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.