ON THE STUDY OP HYDRO AROMATIC SUBSTANCES. 81 



their hydrocarbon possesses physical properties identical with those of 

 1 : 1-dimethylcyclohexane prepared from dimethyldihydroresorcin,^" but 

 state that it gives on treatment with bromine in presence of aluminium 

 bromide, tetrabromo-p-xylene, melting at 256°. Eecent work has shown 

 that 1 : 1-dimethylcyclohexane may be prepared from acetylmethyl- 

 heptenone as a starting-point. This hydrocarbon, on treatment with 

 bromine in presence of aluminium bromide, does not give tetrabromo-p- 

 xylene, as stated by Zelinsky and Lepescbkin. Further, 1 : 1-dimethyl- 

 cyclohexane on treatment with a mixture of nitric and sulphuric acids 

 gives the two isomeric trinitrb-o-xylenes, melting at 72° and 115° re- 

 spectively, which proves that, as in so many instances already recorded, 

 the methyl group has again wandered into an ortho and not a para 

 position. 



Dynamic Isomerism. — Report of the Committee, consisting of 

 Professor H. E. Armstrong {Chairman) , Dr. T. M. Lowrv 

 {Secretary), Professor Sydney Young, Dr. G. H. Desch, 

 Sir J. J. DoBBiE, and Dr. M. 0. Forster. {Drawn up hy 

 the Secretary.) 



a'-Chlorncamphor.^ 



During the past year the principle of dynamic isomerism has been 

 applied in preparing, in a pure state and in considerable quantity, the 

 first member of a hitherto unisolated series of halogen derivatives o' 

 camphor, a-chlorocamphor, as Kipping found in 1905, becomes iso- 

 dynamic with the stereoisomeric a'-chlorocamphor when alkali is pre- 

 sent; when the alkali is removed the isomerism again becomes static, 

 and the isomerides can be separated by ordinary methods of fractionation, 

 a'-chlorocamphor presents several points of special interest : — 



First. It lies on the borderland between the more labile and the 

 wholly stable forms of isomerism ; if proper precautions are taken, the 

 a'- compound can be kept an indefinite time, but if carelessly handled 

 [e.g., if crystallised from a medium containing traces of alkali) it may 

 at any time revert to the less soluble and therefore more stable a- com- 

 pound. 



Second. When brominated it gives a mixture of stereoisomeric 

 oa'-bromochlorocamphors in exactly the same proportions as when 

 a-chlorocamphor is brominated, i.e., the position taken up by the bromine 

 is not affected in the least by the position which the chlorine atom 

 occupies. This remarkable result is in agreement with Lapworth's 

 view that in the bromination of ketones it is an enolic isomeride that 

 is first attacked ; more generally we may conclude that at some stage 

 in the bromination a and a'-chlorocamphor give rise to some identical 

 intermediate product. 



Third. In complete contrast with their behaviour on bromination, 



'0 J.C.S.. 19)5. 87. 1487. 



' The experiments on a'-chlorocamphor have been made by Mr. Victor Steele, and 

 are described in detail in a joint paper recently communicated to the Chemical 

 Society. 



1915. Q 



