VOL. 4 (1950) FREE RADICALS DERIVED FROM TOCOPHEROL I59 



which cannot be re-reduced directly to the original tocopherol because the phytol side- 

 ring is opened to make the quinone. When this quinone is reduced to its corresponding 

 hydroquinone, and this "tocopherylhydroquinone" is irradiated under proper condi- 

 tions, the absorption spectrum of the free radical is different from that produced by the 

 irradiated tocopherol itself. It resembles, with its yellow colour, more that of the 

 hydroquinone-methyl-ether. Hereby it is shown that the red radical produced from 

 tocopherol does not involve the opening of the phytol side-ring. The preserva.ion of the 

 free radical will also be aided by the fact that the opening of the phytol ring represents 

 a hydrolysis which cannot occur in the absence of water. There is, then, no reason, why 

 the univalent oxidation of tocopherol, especially in a non-aqueous solvent, should 

 not be reversible. 



SUMMARY 



Tocopherol, dissolved in a suitable mixture of organic solvents such as will, at the temperature 

 of liquid air, form a homogeneous glass, is irradiated with ultraviolet light. A red colour is developed 

 which disappears at slightly higher temperature. Similar observations are made with some other 

 substances related to hj'droquinones. The coloured substance is interpreted as a free semiquinone 

 radical. Its possible function for the vitamine and the antioxidant effect of tocopherol is discussed. 



RESUME 



Le tocopherol, dissous dans un melange approprie de solvants organiques, melange qui, a la 

 temperature de I'air liquide, forme un verre homogene, est irradie au moyen de lumiere ultraviolette. 

 Une coloration rouge apparait, qui redisparait lorsqu'on eleve quelque peu la temperature. Des 

 observations similaires ont ete faites avec quelques autres substances de nature hydroquinonique. 

 La substance coloree est consideree comme etant un radical semiquinonique libre. Son role possible 

 dans Taction vitaminique et antioxydante du tocopherol est discute. 



ZUSAMMENFASSUXG 



Tocopherol, gelost in einer geeigneten Mischung von organischen Losungsmitteln, welche bei 

 der Temperatur der fiiissigen Luft zu einem homogenen Glas erstarren, w-ird mit ultraviolettem Licht 

 bestrahlt. Es entsteht eine rote Farbung, welche bei hoherer Temperatur wieder verschwindet. 

 Ahnliches wird mit anderen Hydrochinon-ahnlichen Verbindungen beobachtet. Die gefarbte Sub- 

 stanz wird als ein Semichinon gedeutet und ihre mogliche Funktion bei der Rolle des Tocopherols 

 als Vitamin und als Antioxidant erortert. 



REFERENCES 



1 J. L. BoLL.\ND AND P. TEN Have, Traus. Faraday Soc, 43 (1947) 201. 



2 J. L. BoLLAND AND P. TEN Have, in The Labile Molecule, 'Discussions of the Faraday Soc.,'" 

 London 1947. 



3 G. N. Lew'is and D. Lipkin, /. Am. Chem. Soc, 64 (1942) 2801-8. 



* G. N. Lewis and Biegeleisen, /. Am. Chem. Soc, 65 (1944) 2424-6; 65 (1944) 2419. 



^ L. Michaelis, M. p. Schubert, and S. Granick, /. Am. Chem. Soc, 61 (1939) 1981-92. 



* S. Granick and L. Michaelis, /. Am. Chem. Soc, 62 (1940) 2241. 

 ' Walter John, Z. physiol. Chem., 250 (1937) 11; 257 (1939) 173. 



^ L. T. Smith, Chem. Revs, 27 (1940) 287-320 (Review of the chemistry of vitamin E). 



^ R. A. IVIorton, The Application of Absorption Spectra to the Study of Vitamins, Hormones and 



Coenzymes, 2dn Edition, Adam Hilger, Ltd., London 1942. 

 ^° Biological Antioxidants, Transactions of the first conference, Josiah Macy, Jr. Foundation, X.Y., 

 1946. Second Conference, 1947; third Conference (in press) 1948. 



Received February 14th, 1949' 



