816 IX. THE VITAMIN E GROUP 



rotation. 5-Tocopherol has the highest specific rotation, while the lowest 

 value obtains with a-tocopherol. These data are summarized in Table 7. 



TABLE 6 

 Probable Absorption Maxima in the Infrared Spectrum of Some Tocopherols 



AND Their Derivatives" 



Hydroxy absorption Wave length 



(phenolic 



Wave length, C — O linkage). 

 Compound Type m M 



a-Tocopherol Phenolic 3.02 7.85 



7-Tocopherol Phenolic 3.02 8. 17 



5-Tocopherol Phenolic 3.01 8.28 



a-Tocopherol acetate — — 8. 18 



a-Tocopherol palmitate — — 8.06 



a-Tocopherol succinate Acid OH 3? 8. 16 



7-Tocopherol palmitate — — 8. 14 



a-Tocopherolhydroquinone triacetate. . — — 8.08 



2,5,6-Trimethylhydroquinone Phenolic 3.03 b 



a-Tocopherylquinone Alcoholic 2.93 — 



" Data adapted from H. Rosenkrantz, /. Biol. Chem., 173, 439-447 (1948). 

 '' Split band at 7.6 /x and another band at 8.23 m- It is uncertain which is due to 

 phenolic C — O linkage. 



TABLE 7 

 Specific Rotations of Tocopherols .\nd Esters in Ethyl Alcohol and Benzene' 



r ,25 Tube length, Soln. concn.. 



Tocopherol ^"^646.1 dm. g./lOO ml. 



Ethyl alcohol 



a- 0.32 1 14. 8 



y. 2.2 1 - 9.32 



/3- 2.9 1 7.15 



8- 3.4 1 15.48 



Benzene 



a- -3.0 1 13.50 



y- -2.4 1 8.59 



/3- 0.9 1 8.00 



8- 1.1 1 10.86 



" M. H. Stern, C. D. Robeson, L. Weisler, and J. G. Baxter, /. Am. Chem. Soc, 69 

 869-874(1947), p. 872. 



One of the most important uses of the tocopherols in commerce results 

 from their ready susceptibility to oxidation. They are thus able to pro- 

 tect other less vulnerable compounds from destruction by breaking up the 

 chain of oxidation reactions. Such antioxidant activity continues until 

 all of the tocopherol has been exhausted. 5-Tocopherol is the best anti- 

 oxidant of the group, followed in order by the 7-, /S-, and a-isomers. This 

 has been demonstrated by in vitro tests on the protective action upon 



