265 



Indeed, a closer examination of the stereometrical model of this 

 molecule will clearly show, that it is completely asymmetrical: 



/A 



Therefore, its configuration must be different from its mirror- 

 image, although no true asymmetric carbon-atoms are present here. 

 Examples of the special case where a carbon-atom links two rings, 

 have been given already on page 260. 



Especially in cyclic compounds, the presence of such double bonds 

 can be of interest for the question of the resolvability of the molecule 

 into optically active antipodes. 



Pope, Perkin and Wallach x ) prepared and studied the i-methyl- 

 cyclohexylidene-^.-acetic acid : 



H 



This molecule has no symmetry at all, and indeed it appeared 

 to be resolvable into optical antipodes by the aid of brucine. 



The dibromo-zddit ion-compounds preserved their activity also, 

 and the same was found for the corresponding hexanes. The p-dextro- 

 acid could be obtained in tetragonal crystals, measured by Halli- 

 mond, but these did not exhibit any trace of hemihedrism. 



A case similar to this, is that of ^.-oximino-cyclohexane-carboxylic 

 acid : 



:N OH 



!) W. J. Pope, W. H. Perkin Jr., and O. Wallach, Journ. Chem. Soc. Lon- 

 don, 95, 1789, (1909); W. J. Pope and W. H. Perkin Jr., Journ. Chem. Soc. 

 99, 1510, (1911); A. E. Everest, Chem. News, 100, 295, (1909); J. E. Marsh, 

 Proceed. Chem. Soc., 27, 317, (1911); P. F. Frankland, Journ. Chem. Soc. Lon- 

 don, 101, 654, (1912). 



