DEFINITIONS AND NOMENCLATURE 



CH3 CHj CH^ CHj 



I C ^C I' 



/ \6 7 8 9 10 II 12 13 14 15 15*14' 13' 12' 11' 10' 9' 8' 7' 6' \ 



2 CHi c — C = C-C = C-C = C— C = C— C = C— C = C — C=C— C=C-C=C-C CHzZ' 



I II /i /< c'Hj /< A |!< CH, H H H H CH3 H H H CHj H H || j 



3 CHj C-CHj CHj— C CH, 3' 



CH2 y-carotene CH, 



4 4' 



similarly an a-ionone-containing moiety would take preference over 

 the open chain ( ^p-ionone) moiety, although a naturally occurring com- 

 pound containing such a combination has not yet been noted. 



In the case of carotenoids in which the ionone ring is not opened at 

 position 1 but at some other point, the Commission has made no recom- 

 mendation, but Professor Karrer has informed the author that the 

 numbering should remain the same. This point arises in the case of 

 capsanthin. 



CH, ^CH3 CH, CHj 



rc ^CY 



_/ \6 7 8 9 10 II 12 15 14 15 15' 14' ,15' 12' II' 10' 9' 8' 7' 6'/ \ 

 2 CH; C-C = C-C = C-C=C-C=C-C=C— C = C-C = C— C=C-C=C-C CHj 2 



un \ II IH H CH3 H H H cl^3 H H H H CH3 H H ^ ci^3H H I OH 



"j^C .C-CH3 CH2 C( 3' 



" CHz _ ., CHjS^Hf 



4 Capsanthin 4, 



The carotenoid hydrocarbons are designated by the term carotenes ; 

 carotenoids containing oxygen are to be regarded as derivatives of 

 carotenes, and thus carotenoid alcohols, ketones, aldehydes and acids 

 are characterized by the suffixes '* ol," " one," *' al," *' oic," or by the 

 prefixes " hydroxy," " keto," " aldo," " carboxy." The modification 

 of the ending '* xanthin " to ** xanthol," ** xanthone," etc., to indicate 

 the function of the oxygen atom(s) is not permissible ; e.g.y Crypto- 

 xanthin or 3-hydroxy-[3-carotene but not Cryptoxanthol. Karrer has 

 recently observed the natural occurrence of carotenoid epoxides and 

 oxides containing a furan ring (see p. 47) ; these are termed respec- 

 tively 5 : 6-epoxy carotenoids, and 5 : 8-epoxycarotenoids, e.g.^ 



Z' \6 7 8 9 ^ /^ \6 7 



2CH, C-C = C-C^ aCH^ C=-CH 



CHz CM, ^^2 CH3 ■» 



4 4 



A 5 : 6-epoxycarotenoid A 5 : 8-epoxycarotenold 



