Vol. 60 acids were distilled helped to make the separation possible. Repeated fractionation of the fractions with high iodine number and high rotation finally gave an ethyl ester which had a constant boiling point (214°a t 10 mm.) and the theoretical iodine number. The specific optical rotation of this fraction was +55.4°. This same rotation was obtained from several fractions made by the above method. Boiling points were recorded by a calibrated millivoltmeter attached to a thermocouple at the top of the column. Reflux ratios of over six to one were maintained. The pressure was kept within less than 0.3 mm. by an automatic pressure regulator.Gorlic Acid.-After the constants of ethyl gorlate were obtained, the ester was saponified and the free acid liberated. After washing and drying, the acid was distilled at 10 mm. in the Podbielniak apparatus. It gave a horizontal distillation curve upon the first fractionation. About 20% decomposed, remaining in the distilling flask as a thick, dark brown liquid. The constants of pure gorlic acid were determined and are shown in Table III. Mol. weight, sample 0.1609 g.; 0.1 N potassium hydroxide 5.79 cc.; mol. wt., 277.8; caled., 278.2. Methyl Gorlate.-Gorlic acid was esterified with absolute methyl alcohol in the same manner as described above for the preparation of ethyl gorlate. A single distillation in the Podbielniak apparatus gave several fractions with identical constants and a horizontal distillation curve. The constants of methyl gorlate are given in Table III.
Since this acid was obtained only 70.5% pure we can determine its constants only from the curves made with the other pure homologs. These probable constants are shown in Tables II and III. Aleprolic Acid.-Fraction 49W, 1, Table I, clearly indicates the presence of this very low homolog of chaulmoogric acid. The boiling point of ethyl aleprolate should be 70°at 10 mm.; being impure it boiled slightly lower.The homolog between ethyl aleprestate and ethyl aleprolate should boil at 96°at 10 mm.It is probably present but our final fractions were too small to attempt further fractionation to prove its presence.An optically inactive unsaturated acid with one double bond must be present in fraction 50W, 2 to account for the iodine number found. There may also be present a saturated acid of low molecular weight.For purposes of comparison the constants of the other known optically active acids and their ethyl esters are included in Tables II and III.
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