The constitution of chrysophanic acid and of emodin / by H.A.D. Jowett, and C.E. Potter.

  • Jowett, H. A. D. (Hooper Albert Dickinson)
Date:
[1903.]
Catalogue details

Licence: In copyright

Credit: The constitution of chrysophanic acid and of emodin / by H.A.D. Jowett, and C.E. Potter. Source: Wellcome Collection.

    4/12 (page 1328)
    follows that both hydroxyls must be contiguous to a carbonyl group in the anthraquinone molecule. Furthermore, by fusion with caustic alkali or by oxidation with permanganate, it does not yield any derivative of benzoic acid, but gives rise only to simple oxidation products such as oxalic acid, from which it may be concluded that the hydroxyl groups are attached to one benzene residue and the methyl radicle to the other. If all three substituting groups were attached to one benzene residue or a hydroxyl to one and the methyl radicle and a hydroxyl to the other, fusion with caustic alkali would certainly furnish either benzoic acid or one of its derivatives (Liebermann, Ber., 1879, 12, 1293). Moreover, the methyl radicle attached to one benzene residue and the quinol group present in the other afford to oxidising agents two points of attack, and furnish an explanation of the ease with which disruption of the molecule occurs. The only possible formulae for chrysophanic acid are therefore OH \/-c°-V OH II. 5 :8-Dihydroxy-2-methylanthraquinone (formula II) has, however, been synthesised (Niementowski, Ber., 1900, 33, 1634), and appears to coincide in physical and chemical characters with chrysophanic acid. As it seemed likely that the possibility of the identity of the synthetical and natural products had been overlooked, we prepared some 5 :8-dihydroxy-2-metbylanthraquinone and found that it was not identical with chrysophanic acid. Formula II must therefore be abandoned, and we may regard I as the constitutional formula of chrysophanic acid, which is that previously suggested by Hesse (loc. cit.). If this formula for chrysophanic acid is accepted, it necessarily follows that chrysarobin and dichrysarobin must be represented as follows : [5 :8](0H)206H2<V^>C6H3-CH8[1], 'CH- (Chrysarobin.) !c6H2<^^)>C6H3-(jii3 (0H8)]206H2<®W>06H3-CJSC3. -0-i (Dichrysarobin.) We have endeavoured to synthesise 5 : 8-dihydroxy-l-methylanthra-- quinone by the condensation of hydroxysalicylic acid with o- and with m-toluic acids and of 1-methylphthalic anhydride with quinol, but in [5:8' (OH)