In the chemical industry, the direct process is a type of chemical reaction that makes organosilicon compounds by adding alkyl groups directly to pure elemental silicon. It is the most important process in organosilicon chemistry. The direct process is also called the Müller-Rochow process.
The most common application of the direct process is making dimethyldichlorosilane (DMDCS), the monomer used to make silicone. This reaction uses methyl chloride and a copper catalyst. The reaction is usually written
- 2 CH3Cl + Si → Si(CH3)nCl4−n
The n is used to show a mixture of five different products: tetramethylsilane Si(CH3)4, trimethylsilyl chloride Si(CH3)3Cl, DMDCS, methyltrichlorosilane, and silicon tetrachloride. The process also makes oligomers like Si2(CH3)4Cl2. These products need to be separated by fractional distillation.
