Action of Beckmann's chromic acid mixture on some monocyclic terpenes / by T.A. Henry and H. Paget.

  • Henry, Thomas Anderson, 1873-1958
Date:
[1928.]
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Licence: Public Domain Mark

Credit: Action of Beckmann's chromic acid mixture on some monocyclic terpenes / by T.A. Henry and H. Paget. Source: Wellcome Collection.

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    which was redissolved in sufficient ether and separated into acid (B) and neutral (A) portions by repeated agitation with a saturated aqueous solution of sodium carbonate. A further quantity of acid (C) was usually obtained by concentrating the chromic acid liquor after neutralisation, again making it acid and extracting it with ether. Limonene. Limonene is much less readily attacked by Beckmann’s mixture than phellandrene, but oxidation proceeds a little more rapidly if the terpene is diluted with an equal volume of glacial acetic acid. Limonene (d\f. 0*8484, [a]]f -f- 90-1°) (50 c.c.), dissolved in glacial acetic acid (50 c.c.), was shaken mechanically for 5 days- with 1000 c.c. of Beckmann’s mixture. The unattacked terpene was then separated (46 c.c.) and the products were treated as described above; after 14 repetitions of the process, 8 c.c. of oil remained, [a]}f + 48*5°. The neutral extract (A) (28 g.), after distillation, yielded a semicarbazone which crystallised from alcohol in minute needles, m. p. 210°, [a]]f -f- 1*28° in acetic acid (c = 1*486) (Found: C, 54*4; H, 8*0; N, 18*1. C11H1903N3 requires C, 54*8; H, 7*9; N, 17*4%). This was proved by a mixed melting- point determination to be identical with the semicarbazone of the keto-lactone, C10H16O3, obtained by the oxidation of a-terpineoL The keto-lactone, recovered as described (p. 76), had m. p. 58—60°; [«]})* — 2*12° in water (c = 1*552) and — 7*87° in benzene (c = 2*008) (Found : 1 g. equiv. to 5*31 c.c. of A-sodium hydroxide. Calc, for C10H16O3, 5*4 c.c.). The residue from the distillation of the crude extract deposited on standing a small amount of a neutral crystalline substance, insoluble in ether, with which it was well washed; it then melted at 121°, alone or mixed with a specimen of 1:2: 8-trihydroxy- terpan, C10H20O3, prepared from a-terpineol by oxidation with potassium permanganate as described by Wallach (Annalen, 1893, 275, 153). a-Phellandrene. The four supplies of commercial a-phellandrene used had the following constants: dg 0*8525, [a]g* - 98*5°; dg 0*8519, Mb’ 67*7°; dg 0-8828, [a]1/— 56-1°; dg 0*8531, [a]f-75*0°. From 1 litre of terpene the average yields of the four crude oxidation products referred to above were (A) 110 e * (B) 102 e (C) 28 g.; (D) 590 g. ” Extract A (Neutral Oil).—This on treatment with semicarbazide acetate in alcohol yielded immediately a semicarbazone, crystallising in colourless, glistening leaflets, but all attempts to isolate the