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Part 9

Wild Volatile-Oil Plants and Their Economic Importance · Frank Rabak — chapter 9 of 12 · ~2,053 words · public domain

COMBINED ACIDS.

As stated previously, the oil was found to contain a small percentage of esters, or organic acids in combination with higher alcohols. In order to identify these acids, which are in combination in the form of esters, a quantity of the oil, after removing the free acids, was saponified by heating on a water bath for half an hour with a slight excess of alcoholic potassium hydroxid. The mixture, after saponification, was diluted with water and the unsaponified oil separated. The alkaline liquid, which now contained the combined acids as their potassium salts, after being freed from adhering particles of oil by shaking with ether, was acidified with sulphuric acid and distilled with steam. The insoluble oily acids which formed on the distillate were separated by shaking the distillate lightly with ether and evaporating the ether.

SOLUBLE COMBINED ACIDS.

The aqueous portion of the distillate which contained the soluble combined acids of the oil was neutralized with barium carbonate, concentrated and precipitated with silver nitrate solution. Only a small precipitate resulted. This precipitate was found to contain 55.9 per cent of silver, which corresponds to silver butyrate. Hence the acid in the distillate was butyric acid.

INSOLUBLE COMBINED ACIDS.

As heretofore stated, the insoluble oily acids obtained by extraction with ether were carefully neutralized with potassium hydroxid solution and precipitated fractionally with silver nitrate. Two precipitates were obtained which were thoroughly washed and dried. The first and largest precipitate assayed 51.2 per cent silver, the second assaying 45.1 per cent silver. This would indicate that the insoluble acids were valerianic acid (silver valerianate requiring 51.6 per cent silver), and heptoic acid (silver heptoate requiring 45.5 per cent silver), the valerianic acid predominating.

The results show that the esters of this oil exist as the salts of butyric, valerianic, and heptoic acids, valerianic acid esters, however, predominating.

FRACTIONATION OF THE OIL AND SEPARATION OF THE STEAROPTENE.

For the purpose of accomplishing a separation of the constituents, 50 grams of the oil, after saponification, were dried and subjected to fractional distillation in a three-bulb Ladenburg flask. The results are given in Table V.

+Table V.+--Fractionation of saponified oil of swamp bay and description of fractions.

Beginning with fraction 6 each successive fraction was refrigerated in a freezing mixture of ice and salt and the crystals separated by centrifuging in a platinum Gooch crucible. A total of 13.7 per cent of crystals was obtained.

In order to obtain a further separation of crystals the portions of the oil beginning with fraction 5 were fractionated into the following fractions: 190° to 195° C.; 195° to 200° C.; 200° to 205° C.; 205° to 215° C.; 215° to 233° C.; 233° to 260° C. A total of 4 per cent of crystals was obtained by refrigeration and centrifugation of those fractions in which crystals appeared. The portion between 190° and 215° C., and also fraction 4 of the original, were further fractionated into four parts: 185° to 190° C.; 190° to 195° C.; 195° to 205° C.; 205° to 215° C., an additional yield of 3.3 per cent of crystals being obtained.

By the above method of successive fractionation and refrigeration a total of 21 per cent of crystals was obtained from the oil. This represents only approximately the total percentage of stearoptene in the oil. The separation was not at all quantitative, as a considerable proportion was lost in the manipulations incident to the separation. Since the quantity of oil at hand was so meager the fractions were reduced to such small quantities that further separation of crystals was impossible, and as unavoidable losses were encountered in transferring to and from the centrifuge the final percentages were materially affected and the true amount of stearoptene may be assumed to be considerably more than is shown above.

After the fractionation and refractionation of the oil and the separation of the stearoptene portion, the remaining elaoptene portion grouped itself into fractions, whose physical properties were determined and qualitative tests for their constituents applied, as shown in Table VI.

+Table VI.+--Refractionation of the oil of swamp bay, showing the physical properties of the fractions.

---------+------------+-------------+-------------+-----------+---------------- | | Specific | Rotation |Re-fraction| Fraction.|Temperature.| gravity | in 50 mm. | N{D} | Tests applied. | | at 25° C. | tube. | 25°. | ---------+------------+-------------+-------------+-----------+---------------- |Degrees C.| | Degrees._ | | 1 |Below 170 |Insufficient.|Insufficient.| 1.4648 | When shaken | | | | |with water the | | | | |aqueous solution | | | | |strongly reduced | | | | |magenta solution | | | | |to violet color; | | | | |also produced | | | | |silver mirror | | | | |with ammoniacal | | | | |silver nitrate. 2 |170 to 182 | 0.9011 | +22.5 | 1.4630 | Iodol | | | | |(tetraiodopyrol) | | | | |dissolved in oil | | | | |by gentle | | | | |warming yielded | | | | |yellow crystals | | | | |melting at | | | | |115° C.; cineol | | | | |iodol melts at | | | | |112° C. 3 |182 to 185 | .9012 | +21.5 | 1.4628 | Treated with | | | | |iodol and the | | | | |yellow crystals | | | | |recrystallized | | | | |from benzol | | | | |melted sharply | | | | |at 112°. 4 |185 to 190 | .9075 | +23 | 1.4628 | Cineol-iodol | | | | |crystals melted | | | | |at 113° C. 5 |190 to 205 | .9228 | +31 | 1.4653 | Do. 6 |205 to 215 | .9351 |.............| 1.4706 | Negative test | | | | |with iodol. 7 |215 to 233 | .9358 |.............| 1.4765 | Do. 8 |233 to 260 | .9360 |.............| 1.4830 | Oxidized with | | | | |3 per cent | | | | |potassium | | | | |permanganate | | | | |in cold yielded | | | | |camphor | | | | |crystals. ---------+------------+-------------+-------------+-----------+----------------

IDENTIFICATION OF THE CONSTITUENTS OF THE OIL.

Camphor.--The compound obtained from the oil by refrigeration was a soft, white, granular, crystalline mass, and possessed a distinct camphorlike odor and slightly bitter camphoraceous taste. The crystals sublimed readily and melted at 174° to 176° C. The boiling point of the compound was 205° C., and the rotation in a 50 mm. tube of 20 per cent solution in alcohol was found to be +3.8°, 20 percent solution of commercial camphor in alcohol rotating +3.5°. It was readily soluble in alcohol and the other organic solvents.

To further identify the crystals with ordinary camphor two compounds were prepared, the semicarbazone and the oxime, with which camphor forms definite chemical compounds. The semicarbazone was prepared according to the method of Tiemann. (See p. 17.) The crystals obtained after recrystallization from alcohol melted at 237° to 239° C., pure camphor semicarbazone melting at 236° to 238°. For the preparation of the oxime Auwers’ method was applied. (See p. 16.) Recrystallized from ether the oxime melted at 117° to 118° C., whereas pure camphor oxime melts at 118° to 119° C.

Since the physical and chemical properties of this substance correspond almost identically with those of camphor, it may be safely stated that the crystals are those of commercial dextro camphor.

Aldehyde constituent.--From the pungent and penetrating odor and the strong reducing properties of the first fraction, which, as shown in Table V, distilled largely below 80° C., there would seem to be the possible presence of a trace of formaldehyde.

Cineol, or eucalyptol.--Qualitative tests as indicated in Table V show the presence of cineol in fractions from 170° to 205° C., the characteristic crystalline cineol addition product of iodol corresponding in melting point to the pure cineol iodol. Cineol was further identified in these fractions by the preparation of cineol hydrobromid prepared by passing dry hydrobromic acid gas into a well-cooled solution of the oil in petroleum ether. A crystalline hydrobromid was obtained from each fraction which gave the iodol reaction. The hydrobromids prepared melted between 55° to 57° C., while pure cineol hydrobromid is reported as melting at 56° to 57° C.

Since the presence of cineol in the several fractions of the oil was proved, a quantitative estimation was deemed desirable. Because of the smallness of the individual fractions the hydrobromic acid method was adopted in this estimation, it being the most accurate when cineol is present in only small quantities. The phosphoric acid method is best adapted to oils which are very rich in the compound. The hydrobromic acid method has been used in the assay of eucalyptus oils, and consists essentially in conducting dry hydrobromic acid gas into a solution of the oil in about twice its volume of petroleum ether, the solution being well cooled by a freezing mixture, separating the crystals on a force filter, washing and decomposing with water, and measuring the cineol formed. A slight deviation was made from the directions on account of the smallness of the fractions and consequently the small amount of hydrobromid obtained, which when decomposed with water would introduce an error. After the hydrobromid of cineol was obtained in each case and washed it was weighed and the percentage of cineol was calculated from the weight of the crystals from a given quantity of each fraction. In this manner by assaying the four fractions which gave qualitative tests there was found to be a total of 19.8 per cent of cineol in the oil.

Borneol.--By oxidation of fraction 233° to 260° C. with a 3 per cent solution of potassium permanganate, slightly warming and allowing it to stand for 12 hours, then shaking out the mixture with ether and allowing the ether to evaporate, a mass of crystals remained which proved to be camphor. It is possible that borneol was present in this fraction, as borneol is readily oxidized to camphor with ordinary oxidizing agents. Since the preliminary chemical examination of the oil indicated a small percentage of esters and of free alcohol, the alcohol was probably borneol.

SUMMARY.

From the results obtained in the chemical examination it appears that the oil of swamp bay contains over 21 per cent of camphor, 19.8 per cent cineol, and borneol, the latter possibly occurring to a small extent as esters and as the free alcohol. No terpenes were identified. Since only a very small portion of the oil distills over below 175° C., it would seem that the oil is not terpenic in character, as most members of the terpene group of hydrocarbons boil below 175° C.

Besides the constituents mentioned, the oil contains butyric acid in free condition to a slight extent; butyric, valerianic, and heptoic acids combined in the oil as esters, valerianic acid predominating, and a slight trace of an aldehyde, possibly formaldehyde.

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