanines [148], porphyrines [151,153], NADH and analogues [150,154, 155], borates [156,159], and naphtoles [23] to name a few representative cases. 

Intramolecular complexes of penta-coordinate silicon formed by only one five-membered ring tre listed in Table 6. For identical substituents, the axial bound distances are longer than the equatorial ones and both are pronouncedly elongated in comparison with distances in tetravalent silicon compounds. A change in the covalent bond lengths upon the formation of the cycle points to the tendency to acquire an aromatic character. 

All the aromatic polyesters based on DEG have poor compatibility with blowing agents (pentanes or fluorocarbons) and to improve this compatibility compatibilising polyols such as ortho-toluene diamine polyols, propoxylated a-methyl glucoside polyols, oxyethylated p-nonylphenol, amine and amide diols, PO-EO block copolymers, borate esters, silicone compounds and so on, are frequently used [27-30]. 

TABLE 11. Partial rate factors for electrophilic aromatic substitution of some aromatic silicon compounds... 

TABLE 12. Relative rates and isomer distribution for chlorination of some silicon substituted aromatic compounds... 

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