CONTENTS XVll 



V. Chemistry of the Phosphatides and Cerebrosides (continued) 



(a) Structure 496 



(b) Properties 496 



d. Hydroxynervonic Acid 497 



(a) Structure 497 



(b) Properties 497 



e. n-Hexacosenic Acid 497 



f . Methods for Separation of the Acids 497 



(a) Separation of the Saturated Fatty Acids 498 



a'. Thierfelder Procedure 498 



b'. Thierfelder-Klenk Procedure 498 



(b) Separation of the Unsaturated Acids 498 



(c) Calculation of Amount of Each Fatty Acid 499 



(5) Carbohydrate Component 499 



8 . Methods for Determination of the Cerebrosides 501 



9 . Compounds Related to the Cerebrosides 502 



(1) Gangliosides 502 



a. Neuraminic Acid 504 



(2) Cerebrosides Containing Two Sugar Molecules 504 



VI. Carotenoids and Related Compounds 507 



A. General Considerations on the Relationship between Carotenes and the 



Vitamins A 507 



B. The Carotenoids 510 



1 . Introduction , . . . . 510 



2 . Structure and Occurrence of Hydrocarbon Carotenoids of the C40 



Series 513 



(1) 0-Carotene 514 



a. Structure 514 



b. Occurrence 517 



c. Related Compounds 525 



(a) /3-Carotene Oxide 525 



(b) /3-Carotene Mono-epoxide 526 



(c) j8-Carotene Di-epoxide 526 



(d) Luteochrome 527 



(e) Ox}'-/3-carotene 527 



(f ) Semi-/3-carotenone 528 



(g) Oxy-semi-/3-carotenone 528 



(h) Anhydro-semi-/3-carotenone 529 



(i) /3-Carotenone 529 



(j) Bis-anhydro-(8-carotenone 529 



(k) Bis-anhydro-dihydro-/3-carotenone 530 



(1) Dihydro-/3-carotenone 530 



(m) /3-Carotenone Aldehyde 531 



(n) /3-Apo-2-carotenal 531 



(o) /3-Apo-2-carotenol 531 



(p) /3-Apo-4-carotenal 532 



(q) /3-Apo-4-carotenol 532 



(r) Dihydrocarotenes 532 



d. Properties 533 



(2) «-Carotenc 533 



