Dichlorocarbene

Dichlorocarbene is a highly reactive chemical species with the formula CCl₂. It is a neutral molecule containing a divalent carbon atom with two chlorine atoms attached. Due to the electron-withdrawing nature of the chlorine atoms, the carbon atom is electron-deficient, making dichlorocarbene a strong electrophile. It is typically generated in situ, meaning it is produced immediately before it is used in a reaction, as it is too unstable to be isolated and stored.

Common methods for generating dichlorocarbene include the reaction of chloroform with a strong base, such as potassium tert-butoxide or sodium hydroxide under phase-transfer catalysis conditions. Another method involves the thermal decomposition of sodium trichloroacetate. Dichlorocarbene readily undergoes addition reactions with double bonds and insertion reactions into C-H and O-H bonds. It is a key intermediate in several important organic synthesis reactions, most notably the Reimer-Tiemann reaction, which is used to form aldehydes on phenolic rings, and the Simmons-Smith reaction, which is employed for cyclopropanation of alkenes. Its high reactivity also makes it a valuable tool in research and in the synthesis of various organic compounds.