Chloromethanal

Chloromethanal, also known as formyl chloride, is a chemical compound with the formula HCOCl. It represents the formyl derivative of hydrogen chloride and is the simplest acyl halide derived from formaldehyde. The molecule consists of a formyl group (H-C(=O)) bonded to a chlorine atom.

Chloromethanal is highly reactive and volatile; at room temperature it exists predominantly as a gas and is usually not isolated. It hydrolyzes readily in the presence of water to formic acid and hydrogen chloride: HCOCl + H2O → HCO2H + HCl. Because of its instability, it is typically generated and consumed in situ in synthetic reactions rather than stored.

Preparation and handling: In practice, chloromethanal is produced in situ by chlorinating formaldehyde under strictly anhydrous conditions, or by reagents that generate formyl chloride in situ. The compound is moisture-sensitive and reacts with many nucleophiles; reactions are typically conducted under inert atmosphere and in dry solvents.

Uses: It serves mainly as an intermediate in organic synthesis, particularly as a formylating agent in limited or specialized contexts. Its reactivity makes it a useful building block for generating formylated products, but its handling requires caution due to instability and toxicity.

Hazards: Formyl chloride is highly toxic and corrosive. It is a lachrymator and reacts with water to release formic acid and hydrogen chloride. It can cause respiratory and eye irritation and must be used only in well-ventilated fume hoods with appropriate protective equipment.