ON THE CONSTITUTION OF CAMPHOR. 307 



The six forms of camphoric acid are completely explained on the 

 assumption that in the molecule there arc two asymmetric carbon atoms 

 which are not equivalent. Designating the two carbon atoms by the 

 letters A and B, the six forms may be represented by the combinations, 

 no internally compensated form being possible : 



(A,,B,,) and (A,B()--<^- and /-camphoric acid. 

 (A,,B,,) and (A,,B,)...f?- and /-isocamphoric acid. 

 (AjB^, + A,B,)... Inactive camphoric acid. 

 (AjB.j + A^B,)... Inactive isocamphoric acid.^ 



It does not appear that the sign of both asymmetric carbon atoms can 

 be revei'sed by simple means, but J-isocamphoric acid may be obtained 

 from c?-camphoric acid fairly readily ; as, for example, by treatment with 

 phosphorus pentachloride and water successively, whilst the reverse change 

 may also be effected by suitable means, such as boiling with acetyl 

 chloride, or by the process of bromination, when ordinary bromocamphoric- 

 anhydride is obtained. 



The readiness with which one of these asymmetric carbon atoms is 

 affected makes it seem certain that this must be the atom on which a 

 carboxyl group and a hydrogen atom are attached, as there is here the 

 only grouping where the existence of tautomerism, or simple internal 

 change, appears possible. A glance at the simple scheme for camphoric 

 acid, moreover, 



CH . COOH 



C.COOH 



c 



makes it appear highly probable that each carboxyl group is an attach- 

 ment to one or other asymmetric atom, and the difficulty of conceiving 

 any simple internal change which would affect the condition of the second 

 asymmetric atom accounts sufficiently well for the non-occurrence of 

 inversion in this instance. 



The occurrence of only two enantiomorphously related camphors is 

 probably dependent on stereochemical considerations, analogous to the 

 non-formation of anhydrides from ^raws-dicarboxylic acids of the poly- 

 m ethylene series. 



E.— DEGRADATION OF CAMPHOR DERIVATIVES. 



Whilst the material which has already been dealt with affords us much 

 useful evidence regarding the structure of the ketone ring, there is little or 

 none of it which afibrds us any assistance in coming to any conclusions 

 regarding the hydrocarbon ring. In order to gain any conception as to 

 the structure of the second nucleus it becomes necessary to consider the 

 nature of products which are obtained when this ring is broken down in 

 various ways. 



It will be convenient to refer to each of the various modes in turn, 

 and to consider the constitution of the products of known character as 

 they come under consideration. 



' Aschan, Acta soc, Sci.fennicte, SI, 1. 



X2 



