ON THE STUDY OF HYDRO-AROMATIC SUBSTANCES. 63 
Transformations.—1-Methy1-3-ketohexahydrobenzene has been con- 
verted into 1-methyl-2-ketohexahydrobenzene! by the series of reactions 
already described.” 
When 1 :5-dimethyl-3-keto-+!-tetrahydrobenzene * is heated with an 
equal weight of ammonium carbonate, a small quantity of a base is formed 
identical with collidine (2:4:6-trimethylpyridine). The mechanism of 
this process is the exact reverse of Hantzsch’s reaction * whereby dihydro- 
pyridine, under the influence of hydrochloric acid, yields ketotetrahydro- 
benzene. 
Tt has been shown by Demjanow and Luschnikow * that it is possible 
to convert a substance containing a tetramethylene ring into one con- 
taining a pentamethylene ring (cyclopentanol from tetramethylenemethyl- 
amine) ; and, in continuance of this work, Demjanow ° has now provided 
an example of the conversion of a ring containing six carbon atoms into 
one containing seven. On distilling hexahydrobenzamide with phosphorus 
pentoxide it yields cyanohexahydrobenzene (1), which on reduction gives 
the corresponding amine (2). When the hydrochloride of this amine 
CH, - CH, CH,—CH, 
CHK (1) Sex GN CH @), cH . CH, . NH, 
CH, —CH, CH,— CH,” 
oe —OH,=08 - eS 
CH, 
(3) | 
*\ cH, — CH,—CH, 
is acted on with silver nitrite it is converted intoan alcohol identical in every 
respect with suberyl alcohol (3), already described by Markownikoff.’ 
A study of the action of bromine on 3 : 5-dichloro-1 : 1-dimethyl-A?**- 
dihydrobenzene * has shown that the resulting hydro-aromatic bodies very 
readily lose hydrogen bromide to form aromatic substances, of which the 
two principal ones are 3 : 5-dichloro-4-bromo-o-xylene and 3 : 5-dichloro- 
6-bromo-o-xylene. Since the dichlorodimethyldihydrobenzene, which forms 
the starting-point of the research, contains the gem-dimethyl group, the 
migration of one of these methyl groups becomes an essential step in the 
production of an aromatic compound. The reaction has therefore been 
worked out so as to gain an insight into the course of such changes, more 
especially as, on account of the symmetry of the molecule, it forms one of 
the simplest cases in which the wandering of an alkyl group can take 
place. The reaction is largely influenced by the condition of experiment, 
but no substance has been encountered in which an alkyl group has 
wandered into any but an ortho-position. 
The Nature of Double Linkings.—Recent experimental work has 
enriched our knowledge of the behaviour of substances containing double 
linkings, more especially as regards the property of addition. In the 
case of a substance containing several double bonds in the molecule, these 
bonds often do not behave independently of one another. Thiele’s theory ° 
of partial valencies provides a possible explanation of many such cases. 
Knoevenagel '° considers it essential to study the movement of the atoms 
themselves in the molecule, and assumes that doubly linked carbon atoms are 
' Wallach, Annalen, 1903, 329, 368. 2 Reports, 1903, p. 181. 
3 Knoevenagel and Erler, Ber., 1903, 36, 2129. 4 Annalen, 1882, 215, 297. 
5 Cent. Blatt., 1903 (1), 828. 8 Cent. Blatt., 1904 (1), 1214. 
™* Ber., 1893 26, R, 813. 8 Crossley, J. C. S., 1904, 85, 264. 
o~ - Annalen, 1899, 306, 87. 10 Ber., 1903, 36, 2803. 
