PIPERONAL (heliotropine, protocatechuic aldehyde methylene ether), C 8 H 6 O3, an aromatic aldehyde. It is prepared by oxidizing piperic acid with potassium permanganate (R. Fittig, Ann., 1869, 152, p. 35); by condensing methylene iodide with protocatechuic aldehyde (R. Wegscheider, Monats., 1893, 14, p. 388) ; or by oxidizing isosafrol with chromic acid. It forms long colourless crystals which melt at 37 C. and boil at 263 C. It has an agreeable smell, resembling that of heliotrope, and is much used in perfumery. It is only slightly soluble in cold water, but is readily soluble in alcohol and in ether. When heated with dilute hydrochloric acid to 200 C. it yields protocatechuic aldehyde, C 7 H 6 O3, and carbon. It readily combines with sodium bisulphite and with various bases (ammonia, aniline, methylamine, etc.).
Note - this article incorporates content from Encyclopaedia Britannica, Eleventh Edition, (1910-1911)