Propiolic acid

Propiolic acid, or acetylene mono-carboxylic acid, is an unsaturated organic acid prepared by boiling acetylene dicarboxylic acid, obtained by the action of alcoholic potash on dibromosuccinic acid, or its acid potassium salt with water. It forms silky crystals which melt at 6 °C, and boil at about 144 °C with decomposition. It is soluble in water and possesses an odor resembling that of acetic acid. Exposure to sunlight converts it into trimesic acid (benzene-1,3,5-tricarboxylic acid). Bromine converts it into dibromoacrylic acid, and it gives with hydrochloric acid O-chloracrylic acid. It forms a characteristic explosive silver salt on the addition of ammoniacal silver nitrate to its aqueous solution, and an amorphous precipitate which explodes on warming with ammoniacal cuprous chloride. Its ethyl ester condenses with hydrazine to form pyrazolone.