tetrachloride

Tetrachloride refers to a chemical compound that contains four chlorine atoms. The most widely known member is carbon tetrachloride, CCl4, a colorless, dense, nonpolar liquid that historically served as a solvent and industrial intermediate.

Carbon tetrachloride has a tetrahedral molecular geometry and is relatively unreactive toward most acids. It boils at 76.7°C and melts at −22.9°C; it is immiscible with water and is not flammable under normal conditions. It is nevertheless photochemically active and can decompose to toxic products such as phosgene under light or heat.

Production typically involves the chlorination of methane: CH4 + 4 Cl2 → CCl4 + 4 HCl. In the past, CCl4 was widely used as a solvent, degreasing agent, and feedstock for the synthesis of other chlorinated compounds. It is also a precursor to phosgene, a toxic gas, which can form when CCl4 is exposed to light or heat in the presence of chlorine.

Health and environmental concerns led to strict regulation. CCl4 is hepatotoxic and possibly carcinogenic, and it is a potent ozone-depleting substance under the Montreal Protocol. Consequently its use is now limited largely to specific industrial applications or laboratory research, with strict containment and disposal requirements.

Other tetrachlorides exist for various elements. Examples include silicon tetrachloride (SiCl4), titanium tetrachloride (TiCl4), germanium tetrachloride (GeCl4), and tin tetrachloride (SnCl4). These compounds are typically reactive with water, often hydrolyzing to oxides or hydroxides and hydrogen chloride, and they find uses in synthesis, catalysis, and materials processing.