266 



which was prepared by Kay and Per kin l ), and which was first 

 split up, by means of morphine, by Mills and Bain 2 ). 



This molecule has apparently a plane of symmetry perpendicular 

 to the plane of the ring, which passes through the groups C0 2 H 

 and the nitrogen-atom. The fact, however, that the English investi- 

 gators succeeded in splitting up this molecule into optical antipodes, 

 seems to indicate that the complex : = N OH is, in some way, situated 

 ^^symmetrically with respect to the plane of the ring, so that the 

 symmetry-plane mentioned above is in reality not present in the 

 molecular configuration. But as an optical isomerism of this kind 

 has never been found in analogous cases, this substance and its 

 derivatives deserve yet a minute and thorough examination. 



Somewhat different, because one of the carbon-atoms may 

 be concerned as asymmetrical, is the case of the fission of the acid: 



which is an isomeride of the acid investigated by Pope, Wall ach, 

 and Perkin, and which melts at 41 C.; it was separated by 

 Marckwald and Meth 3 ) by means of the acid cinchonine-saHts. 

 Some remarks may be made in this connection on the isomerism 

 which, according to some investigators, would occur in ethylene- 

 compounds of a constitution like: 



In general such ethylene-compounds are supposed to be symmetrical 

 with respect to the plane passing through both the double-bound 

 carbon-atoms and all substitutes X, Y, Z, etc. ; the study of a great 

 number of ethylene-deriva.tives seemed hitherto to have confirmed 

 this view. 



However, in the last ten years, Erlenmeyer Jr. pointed out, 



!) F. W. Kay and W. H. Perkin Jr., Journ. Chem. Soc., 89, 1640, (1907). 



2 ) W. H. Mills and A. M. Bain, Journ. Chem. Soc., 97, 1866, (1910). 



3 ) W. Marckwald and R. Meth, Ber. d. d. Chem. Ges., 39, 1175, (1906). 



