ON HYDRO-AROMATIC COMPOUNDS WITH SINGLE NUCLEUS. 127 



Towards hydroxylamine, phenylhydrazine, and hydrocyanic acid 

 dihydroresorcin behaves as a diketone, formula ( i.) above, giving in the 

 latter case the nitrile of dihydroxyhexahydroisophthalic acid 



,CH, . COH . COOH 

 CEI„ NcHo 



\CH„ . COH . COOH 



"When heated with barium hydroxide the ring is broken, and c-ketohexoic 

 acid produced ' 



.CH, . CO XHj . CO 



CH, /CH CHj ^CHj 



"^CH, . COH ^CHj . COOH 



Substituted dihydroresorcins may be obtained by various methods,^ of 

 which the two following may be taken as typical : — 



(i.) The condensation of ethyl malonate with a^-unsaturated ketones.^ 



(CH,), (CH3), (CH3), 



CH + CH/COOCoHs), = CH, CH . COOC^H. = C,H.OH + CH, CH.C00C,H5 



I ■ I ' I I ' I 



CO CO COOC^Hj CO CO 



\ \ \/ 



CH3 OH3 CHj 



Substituted malonic acids may also be employed.* 



(ii.) The condensation of ethyl aceto-acetate and ethyl crotonate.' 



CHj CHg CH. 



CH CH CH 



COOCoHj . CH, + CH = COOC2H3 . CH CH, = COOC3H5 . CH CH^ + C„H,OH 



The ethyl dihydroresorcylates produced by either of the above methods 

 on hydrolysis give free acids, which immediately lose carbon dioxide, 

 forming dihydroresorcins. 



.CHCCOjCjHJCO ,CH, . CO 



(CH,),.C \cHj (CH3),.C \CH 



XCH., CO "^CH, .COH 



The properties of substituted dihydroresorcins are identical with those 

 of the initial member of the series. The above-mentioned behaviour with 



' Vorlander, Annalen, 1897, 294, 272. 



- Ber., 1894, 27, 2053, 2126, 2338. 



' Vorlander, mpra, p. 253 ; Crossley, J.G.8., 1899, 76, 771 ; 1902, 81, G75. 



< Crossley, J.C.S., 1901, 79, 138. 



' Vorlander, Annalen, 1899, 308, 184, 



