Anisic aldehyde (p-methoxy benzaldehyde), also known as aubepine, results upon oxidation of anethol. Hence it is found in old, anethol-containing oils, such as anise oil, staranise oil and fennel oil. Its presence has likewise been demonstrated in the extract of Tahiti vanilla, and in Roman and French cassie blossom oils. The odor of the flowers of Crataegus Oxyacantha, Pyrus communis, Sorbus Aucuparia, Viburnum Tinus, and Erica arborea, would seem to indicate1) that anisic aldehyde is contained in them, but as yet no chemical proof has been brought forward.
Artificially, anisic aldehyde is prepared by the oxidation of anethol by means of nitric acid or chromic acid mixture, or by methylation of p-hydroxy benzaldehyde. When purified by means of the acid sulphite addition product, anisic aldehyde is a colorless liquid which boils at 248° (corr.).2) Its odor resembles that of the flowers of Crataegus Oxyacantha. The properties of anisic aldehyde, as prepared on a large scale, have been determined by Schimmel & Co.:
B. p. 91° (4 mm.); d15o1,126 to 1,129; aD + 0°; nD20o 1,572 to 1,574; soluble in 7 to 8 vols, of 50 p. c. alcohol. The aldehyde can be characterized by means of its oxidation to anisic acid
1) Report of Schimmel & Co. October 1903, 20; Verschaffelt, Chem. Weekblad 1908, No. 25, 1; Report of Schimmel & Co. October 1908, 161. 2) Perkin, Journ. chem. Soc. 69 (1896), 1200.
(m. p. 184°) into which it passes over when improperly kept. Furthermore, by means of its semicarbazone (m. p. 203 to 204°), or of its oximes, of which one modification melts at 63°, the other at 132o.