Silanol

Silanols are compounds containing silicon atoms to which hydroxy substituents bond directly. They are similar to alcohols just as silanes are similar to alkanes.

Silanols are named, when the hydroxy group is the principal one, by adding the suffix –ol to their mother name. If the hydroxy group is not the principal one, silanols are named by using the prefix hydroxy- according to the substitutive nomenclature. These rules are almost the same as those of alcohol, with the exception that silane is used as the mother hydride.

History

Silanols were first synthesized in 1871 by Albert Ladenburg. The first example was triethylsilanol. At that time, they were called silicols, a word that he coined.

Synthesis

Silanols are generally synthesized by hydrolysis of halosilane, alkoxysilane, or aminosilane; by oxidation of hydrosilane; or by hydrolysis of arylsilane in the presence of strong acid.

Properties

Silanols are generally dehydrated very easily, giving disiloxanes in the presence of acid, base, or even heat. Because of this property of self-condensation, the synthesis and isolation of silanols are difficult.

Silanols have hydroxy substituents, and so they have hydrogen bonding to each other in solution and even in crystals.

Silanols can also be crosslinked using borax, or boric acid, to form 3-dimensional silicon gels.

Silanols exist not only as chemical compounds but also on the surface of silica. From the viewpoint of organometallic chemistry, silica can be considered as an enormous ligand, and it is used as supports for catalysts of many reactions. In chromatography, derivitization of accessible silanol groups in a bonded stationary phase with trimethylsilyl groups is referred to as endcapping.

See also

• Trimethylsilanol
• Diphenylsilanediol
• Organosilicon