132 VITAMIN D GROUP 



I. Nomenclature and Formulas 



ROBERT S. HARRIS 



Accepted names: Vitamin D2 (or calciferol) from ergosterol by irradia- 

 tion; ergocalciferol 

 Vitamin D3 (or activated 7-dehydroch.olesterol) from 7- 

 dehydrocholesterol by irradiation; cholecalciferol 

 Obsolete names: Rachitamin 

 Rachitasterol 

 Antirachitic vitamin 

 Empirical formulas: Vitamin D2: C28H44O 

 Vitamin D3: C27H44O 

 Chemical names: Vitamin D2 



Vitamin D3 



Structure: 



H. CH3 



H 

 Vitamin Da 



n. Chemistry 



CHARLES E. BILLS 



The term vitamin D is applied to several antiricketic' substances derived 

 from, or associated with, the sterols. The existence of the vitamin was first 



^ The English word rickets, which probabI.y derives from wr,vgates (crooked goings), 



