Monosilanol

Monosilanol is a silanol compound in which a silicon atom bearing three hydrocarbon substituents also carries a single hydroxyl group, giving the general formula R3Si–OH. This class is distinguished from other silanols that contain two or more hydroxyl groups (for example, disilanols such as R2Si(OH)2) and from higher silanol polymers. The simplest member is trimethylsilanol (Me3Si–OH); other common examples include triethylsilanol (Et3Si–OH) and triphenylsilanol (Ph3Si–OH).

Monosilanols are typically prepared by hydrolysis of chlorosilanes or alkoxysilanes, for example R3SiCl reacting with water to give R3Si–OH and HCl, or R3Si–OR' hydrolyzing to R3Si–OH and ROH. They can also arise as intermediates in the formation of higher-order siloxanes, and they may be generated in situ under controlled conditions for subsequent use.

Chemically, silanols are weak acids and can deprotonate to form silanolate species under basic conditions. A prominent tendency of monosilanols is to undergo condensation with another silanol to form disiloxanes (R3Si–O–SiR3) and water. This self-condensation can lead to cyclic or polymeric siloxane networks, which makes isolation of pure monosilanols challenging without stabilization (for example by bulky substituents).

Applications of monosilanols include use as intermediates in silicone and siloxane chemistry, where they serve as precursors to higher-order siloxanes and surface-modifying agents. They are mainly of interest in materials science and synthetic organosilicon chemistry, where controlled construction of Si–O–Si linkages is valuable. Safety data should be consulted for specific R groups, as monosilanols can be reactive toward moisture and air.