I BIXIN 265 



Solvent Absorption maxima 



Carbon disulphide 527 491 458 rtijU 



Chloroform 503 469.5 440 m/i 



Dihydronorbixin C24H30O4 : 



Karrer and co-workers prepared dihydronorbixin by boiling labile norbixin 

 dissolved in 2.1 mols of dilute sodium hydroxide with excess ammonia and 

 2.3molsof titanium trichloride*^. Dihydronorbixin crystallises from ether in 

 yellow clusters, which sinter at 197°. It readily dissolves in acetic acid, acetone 

 and chloroform, but is only sparingly soluble in ether and almost insoluble in 

 ligroin. It is readily oxidised in air. 



The large displacement (about 70 m/j,) of the absorption maxima on passing 

 from norbixin to dihydronorbixin indicates that the two carboxyl groups are 

 no longer conjugated with the system of conjugated double bonds and that the 

 addition of hydrogen takes place at the i : 18 positions. 



I I I 1 



HOOC-CH2CH=C-CH=CHCH=G-CH=CHCH=CH-C=CHCH=CH-C=CH-CH2-COOH 



Dihydronorbixin 



Solvent Absorption tnaxima 



Carbon disulphide 454 428 m// 



Chloroform 435 410 m/u. 



Perhydronorbixin C24H4g04 (3:7:12:16-tetramethyloctadecane-l :18-dicarboxy- 

 lic acid) : 



This compound was obtained by Herzig and Faltis*^ by boiling perhydro- 

 methylbixin with potassium hydroxide. The total synthesis was achieved by 

 Karrer and Benz** by the method described above (p. 258). Perhydro- 

 norbixin is a viscous, colourless oil. B.p. 25o°/o.3 mm., 245.5°/o.24 mm., 

 227°/o.03 mm.*5. D^° 0.953; n^ 1.468*5 i|- ^g insoluble in water. By esterification 

 with diazomethane, or with a mixture of methanol and hydrogen chloride, 

 Herzig and Faltis*^ obtained perhydromethyibixin. 



a:a'-Dihydroxyperhydronorbixin dimethyl ester CjeHj^Og (I) : 



CHo Gilo 



(I) 



HjCOOC- CH(OH)- CHa- CH- CHa- CHj- CHj- CH- CHaCH^ 



Karrer and co-workers*' converted perhydronorbixin into a : a'-dihydroxy- 

 perhydronorbixin dimethyl ester (I) by the action of bromine and red phosphorus 

 followed by potassium hydroxide and diazomethane. The ester is obtained as 

 an almost colourless oil, b.p. 2i3-2i6°/o.i4 mm. 

 References p. 2go-2g4. 



