Methyl chloride (CH3Cl) or monochloromethane is a colourless gas with an ethereal odour that is heavier than air. It is also known as R-40.
It is used in the chemical industry as a methylation agent in organic synthesis in the manufacture of tetramethyl lead, silicones and butyl rubber, as a solvent or extraction agent for heat-sensitive products, as a refrigerant and as a propellant.