RELATIONSHIPS BETWEEN COLOUR AND CONSTITUTION 



55 



/9-Carotene mono-epoxide, 10 conjugated double bonds and 1 epoxide group, longest 

 wavelength maximum in CSg at 511 m/x. 



Conversion, of a mono-epoxide to a di-epoxide results in a further displace- 

 ment of the absorption maxima by 6-9 mij, towards shorter wavelengths. 



4. Conversion of a carotenoid mono-epoxide to the isomeric furanoid oxide 

 results in a displacement of the absorption maxima towards the blue end of 

 the spectrum. For the longest wavelength bands this displacement amounts 

 to 19-22 niju. 



Examples: 



^-Carotene mono-epoxide 



Mutatochrome 



a-Carotene mono-epoxide 



Flavochrome 



Capsanthin mono-epoxide 

 Capsochrome 



longest wavelength maximum in CSj at 511 m//. 

 longest wavelength maximum in CSg at 489 m/i. 

 longest wavelength maximum in CSg at 503 m^. 

 longest wavelength maximum in CSj at 482 m/n. 

 longest wavelength maximum in CSg at 534 mfi. 

 longest wavelength maximum in CSj at 515 m^. 



Conversion of a di-epoxide into the di-furanoid isomer results in a hypso- 

 chromic displacement approximately twice as great, i.e. ca 40 mfz. 



5. Some carotenoids have a completely (e.g. lycopene) or partly (e.g. 

 y-carotene) open-chain structure. If such an open chain undergoes one ring- 

 closure, the absorption maxima are displaced by 4-5 m^ towards the blue end 

 of the spectrum. If both ends of the chain undergo ring closure, the longest 

 wavelength maximum is displaced by ca. 10 m/^. 



Examples: 



y-Carotene contains 11 conjugated and 1 isolated double bond. Taking ^-carotene 

 (11 conjugated double bonds), longest wavelength maximum in CSg at 520 m/j., 

 as a basis, the position of the longest wavelength absorption maximum of 

 y-carotene is calculated to be 529-530 m/i. The observed longest wavelength 

 maximum of y-carotene is at 533.5 mfi. 



Lycopene, contains 11 conjugated and 2 isolated double bonds. Taking /5-carotene 

 as a basis, the position of the longest wavelength maximum is calculated to be at 

 538-540 m/.i. The observed longest wavelength maximum of lycopene lies at 

 548 m/t. 



6. Introduction of a hydroxyl group only results in a small hypsochromic 

 displacement (1-2 m/^). 



Examples: 



/3-Carotene longest wavelength maximum in CSj at 520 m/i. 



a-Carotene longest wavelength maximum in CSj at 509 m/x. 



Lycopene longest wavelength maximum in CSj at 548 mfi. 



Zeaxanthin(Dihydroxy-/3-carotene)longest wavelength maximum in CS2 at 517 m/j.. 

 Xanthophyll (Dihydroxy-a-carotene) 



longest wavelength maximum in CSg at 508 m/n. 

 Lycophyll (Dihydroxy-lycopene) longest wavelength maximum in CSg at 546 rxifi. 

 References p. 5g. 



