Resolution of the alpha-beta-dihydroxy-alpha-methyl-beta-isopropyladipic acids / by T.A. Henry and H. Paget.

  • Henry, Thomas Anderson, 1873-1958
Date:
[1923.]
Catalogue details

Licence: Public Domain Mark

Credit: Resolution of the alpha-beta-dihydroxy-alpha-methyl-beta-isopropyladipic acids / by T.A. Henry and H. Paget. Source: Wellcome Collection.

    7/16 (page 1882)
    189°, from the a-terpinene present in chenopodimn oil has been described already (loc. cit.). The yield from 1,000 c.c. of the hydro¬ carbon fraction of the oil, which probably contains about 1G per cent, by volume of a-terpinene, is about 16 grams of the crude crystalline acids, from which, on recrystallisation from boiling water, about 10 grams of the high-melting and about 5 grams of the low-melting form are eventually obtained. (6) By synthesis from dimeihylacetonylacetone. The dimethyl- acetonylacetone (b. p. 209—212°/751 mm.) was prepared from methylheptenone made by Verley's method from citral (Bull. Soc. chim., 1897, [iii], 17, 175). The yield of the diketone, expressed on the citral used, was about 21 per cent. After preliminary trials, the following method was found to give the best yield of the required acids. Twenty grams of the diketone, cooled to 0°, were mixed with 24 grams of potassium cyanide dis¬ solved in 30 c.c. of water, and, after standing for some time at room temperature, 3To c.c. of concentrated hydrochloric acid were added very slowly, the mixture being kept well cooled and shaken, and then left for forty-eight hours at room temperature. On -extraction with ether, this yielded 25 grams of viscous, yellow oil, which was at once mixed with twice its volume of concentrated hydrochloric acid, heated during 1 hour at 100°, and then steam- distilled. The dilactone came over slowly as a viscous, yellow oil, which sometimes crystallised at once in the condenser or the receiver and sometimes only after saturation of the aqueous dis¬ tillate with salt. After filtering off the separated dilactone, the remainder, mixed with some neutral products, was obtained by extracting the distillate with ether. The total yield of dilactone was about 5 per cent, of the weight of diketone taken; it melted at 74°, and the melting point was not changed by recrystallisation from ether (Found: C = 60-40; H = 7-39. Calc, for C10H14O4, C = 60-60; H = 7-07 per cent.). The mother-liquor left in the distillation flask, which was ap¬ parently not examined by Wallach, was allowed to cool, poured from the considerable quantity of tar formed, and thoroughly extracted with ether, when it yielded about 5 grams of crude crystalline acids, which on recrystallisation from boiling water were separated into the acid of m. p. 203—204° (4 grams), and the acid of m. p. 189° (1 gram), neither of which showed any depression in melting point when mixed with the acids of similar melting point prepared from a-terpinene. The crystalline dilactone, m. p. 74°, and the mixture of this with neutral products (see above) were separately treated with 2A-sodium hydroxide; the former dissolved completely, and on acidification the solution yielded an acid crystallising in rosettes of transparent