Organohalosilanes are defined as RnSiX4-n (R is an organic functional group such as Me, Et, Pr, Ph, etc.; X is F, Cl, Br, I n = 1 to 3). Organohalosilanes are used for the preparation of silicone polymerization and other important silicon-functional silane materials. There are five methods for producing organohalosilanes:
- By using an organometallic compound as a medium for transporting organic groups, halogenated hydrocarbons can react with halosilanes to produce organohalosilanes.
- An organohalosilane is obtained from the addition reaction of a halogen-containing silane and an unsaturated hydrocarbon in the presence of catalyst.
- Hydrogen halides and halogenated hydrocarbons are subjected to a condensation reaction under heating to obtain organohalosilanes.
- The substituent groups in the silane are redistributed to obtain a new organohalosilane in the presence of the catalyst.
- The halogenated hydrocarbon is directly reacted with silicon under the condition of heating and existence of catalyst to obtain organohalosilane in one step.
Applications
Industry use: Organochlorosilanes are commonly used as coatings on silicon and glass surfaces, and also used in the production of silicone polymers. Chlorosilane analogues are quite common in sealants and adhesives sold to consumers and act as precursors for medical-grade silicones due to reduced toxicity. Reagents such as octadecyltrichlorosilane (OTS), perfluorooctyltrichlorosilane (PFOTCS) and perfluorodecyltrichlorosilane (FDTS) can be used in surface science and nanotechnology to form self-assembled monolayers. These fluorine-containing layers reduce surface energy and sticking. This effect is commonly used as a coating for MEMS and microfabricated stamps for nanoimprint lithography (NIL) and injection molding tools.
Chemical use: The hydrolysis of dichlorosilane can be carried out by putting the solution of H2SiCl2 into a large excess of water. Large-scale hydrolysis in a mixed ether/alkane solvent system at 0°C gives a mixture of volatile and non-volatile [H2SiO]n. The purpose of completing the hydrolysis of dichlorosilane is to collect the concentrated hydrolysate, distill the solution, and retrieve a solution of [H2SiO]n oligomer in dichloromethane. These methods are used to obtain cyclic polysiloxanes. Another purpose of hydrolyzing dichlorosilane is to obtain a linear polysiloxane, and it can be accomplished by many different complicated methods. The hydrolysis of dichlorosilane in the solvent of diethyl ether, methylene chloride or pentane produces cyclic and linear polysiloxanes.
