180 REPORT— 1903. 



dihydrobenzenes and dihydrobenzenecarboxylic acids,' as illustrated by 

 the following example : — 



CH, .C CO CH3.C! C\^„ 



■ I I I I " I "" 



H,C CH, . H.C CHj 



CH„ CH„ 



CH CH 



^\ //\ 



CH3 .0 C . CH., .CCCjHj C fla . C C . CH3 



I III II ' ■ I IV II 



H,0 CH H„C CH 



\/ '\/ 



CHj CH2 



Methylketotetrahydrobenzene (i) when treated with zinc and ethyl- 

 oromacetate gives rise to an oxy-ester (11), which cannot be isolated, as it 

 so readily loses water, giving an unsaturated ester (in). This latter, on 

 saponification, yields the corresponding dihydro-meta-tolylacetic acid, 

 which when heated under pressure evolves carbon dioxide, with produc- 

 tion of dihydro-meta-xylene (iv). 



Hydroxy- derivatives. — 1 : 2-dihydroxyhexahydrobenzene.^ Metliyl- 

 cyclohexanose.^ 



Dihydroresorcins. — Tlie action of phosphorus haloids on dihydroresor- 

 cins ■* confirms the opinion that these substances behave in general as if 

 they possessed the ketoenol (i), and not the diketonic structure (11). 

 /CH,, . CO .CH, . CO .CH., . CO 



CMe., I "^CH CMe, 11 \cH„ CMe., in \cH 



\CH., . COH ^CHo. CO \CH.,.CCI 



Thus dimethyldihydroresorcin gives with phosphorus trichloride, 5-cliloro- 

 3-keto-l : l-dimethyl-A'*-tetrahydrobenzene (m), and with phosphorus 

 tribromide the corresponding bromo- derivative ; whereas phosphorus 

 pentachloride produces 3 : 5-dichloro-l : 1 -dimethyl- A'^ -^-dihydrobenzene 



.CH3 = CC1 



CMe^ I J>CR 



\CH„ — CCl 



Phosphorus pentabromide behaves as a mixture of bromine and phos- 

 phorus tribromide, and gives rise to a complicated mixture of bodies, 

 varying greatly according to the conditions of experiment. Among the 

 substances isolated were bromodimethyldihydroresorcin, tribromoketo- 

 dimethyltetrahydrobenzene, and several bromoxyleuols, which latter are, 

 however, not primary products of the reaction. 



Acids. — A method for the synthetical production of dihydrobenzene- 

 carboxylic acids, with ketotetrahydrobenzenes as starting-point, has 

 already been alluded to. Hexahydro-aromatic acids and polyraethylene- 

 carboxylic acids in general can be prepared '^ from the iodine or bromine 



' Wallach, Annalen, 1902, 323, 135. = Brunei, Compt. Rend., 1903, 136, 383. 



=• Zelinsky and Roschdestwensky, Bar., 1902, 35, 2695. 



* Crossley and Le Sueur, J.C.S., 1903, 83, 110 ; Crossley and Haas, ibid. 494, 

 » Zelinsky, Ber., 1902, 35, 2687. 



