Organosilicon substituent steric effects

Most of the organosilicon compounds contain bonds between the silicon and carbon atom. In the following paragraph the structural chemistry of the Si—C single bond is discussed, mostly in compounds with tetracoordinate silicon and tetracoordinate carbon atoms. The structural chemistry of the Si—C bond in compounds where the carbon coordination state is different, is also discussed. The Si—C bond is markedly polarized and the increase of the bond ionicity by attaching different substituents to either the silicon or the carbon atoms may affect its length. The electronic and steric effects are discussed later. 

It is obvious from this table that the change of structure of the organosilicon compounds can have a more pronounced effect on the activation energy of chemical stage than on the heat of H complex formation. Moreover, steric effects of substituents at Si atom in these compounds have a more dominant role in the chemical interaction than in the complex stability. This is apparent from comparison of the Qajs change at adsorption of alkoxy-silanes with the observed chemisorption energies. The E., increases at enhancement (the absolute value) of a steric constant of the alkoxy substituent at Si atom. 

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