Skatol, B-methylindol, has thus far been found in civet and in the wood of Celtis reticulosa, also in a wood1) obtained from German East Africa. It crystallizes in white laminae which melt at 95° and boil at 265 to 266° and which possess a strong fecal odor. The hydrochloride, 2C9H9NHC1, melts at 167 to 168°. The picrate crystallizes from benzene in dark red, shiny needles, m. p. 172 to 1730.2) The solution of p-dimethylaminobenzaldehyde is colored blue by skatol.3) Like indol, skatol is used in the preparation of artificial floral perfumes.
1) Report of Schimmel & Co. April 1903, 79.
2) Observations made in the laboratory of Schimmel & Co.
3) Weehuizen, Pharm. Weekblad 45 (1908), 1325; Steensma, Zeitschr. f. physiol. Chem. 47 (1906), 25; Gautier and Noyer, Compt. rend. Soc. biol. December 19th 1908; abstr. in Bull. Soc. chim. IV. 5 (1909), 256. Comp. also Repoit of Schimmel & Co. April 1909, 140; October 1909, 213.
Among the basic constituents of volatile oils the methyl ester of anthranilic acid should be mentioned. It was discovered in 1895 by Walbaum in neroli oil and has since been found in the oils of tuberose, champaca flowers (?), ylang-ylang, Spanish orange blossoms, sweet orange rind, West Indian limette (?), ber-gamot leaves, jasmin flowers, and gardenia, judging from the odor, this ester is likewise contained in the flowers of Lathyrus odorata, Robinia Pseudo-Acacia, Philadelphus Coronarius and of several species of apples. Artificially it is readily obtained by passing hydrogen chloride into the methylalcoholic solution of anthranilic acid.
The methyl ester of anthranilic acid forms large crystals with numerous faces. Both crystals and solution, especially the alcoholic solution, reveal a beautiful fluorescence. Molten, it remains liquid for a long time, even at low temperature. The odor of the ester as such is not especially agreable, but characteristic. Diluted, it reminds of the odor of. orange blossoms. The constants of the compound isolated from neroli oil are:
Congealing point 24°; m. p. 24 to 25°; b. p. 132° (14 mm.); d16o 1,168 (in the supercooled condition).1).
The ester is readily soluble in alcohol, ether and dilute inorganic acids, fairly readily in water and is volatile with water vapor.
Of its derivatives the following should be mentioned. The picrate crystallizes in yellow needles that melt at 103,5 to 104°.2) The thiophenyl ketotetrahydroquinazoline results quantitatively when anthranilic acid methylester is heated with phenyl mustard oil to from 100 to 120°. This compound is readily soluble in caustic soda solution, very difficultly in alcohol. It melts above 300° but sublimes at 160 to 170°.
From volatile oils the ester can readily be separated by shaking with dilute sulphuric acid. The sulphate crystallizes out in the cold, can be purified by recrystallization from alcohol, and is decomposed by means of soda.3)
1) Walbaum, Journ. f. prakt. Chem. II. 59 (1899), 352.
2) Freundler, Bull. Soc. chim. III. 31 (1904), 882. In the laboratory of Schimmel & Co. 105 to 106° were observed.
3) Walbaum, Loc. cit.
Hesse and Zeitschel1) utilized the sulphate for the quantitative determination of the ester. They proceeded according to the following method:
About 25 g. of the oil to be examined are dissolved in twice or thrice the amount of dry ether. In a freezing mixture the temperature is reduced to at least 0°. Amidst constant stirring a solution of 1 vol. of concentrated sulphuric acid in 5 vols, of ether is added drop by drop until no further precipitate is produced. The precipitate is collected on a filter and washed with dry ether until it is odorless. It is then dissolved in water, if necessary with the aid of alcohol, and, without previous filtration,2) is tritated with half normal caustic alkali. If for s grams of oil a ccm. of alkali are used, the percentage of ester in the oil equals a • 3,775 / s
To the solution an excess of half normal alkali is now added and the mixture heated on a water bath for half an hour. The amount of alkali not used for saponification is titrated back with half normal sulphuric acid. The percentage of ester is computed according to the following formula: b • 7,55 / s in which b represents the amount of half normal alkali used for saponification, a should be again as large as b.
This method not only determines anthranilic acid methyl ester, but other basic substances as well (methylanthranilic acid methyl ester). In order to avoid this, E. Erdmann3) has suggested another method in which he utilizes the property of the ester as primary base to form azodyes. The ester is shaken out of the oil with either dilute sulphuric or dilute hydrochloric acid; the acid solution is diazotized with a 5 p. c. solution of sodium nitrite, and titrated with an alkaline solution of /i-naphthol (0,5 g. B-naphthol in a solution of 0,5 g. of caustic soda and 15 g. sodium carbonate in 150 ccm. of water). The insoluble dyestuff is precipitated and the end of the reaction ascertained by testing a drop removed from time to time. According to Hesse and Zeitschel,1) the method of Erdmann suffers from the fact that the isolation of the ester is not a quantitative one. In order to obtain satisfactory results the ester should be isolated as sulphate as described above. For the rest either the one or the other method can be followed. If anthranilic acid methyl ester and methylanthranilic acid methyl ester are to be determined side by side it is advisable to combine both methods.
1) Berl. Berichte 34 (1901), 296.
2) Hesse and Zeitschel, Journ. f. prakt. Chem. II. 64 (1901), 246, footnote.
3) Berl. Berichte 35 (1902), 24.
Methylanthranilic acid methyl ester.
Methylanthranilic acid methyl ester occurs in mandarin oil, also in mandarin leaf oil and possibly also in oil of rue. Like the anthranilic acid methyl ester, it shows a blue fluorescence, as such as well as in solution. The constants of the ester isolated from mandarin oil are as follows:
M. p. 18,5 to 19,5°; b. p. 130 to 131° (13 mm.); d15o1,120.2)
In connection with a synthetic product containing 98 p. c. of ester, Schimmel & Co. observed the following constants:
Congealing point 17,8°; m. p. 18°; d20O 1,1238; aD + 0°; nD20o 1,57963; soluble in 10 vol. of 70 p. c. and in 3 vol. of 80 p. c. alcohol.
For further characterization the saponification products can be utilized. Methylanthranilic acid crystallizes from alcohol in white prisms which melt at 179° and which reveal a blue fluorescence in solution.
1) Berl. Berichte 35 (1902), 2355.
2) Walbaum, Journ. f. prakt. Chem. II. 62 (1900), 136.