190 Journal of the Mitchell Society [March 



PKEPAKATION OF JUGLONE 



We fonnd that the oxidation of 1, 5-dihydroxyiiaphthalene 

 according to Bernthsen and Semper^ was the best method for 

 the preparation of juglone although we were unable to secure a 

 higher yield of the pure quinone than sixteen per cent. 1, 5- 

 Dihydroxynaphthalene was purified by dissolving in ether and 

 reprecipitating in petroleum ether. It forms colorless prisms 

 which melt at 254°. 50g 1, 5-Dihydroxynaphthalene, after 

 rubbing up with a small quantity of water, are introduced in 

 small portions into a chromic acid mixture consisting of 240g 

 sodium bichromate, 340g concentrated sulfuric acid and 3400cc 

 water. The temperature is not allowed to rise above 10°. On 

 the following day the brovimish yellow precipitate is filtered off, 

 dried and boiled up with ligroin, 70-80°. The impurities re- 

 main undissolved and the extracts upon concentration yield 

 8.8g juglone in the form of deep yellow needles. They show a 

 melting point of 149-50°, when the substance is introduced into 

 a bath previously warmed to 140°. 



We found that juglone could also be obtained from 1, 5- 

 dihydroxynaphthalene by oxidation with lead peroxide. The 

 yield is somewhat higher but the process is not practical. It is 

 noteworthy how much the yield here depends upon the quantity 

 of the solvent and of the oxidant on the surface of which the 

 oxidation takes place. lOOg Lead peroxide in one liter of ben- 

 zene yields the same qua.ntity of juglone whether 5g or 0.5 

 g dihydroxynaphthalene are used. 0.5g 1, 5-Dihydroxynaph- 

 thalene are boiled five hours in one liter of benzene with lOOg 

 good lead peroxide. The beautiful yellow solution is concentra- 

 ted in vacuum to lOcc and mixed with petroleum ether. 0.1 5g 

 Juglone crystallizes out in pure yellow needles. 



0.1252g Substance gave 0.3143gCOo; 0.0402g TL^O 

 Calculated for CioHgOs: 0,68.95; H, 3.47 

 Found 0, 68.46; H, 3.59 



1, 8-Dihydroxynaphthalene does not yield juglone on oxida- 



"Ber. der deutsch. chem. GeseU., 20,938 (1887). 



