ON THE STUDY OF HYDRO-AROMATIC SUBSTANCES. 109 
It follows from the above evidence that the supposed 3 : 4-dibromo- 
1 : 1-dimethyl-hexahydrobenzene ! is a mixture of this substance with the 
corresponding 2 : 3-dibromo-derivative. When treated with quinoline 
the former (X VIII.) loses the elements of hydrogen bromide to give 
1 : 1-dimethyl-A?*!-dihydrobenzene, which forms the main portion of the 
resulting mixture of hydrocarbons. But in the case of 2 : 3-dibromo- 
CH,. CHBr OH : CH 
oMexe “OHBr  -¥ CMe, cu. 
CH,—CH, ” cH, .cH7 
XVII, 
hte 1-dimethyl-hexahydrobenzene (XIX.) the removal of the hydrogen bro- 
mide cannot take place in an exactly similar manner, because the carbon 
CHBr.CHBr Crate 
cme SCH.» 2... OMe CH 
Oe ee i SN On CRO.” 
atom to which the gem-dimethy] group is attached has no hydrogen atoms in 
connection with it. The reaction might take place, giving rise to a sub- 
stance of formula XX. containing a treble bond, or the two bromine atoms 
might be alone removed, possibly as a quinoline bromide. The former sug- 
gestion does not seem probable, because, although the hydrocarbon would 
give aa-dimethyladipic acid on oxidation, it would he isomeric with di- 
methyldihydrobenzene, but analysis showed the substance to be a mixture 
of dimethyldihydro- and dimethyltetrahydro-benzenes. In the latter case 
1 : 1-dimethyl-A?-tetrahydrobenzene would result, which would also give 
aa-dimethyladipic acid on oxidation, and, furthermore, its presence would 
be in agreement with the analytical data. 
Recent Work on Hydro-aromatic Substances. 
By Professor A. W. Crosstey. 
Hydrocarbons.—The ozonides of hydro-aromatic hydrocarbons ? pro- 
duced by the direct addition of ozone to a double bond in a six carbon 
ring, differ markedly from analogous derivatives obtained from open chain 
hydrocarbons, or from members of the aromatic series, in being very 
stable towards water. Thus the ozonide of 1 : 1 : 3-trimethyl-A?-tetra- 
hydrobenzene (cyclogeraniolene) is with difficulty acted on by water ; 
the ozonide of tetrahydrobenzene is slowly changed by boiling with water, 
yielding principally adipic acid and small quantities of adipic aldehyde, 
whereas the ozonide of dihydroxylene does not give any definite products. 
Furthermore, the ozonides of hydro-aromatic hydrocarbons show irregulari- 
ties in their composition, for though tetrahydrobenzene ozonide has the 
normal composition O,H,,)Q3, the derivative obtained from 1 : 1 : 3-tri- 
methyl-A?-tetrahydrobenzene appears to contain four atoms of oxygen 
_and to possess a double molecular weight. This alone would not preclude 
the use of such substances for the determination of the constitution of 
’! Crossley and Renouf, J.C.S., 1905, 87, 1501. 
2 Harries and Neresheimer, Ber., 1906, 39, 2846, 
