ON THE STUDY OF HYDRO-AROMATIC SUBSTANCES. 61 
side-chains (ethyl, propyl, &c.) part of the latter is split off. For example, 
‘ethylbenzene gives principally ethylhexahydrobenzene, but also small 
amounts of methylhexahydrobenzene. Sabatier and Mailhe! have further 
investigated the product obtained by passing benzene and hydrogen over 
reduced nickel, and find that if the temperature be maintained at 250° 
pure hexahydrobenzene is formed, identical in all respects with that 
occurring in Caucasian petroleum. If hexahydrobenzene be passed over 
reduced nickel at 270° to 280°, it is decomposed into benzene and hydrogen, 
which latter reacts with the benzene, forming methane. An energetic 
substitution reaction takes place when chlorine acts on hexahydrobenzene 
at a temperature of 0°, resulting in the formation of a mixture of mono-, 
di-, tri-, tetra-, and hexa-chloro- derivatives.” 
According to Markownikoff,? methylhexahydrobenzene has not been 
obtained pure by the methods so far described ; for example, when isolated 
from Caucasian petroleum, it is contaminated with normal heptane. It 
can, however, be prepared in the pure condition by the action of zinc dust 
on an aqueous alcoholic solution of 3-bromo-1-methylhexahydrobenzene. 
The hydrocarbon obtained by eliminating the elements of hydrogen bro- 
mide from this latter substance ‘ is a mixture of the two methyltetrahydro- 
benzenes with the double bonds in the 2 : 3 and 3 : 4 positions. The pure 
substances have been obtained by other methods.” In such hydrocarbons 
the influence of the side-chain is such that in the splitting off of hydrogen 
together with a halogen, or in the combination with a molecule containing 
mobile hydrogen, the latter splits off from, or combines preferably with, 
the carbon atom furthest removed from the side-chain, whilst the electro- 
negative element combines with the carbon nearest the side-chain. 
1:1 : 3-trimethyl-A*-tetrahydrobenzene.® 
Hydroxy-derwatives.—The reaction introduced by Sabatier and Sen- 
derens has been extended to the preparation of aromatic alcohols. When 
phenol is passed together with excess of hydrogen over reduced nickel at a 
temperature of 140°-160°, pure hydroxyhexahydrobenzene is obtained ; 7 
but if the temperature be raised to 215°—230°, the hydroxyhexahydro- 
benzene first formed is decomposed into ketohexahydrobenzene and 
hydrogen. From the mixture so produced Sabatier and Senderens have 
obtained the pure alcohol or ketone by, in the first case, passing the pro- 
duct with excess of hydrogen over reduced nickel at a temperature of 
140°-150°, and in the second by passing the product without hydrogen 
over reduced copper at a temperature of 330°. Under similar conditions 
thymol and carvacrol are converted into the corresponding hexahydro- 
derivatives (Brunel). 
Todohydroxyhexahydrobenzene gives, when treated with potash or 
silver oxide,’ the internal oxide of 1 : 2-dihydroxyhexahydrobenzene, 
fy) 
ScH—cE, 
cH Sou, 
\cu,—CH, 
1 Compt. Rend., 1903, 187, 240. 2 Bull. Soc., 1903, 29, 974. 
3 Cent. Blatt., 1904 (1), 1345. 4 Cent. Blatt., 1904 (1), 1346. 
5 Cent. Blatt., 1903 (2), 289; 1904 (1), 1213; Wallach, Annalen, 1903, 329, 368. 
6 Harries and Weil, Ber., 1904, 37, 848, 
7 Holleman, Cent. Blatt., 1904 (1), 727; Brunel, Compt. Rend., 1903, 187, 1268 ; 
Sabatier and Senderens, ibid., 1903, 137, 1025. 
8 Brunel, Compt. Rend., 1903, 187, 62. 
