Anethol (p-propenylanisol), C10H12O, is the principal constituent of anise and staranise oils and is an important constituent of fennel oil. Its presence in the oil of Osmorrhiza longistylis and in kobuschi oil has likewise been demonstrated. It is usually obtained from anise oil, staranise oil or fennel oil, ether by freezing the oils themselves or the corresponding fractions. Synthetically it has also been obtained in several ways.
1) Grimaux, Compt. rend. 117 (1893), 1091.
2) Eykman, Berl. Berichte 23 (1890), 862.
3) Bertram and Walbaum, Arch, der Pharm. 235 (1897), 179, 182.
4) Hell and Gaab, Berl. Berichte 29 (1896), 344.
Anethol constitutes a white, crystalline mass with an odor of anise and with an intensely sweet taste. It melts to a colorless, optically inactive, strongly refractive liquid. The following properties have been recorded:
M. p. 21°; d25o0,986; nD18o 1,56149;1) d11.5o0,999; nD 1,5624.2)
In connection with anethol produced on a large scale, Schimmel & Co. observed the following values:
Of characteristic bromine derivatives of anethol, the anethol dibromide, C6H4OCH3C3H5Br2, m. p. 67°,3) and the monobrom anethol dibromide, C6H3BrOCH3C3H6Br2, m. p. 107 to 1087) may be mentioned. These are formed by the action of bromide on anethol under varying conditions. By the action of alcoholic potassa on anethol dibromide in the cold, anethol glycol, C6H4OCH3C3H5(OH)2,5) results. When acted upon with 20 p. c. sulphuric acid, this is converted to anise ketone. The same glycol is likewise formed by the action of mercuric acetate upon anethol.6) Anethol nitrite, C10H12O.N2O3, m. p. 121°, and anethol nitrosochloride, C10H12ONOC1, m. p. 127 to 128°, should also be mentioned.
Dilute nitric acid oxidizes anethol to anisic aldehyde, chromic acid oxidizes it to anisic aldehyde and anisic acid, potassium permanganate to /Mnethoxyphenylglyoxylic acid C6H4.(OCH3)CO •COOH, m. p. 89°, the oxime of which melts at 145 to 146°.
1) Stohmann, Sitzungsber. d. Akad. d. Wiss. Leipzig 1892, 318.
2) Eykman, Berl. Berichte 23 (1890), 862.
3) Hell and v. Gunthert, Journ. f. prakt. Chem. II. 52 (1895), 198.
4) Hell and Garttner, Journ. f. prakt. Chem. II. 51 (1895), 424; Hell and v. Gunthert, loc. cit. 194.
5) Varenne and Godefroy, Compt. rend. 140 (1905). 591. 6) Balbiano and Paolini, Bed. Berichte 35 (1902), 2997.
When acted upon by light and air,1) anethol gradually loses its capacity to crystallize and finally no longer even congeals. At the same time it becomes viscid, acquires a yellow color and an unpleasant, bitter taste, both of which no larger remind of anise. This change is accompanied by an increase in the solubility and an increase in specific gravity which may rise above 1. These phenomena are attributed to the formation of oxidation2) (anisic aldehyde, anisic acid) and other products. Of the latter de Varda3) has isolated a compound named photoanethol which he regards as a polymer of anethol. According to Hoering and and Gralert,4) de Varda's interpretation is not correct, but photo-anethol is regarded as identical with di-p-methoxystilbene. This substance is characterized by its insolubility and is possibly the cause of the turbidity produced in freshly prepared anethol upon standing.
Recrystallized from glacial acetic acid and benzene, di-p-me-thoxystilbene is obtained in shiny leaflets that melt at 214 to 215°, which show a blue fluorescence both in the solid condition and in solution. Probably di-p-methoxystilbene is not formed directly from anethol but from the intermediate anisic aldehyde.
p-Hydroquinone ethyl ether.
p-Hydroquinone ethyl ether (p-hydroxyphenetol), C8H10O2, occurs in small amount in staranise oil. It can be obtained synthetically by boiling p-diazophenetolsulphate with dilute sulphuric acid,1) or from hydroquinone by heating it with ethyl iodide and potassium hydroxide using a reflux condenser.2)
1) According to Grimaux anethol also looses its capacity to crystallize upon prolonged heating. Bull. Soc. chim. III. 15 (1896), 778.
2) Report of Schimmel & Co. October 1904, 11.
3) Gazz. chim. ital. 21 (1891), 183; Chem. Zentralbl. 1891, I. 788.
4) Berl. Berichte 42 (1909), 1204.
The synthetic product consists of thin leaflets with satiny lustre, which are readily soluble in hot water, melt at 66° and boil at 246 to 247°.