How do haloforms form dihalocarbenes?

Dihalocarbenes are formed from haloforms ($HC{X}_3$, where $X$ is chlorine, bromine, or iodine) through an ionic reaction involving a strong base, such as potassium tert-butoxide.1

The process occurs in two primary steps:

• Deprotonation: The strong base removes a proton (hydrogen ion, $H^{+}$) from the haloform molecule in an acid-base reaction, resulting in the formation of a trihalomethide ion (e.g., potassium trichloromethide).1
• Elimination: The resulting trihalomethide ion subsequently loses a halide salt (such as potassium chloride) to yield the corresponding dihalocarbene.1

This method is a classic example of generating carbene intermediates through ionic pathways rather than through the photolysis or pyrolysis of precursors like diazo compounds.1