222 KEPORTS OX THE STATE OF SCIENCE 



at the time,' but it was considered desirable to try to prepare the sub- 

 stance by another method, in the hope that a comparison of the two 

 specimens of the hydrocarbon would throw further light on the problem. 

 This has now been done, with the result that the correctness of the 

 earlier experiments and deductions are completely confirmed, allowing 

 the following conclusions to be arrived at : — 



1. The dimethyldihydrobenzene described by Crossley and Le Sueur 

 is 1 : 1 dimethyl- A-"*-dihydrobenzene, containing as impurity a very small 

 amount of some oxygenated substance, probably a methoxy- compound. 



2. The hydrocarbon described in this report (dimethyldihydro- 

 benzene C and R),'- and prepared by the elimination of two molecules 

 of hydrogen bromide from dibromodimethylhexahydrobenzene, is a mix- 

 ture, in approximately equal quantities, of pure 1 : 1 dimethyl- A'"*-di- 

 hydrobenzene and pure 1 : l-dimethyl-A-="'-dihydrobenzene. 



The starting-point in the synthesis was again dimethyldihydroresorcin 

 (Til), which was first converted into its ethyl ether (IV),-* and this by 

 reduction with sodium in absolute ethyl-alcoholic solution into 3-hydroxy- 

 5-ethoxy-l : 1-dimethylhexahydrobenzene (V) :■ — 



,CH.. COv .CH CO. 



CMe„< ' >CH CMe< ' Vh 



■\CH...C(OH)'^ \CH.,.C(OEt)'^ 



(111) (IV) 



/CH,-CH(OH). 



CMe/ ' \CHj. 



'^CHjCHCOEt)/ 



(V) 



The ethoxy- compound gives with fuming hydrobromic acid dibromo- 

 dimethylhexahydrobenzene (VI), which when treated with quinoline 

 loses readily and completely two molecules of hydrogen bromide, with 

 formation of dimethyldihydrobenzene, and this reaction takes place in 

 two ways, giving rise to 1 : l-diraethyl-A'^-*-dihydrobenzene (VII), or 

 to 1 : 1 dimethyl A-='-dihydrobenzene (v'lll) ; in approximately equal 



amounts. 



/CHj.CHBr. 



CMe < >CH2 



■\CHj.CHBr/ 



(VI) 



/ \ 



<^ \ 



/CH=:CHv /CH : CHv 



CMe/ >CH CMe/ >CH,. 



"\CH,.CH'^ '^CH : Cfl/ 



(VII) (VIII) 



• 5t'?-., 1903, 36, 2092. 



- To avoid confusion as far as possible, the hydrocarbon described in this 

 report, which is a mixture of pure 1 : 1 -dimetbyl-A^^^ dihydrobenzene and of 

 pure 1 : l-dimethyl-A2:>>-dihydrobenzHne, is referred to as dimethyldihydrobenzene 

 (C and R), the 1 : l-dimethyl-A'-=*-dihydrobenzene, prepared by Crossley and 

 Le Sueur, as dimethyldihydrobenzene (C and S), and the supposed 1 : 1-dimethyl- 

 A'^:5-dihydrobenzene of Harries and Antoni {loo. cit.) as dimethyldihydrobenzene 

 (H and A). 



» J.C.S., 1899, 75, 775. 



