THE ISOMERISM OF THE HYDROJUGLONS* 



EICHARD WILLSTAETTEE AND ALVIN S. WHEELER 



Thanks to the splendid researches of A. Bernthsen^ and F. 

 Mylius,^ the uncertainties of the constitution of jnglone have 

 been fully cleared up. The decomposition of juglone into /3- 

 hydroxyphthalic acid and its synthesis from 1, 5-dihydoxy- 

 naphthalene indicates that its structural formula is that of 8- 

 hydroxy-1, 4-naphthoquinone : 



OH O 



CO 



The study of the two hydrojuglones however remained in- 

 complete in certain important points, especially in regard to 

 their isomerism. 



Mylius isolated two isomeric compounds, a- and jS-hydro- 

 juglore, from green walnut shells. The first, which possesses 

 the higher melting point, is a true hydroquinone and oxidizes 

 easily to juglone. The ^-compound however does not pass di- 

 rectly into juglone. x\ccording to Mylius the two hydrojuglones 

 can be converted into each other in different ways. For ex- 

 ample, the a-form can be changed into the ^-form by distillation 

 or by the hydrolysis of its acetyl derivative. The /3-form may 

 be turned back into its isomer by heating a solution of it in 

 alcoholic dilute hydrochloric acid. Mylius explained the rela- 

 tions between the two isomers as positioai isomerism. He stated 

 that one of the para hydroxy] groups in the a-hydro juglone 

 changed its location in the nucleus of the disubstituted benzene 

 ring. This explantion was plausible for 'nearly thirty years 

 but the easy mutual transformations of the isomers are in our 

 view opposed to this theory. 



We find it is not necessary to distill the a-hydrojuglone in 



* Translated from Ber. der deutsch. chem. Gesell., 47,2796 (1914). 

 ^Ber. dpr deutsch. chem. Oesell., 17.194.5 (1S84); Bemthsen and Semper, 

 ibid. IS. 20". (1S.S.">) : 19,164 (1886), 20.9^4 (1887). 



^Ber. der deutsch. chem. Gesell.. 17.2411 (1884); 18,463,2567 (1885); also 

 Babilitationsschrift, Freiburg 1. B., 1885. 



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