This section is from the book "The Volatile Oils Vol1", by E. Gildemeister. Also available from Amazon: The Volatile Oils.
When eugenol in heated with an excess of solid potassa,4) or in amyl alcoholic solution,5) or when eugenol potassium is heated to about 200 °6) with exclusion of air, it is converted into the isomeric Isoeugenol. This is also found in ylang-ylang oil and in oil of nutmeg. The following constants have been recorded:
B. p. 261° (not corr.);7) d18o 1,09; nDl,5680;8) B. p. Ill to 112° (3,5 mm.); d15o1,087 to 1,091; nD20o1,570 to 1,576; soluble in 5 to 6 vols, of 50 p. c. alcohol.9)
In a freezing mixture eugenol congeals to a mass of radiating needles which liquify at room temperature.10)
1) Wassermann, Jahresber. d. Chem. 1879, 520; Bertram and Gildemeister, Journ. f. prakt. Chem. II. 39 (1889), 354.
2) Comp. also Wallach and Rheindorff, Liebig's Annalen 271 (1892), 306.
3) Wallach, Liebig's Annalen 271 (1892), 307.
4) Einhorn and Frey, Berl. Berichte 27 (1894), 2455.
5) Tiemann, Berl. Berichte 24 (1891), 2870.
6) D. R. P. 179948.
7) Tiemann, Berl. Berichte 24 (1891), 2872.
8) Eykman, Berl. Berichte 23 (1890), 862.
9) Observations made in the Laboratory of Schimmel & Co. 10) Tiemann, Berl. Berichte 24 (1891), 2872.
Upon oxidation it yields vanillin, in the manufacture of which it is largely used.
For its identification the following compounds may be employed: monobromIsoeugenol dibromide, m. p. 138 to 139°; the acetyl derivative, m. p. 79 to 80°; the benzoyl derivative, m. p. 103 to 104°; and the diphenylurethane, m. p. 112 to 113°. In alcoholic solution Isoeugenol produces an olive-green color with ferric chloride, whereas eugenol produces a blue color.
 
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