ox THE STUDY OF HYDRO-AROMATIC SUBSTANCES. 227 



discussed, compared with other closely related compounds, and shown to 

 support the above conclusions as to their constitution. 



Ketohexahydrobenzene is acted on by dry hydrogen chloride ^ to give 

 a substance having the formula Ci2H,nOCl, which loses the elements of 

 hydrogen chloride to give cyclohexene-2-cyclohexanone. 



O 



When this dicyclic ketone is reduced it yields the corresponding saturated 

 alcohol, and this, by treatment with hydrogen iodide, the fully hydro- 

 genised dicyclohexy 1 C^H , , . CgH , , . 



^1 /coAo/,«.— Aromatic quinones ■^ give, when treated with hydrogen in 

 presence of reduced nickel, a variety of products, the nature of which 

 depends largely on the reaction temperature ; if moderately low the 

 dihydric alcohols of the hexahydrobenzene series are formed. 



INIonohydric alcohols may be obtained ■' by the action of various alkyl 

 magnesium iodides on eth3'l hexahydrobenzoate. The latter is readily 

 prepared by treating cyclohexylmagnesium iodide with carbon dioxide.^ 



Ketones. — The action of light on ketohexahydrobenzene and the three 

 isomeric ketomethylhexahydrobenzenes has been studied by Ciamician 

 and Silber,^ who find that the ring is broken with production of a fatty 

 acid containing the same number of carbon atoms together with the 

 corresponding unsaturated aldehyde. 



Not only ketohexahydrobenzene itself,"' but also a number of other 

 simple ring ketones, such as ketomethyl- and ketoraethylisopropylhexa- 

 hydrobenzerie are found to be capable of reacting in the enolic form.'' 



The influence of a very reactive agent, for example acetic anhydride, 

 is necessary to bring about the change and the resulting acetates are 

 converted on saponification into the original ketones. 



Homologues of ketohexahydrobenzene may be prepared ^ by the slow 

 distillation of the anhydrides of substituted pimelic acids. 



Ketohexahydrobenzene and the three isomeric ketomethylhexahydro- 

 benzenes condense with ethyl a-chloropropionate * in presence of sodium 

 ethoxide, to the corresponding glycidic esters, the product in the first 

 case having the formula 



<; 



^C— C.COOCjH,. 

 O CH,. 



On saponification these esters give free acids, which decompose on 

 distillation in a vacuum giving hexahydroacetophenone or its homologues. 

 This latter ketone is, however, best prepared ^ by treating the magnesium 

 compound of cyclohexyliodide with acetaldehyde, and oxidising the 



' WalJach, Ber., 1907, 40, 70. 



'^ Sabatier and Mailhe, Compt. rend., 1908, 146, 4.57. 



=• Hell and Schall, Ber., 1907, 40, 4162. ■• Reports, 1907, 110. 



* Ber., 1908, 41, 1071. « Mannich and Hanen, Ber. 1908, 41, 564. 



' Blanc. Covijpt rend., 1907, 144, 1.^56. • Darzens, Coiwpt. read., 1907, 144, 1123. 



» Hell and Schall, Ber., 1907, 40, 4163. 



q2 



