The activated hydrogen such as hydroxyl group, amino group, carboxyl group, or amide group in the organic compounds can be substituted by silicon with the use of silylating agents. The purposes of substitution are as follows:

(1) To protect reactive group during chemical reaction
(2) To improve reaction selectivity
(3) To improve solubility in solvents
(4) To improve stability during distillation
(5) To improve applications for gas chromatograph and mass- spectrometry

At present, most uses are for the protection of the reactive group. Recently, many references have indicated preferential selectivity through use of a silylating agents. It is possible this application will gain more wide spread use in the near future. Silylating agents can protect against the reactive groups of alkaline reagents, oxidizing agents, reducing agents, Grignard reagents, and Wittig reagents used in the following processes.