Butanethiol is chemically classified among the thiols, which are organic compounds with molecular formulas and structural formulas similar to alcohols, except that sulfur-containing sulfhydryl group (-SH) replaces the oxygen-containing hydroxyl group (-OH) in the molecule. Butanethiol's basic molecular formula is C4H9SH, and its structural formula is similar to that of the alcohol n-butanol. Butanethiol is prepared by the free radical catalyzed addition of hydrogen sulfide to 1-butene. Commercially, this is performed using ultraviolet light. Butanethiol is a thiol of low molecular weight, and it is highly flammable.