ON THE STUDY OF HYDRO-AROMATIC SUBSTANCES. 65 
readily explained, for the evolved hydrogen combines with some unaltered 
ester, and the result of the reaction is the production of methyl terephthalate 
and methyl hexahydroterephthalate. 
Al3. Dihydrobenzene. By Dr. A. W. Crosstey. 
In the last report of this Committee,! brief allusion was made to the 
preparation of A‘‘*-dihydrobenzene ; work in this direction has now been 
completed, with results which entirely confirm the preliminary experi- 
ments. The hydrocarbon obtained from dimethyldihydroresorcin by 
Crossley and Le Sueur”? was proved to be 1 : 1-dimethyl-\”** dihydro- 
CH CH 
Tae 
(CH,).CX pu 
GH, CH 
benzene, and by submitting dihydroresorcin to an identical series of 
reactions a hydrocarbon was obtained,’ which differed from any previously 
prepared dihydrobenzene in only combining with one molecule of bromine 
to give a dibromodihydrobenzene melting at 104°-5. It was therefore 
suggested that the double bonds would be in the position 1 : 3, and the 
hydrocarbon prepared by Baeyer ‘ and Markownikoff® would be A***-di- 
hydrobenzene, which is characterised by directly adding on four atoms of 
bromine to form a solid tetrabromide melting at 184°. Harries and 
Antoni ® consider that their work proves this suggestion to be incorrect. 
Unfortunately it was not found possible to prepare pure A‘: *-dihydro- 
benzene from dihydroresorcin, but this end has now been attained by the 
removal of the elements of hydrogen bromide from dibromotetrahydro- 
benzene.’ 
CH, . CHBr CH=CH 
CH. cue =2HBr+ CH, CH 
K ir r x > 
CH, . CH, CH, —CH 
; The reaction can only take place in one way, and therefore leaves no 
_ doubt as to the constitution of the resulting hydrocarbon, which like that 
obtained from dihydroresorcin only adds on two atoms of bromine to give 
a solid melting at 104°-5. That this latter substance is in reality a 
dibromodihydrobenzene is conclusively proved by the fact that on treatment 
with quinoline it Joses two molecules of hydrogen bromide, yielding 
benzene. 
It seems indisputable that, as already suggested, the hydrocarbon 
obtained from dihydroresorcin or from dibromotetrahydrobenzene is 
A***-dihydrobenzene, and the hydrocarbon giving the tetrabromide melting 
at 184° must therefore be A!‘ *-dihydrobenzene. 
' Southport, 1903, p. 182. 2 J. C. 8., 1902, 81, 822. 
® Crossley and Haas, J. C. S., 1903, 83, 494. + Annalen, 1894, 278, 88. 
5 Annalen, 1898, 302, 29. 6 Annalen, 1903, 328, 102. 
7 Proc. C.S., 1904, 20, 160. 
1904. r 
