126 REPORT — 1902. 



and (iii.) by the action of zinc and acetic acid on nitrohexahydrobenzene. ' 

 It is a liquid with an odour of peppermint, and is readily oxidised by nitric 

 acid to adipic acid. Homologues have been prepared by method (ii.) from 

 substituted pimelic acids. ^ 



Of the three possible isomeric diketones two, viz., the 1 : 3- and 1 : 4- 

 compounds are known. 



Dihydroresorcin (1 : 3-diketohexahydrobenzene) was first prepared by 

 Merling ^ by the reduction of resorcinol with sodium amalgam ; it can 

 also be obtained by the action of sodium ethylate on ethyl <3-ketohexoate.'* 



Dihydroresorcin reacts in some cases as a diketone, but its most usual 

 form is that of a ketone alcohol. 



.CH„ . CO .CH„ . CO 



CH„ (1.) \CH„ CH„ (ii.) ^CH 



^CH, . CO \CH„ . C . OH 



It is a crystalline substance which dissolves in water with an intense 

 acid reaction ; the solution gives a violet colour with ferric chloride, 

 decomposes the carbonates of the alkali metals and silver in the cold, with 

 the formation of salts, formula (ii.). It is readily oxidised by potassium 

 permanganate, yielding glutaric acid, thus showing that it could not have 

 the constitution represented by the formula 



^CH, . CO 



CH., \CH„ 



\CH=COH 



Alkyl iodides react with the silver salt, forming ethers 



,CH„ . CO 

 CH, \CH 

 \cHj-COCoH5 



and not 



.CH„ . CO 

 CH. "^CHCjHj 



^CH, . CO 



because they are easily hydrolysed with regeneration of dihydroresorcin. 

 With acetyl chloride only a mono-acetylated product is obtained ; and 

 with halogen acids or bromine additive products. The dibromide formed 

 in the latter case readily loses the elements of hydrogen bromide, giving 

 monobromodihydroresorcin, having the formula 



CH; . CO 



CH, \cBr 



\CH., . C . OH 



because it decomposes the carbonates of the alkali metals, gives a violet 

 colour with ferric chloride, and nascent hydrogen regenerates dihydro- 

 resorcin.'^ 



> Annalen, 1 898, 302, in. 



= Zelinsky, Ber., 189.5, 28, 781, 1313, 2914 ; and 1896, 29, 214, 731. 



3 AnnaJen, 1894, 278, 20. * Voilancler, Annalen, 1897, 294, 253. 



5 Compare Vorliiader, Amiakn. 1902, 382, 251. 



