ON THE STL'DY OF IIYDKO-AROMATIC SI'IISTANCES. 220 



these compounds is somewhat striking. Thus, while dimethyldihydro- 

 resorcin 



I I 

 OC CO 



\/ 



€H., 

 is colourless, isonitrosodimethyldihydroresorcin 



I I 

 OC CO 



\/ 



C : N.OH 

 is yellow ; its potassium and ferrous salts are deep blue, and its ammo- 

 nium salt violet : the monoxime 



1 I 

 OC C : N.OH 



C : N.OH 

 is colourless, but dissolves in alkalis to a yellow solution, and gives with 

 ferrous sulphate a deep azure blue. The dio.xime 



1 I 

 HO.N : C C : N.OH 



U : N.OH 



on the other hand, is greyish pink, but gives a yellow solutioii in caustic 

 alkalis, and produces with ferrous sulphate a violet colour. Replace- 

 ment of one of the carbonyl oxygen atoms in isonitrosodimethyldihydro- 

 resorcin by the imino group 



II 

 OC C : NH 



\/ 



C ; N.OH 



changes the colour from yellow to deep violet ; tlie potassium salt of 

 this compound is magenta, while the ferrous salt is deep blue. 



Acids. — A number of carboxylic acids of the hydroaromatic serie.s 

 have been synthesised by Wallach ' by condensing cyclic ketones with 

 ethyl bromoacetate. The hydroxyl group in the resulting esters is 

 replaced by bromine through the agency of hydrogen bromide, and the 

 halogen free acids obtained by treatment with zinc and acetic acid. 





\<i Y^^"^ Y-^' \<i.CH.,COOH 



CH.COOH ^CH.,.COOH 



Skita- concludes from a study of ethyl 4-amino-2 : 6 : 6-trimethyl- 

 hexahydrobenzene - 1 - carboxylate, prepared from ethyl isophorone- 

 carboxylate, that hydroaromatic amino- acids show cis-<?'a?2s-isomerism ; 

 that they are similar in their chemical behaviour to the aliphatic amino- 

 acids, and also physiologically, in that they possess the property of pro- 

 ducing local anaesthesia. 



Amines. — Gutt^ has prepared hexahydrobenzylamine and the five 



' Cent. Blatt., 1907, ii. 52. • Ber. 1907, 40, 4167. ' Ibid., 1907, 40, 2061. 



