The constitution of umbellulone. Pt. III / by Frank Tutin.

  • Tutin, Frank.
Date:
1908
Catalogue details

Licence: Attribution 4.0 International (CC BY 4.0)

Credit: The constitution of umbellulone. Pt. III / by Frank Tutin. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    in the original communication, it now appears necessary that these should he considered. If umbellularic acid does not contain a five- membered ring, it must be represented by the following formula : pJ53>CH-C(C0aH)-CH-C02H C 3 \ / ch2 It is well known, however, that the cyclopropane ring is, in general, somewhat unstable. A. Kotz has pointed out (/. pr. Chem., 1903, [ii], 68, 174) the generalisation that simultaneous substitution by a carboxyl group and an alkyl or phenyl radicle decreases the stability of the cyclopropane ring, and, furthermore, that in the pi’esence of an alkyl or phenyl group the instability increases with the number of carboxyl groups. With consideration of these conclusions, 0. Aschan (Chemie d. AlicycUschen Verb., 1905, p. 244) adds that, in general, the occurrence of a quaternary carbon atom appears to increase the readiness with which the cyclopropane ring is opened. According to these generalisations, the isopropylcyc^opropanedicarboxylic acid repre- sented above should be a compound in which the ring is readily ruptured, for it contains a cyclopropane ring substituted with an alkyl radicle and two carboxyl groups, and, moreover, it also contains a quaternary carbon atom. Umbellularic acid, however, is an extremely stable substance. It is unaltered by heating with concentrated hydrochloric acid for five hours at 190°, and hydrobromic acid also has no action on it. It is not appreciably oxidised by alkaline potassium permanganate at 60°, and was recovered unchanged after boiling for ten hours with eight times its weight of a mixture of three parts of fuming nitric acid and one part of water. When heated for two hours on the water-bath with bromine and red phosphorus, it was also recovered unchanged, and after boiling for five hours with undiluted fuming nitric acid, besides unchanged umbellularic acid, only a trace of oxalic acid was obtained. In addition to considerations concerning the stability of the ring, it would not be expected that a compound containing an isopropyl group would exhibit such great stability towards nitric acid, as y>-cymene, for example, when treated with this acid in the cold, gives /j-tolyl methyl ketone, together with other compounds, and when warmed with nitric acid yields yj-toluic acid. isoPropylsuccinic acid, also, is fairly readily attacked when heated with fuming nitric acid. The properties of umbellularic acid therefore certainly seem to indi- cate that it does not possess the cyclopropane structure. Semmler, in his recent publication (loc. cit.), states in the first place that the physical properties of umbellulone are not in agreement