PROPERTIES OF THE K VITAMINS 



841 



ring closure occurs on treatment of the chloride with aluminum chloride, 

 with the resultant formation of 2-methyl-a:-tetralone. The latter product 

 yields 2-methyl-l,2,3,4-tetrahydronaphthalene on reduction; this can be 

 dehydrogenated to 2-methylnaphtlialene on treatment with sulfur or 

 selenium; this product is readily oxidized to the quinone. 



5. Properties of the K Vitamins 



In common with other fat-soluble vitamins, the natural members of the 

 vitamin K group dissolve only in fat solvents, and are insoluble in aqueous 



240 



260 280 300 



WAVE LENGTH, mjU. 



320 



340 



360 



Fig. 2. Absorption curves of 1,4-naphthoquinone (I) and of the diacetate of 

 naphthoquinone (II) in hexane.^* 



media. They are especially soluble in petroleum ether, diethyl ether, 

 hexane, acetone, and chloroform, but only sparingly soluble in methyl al- 

 cohol. The synthetic members of the group which no longer have the long 

 aliphatic hydrocarbon chain attached to the naphthoquinone nucleus are 



