470 SCIENCE PROGRESS 



taste, which resembles that of peppermint. The two con- 

 figurations are shown below : 



CH3-C-NH, NH,,-C-CH3 



I! ' il 



C,H,-CH,-C-COOEt CgHs-CHo-C-COOEt 



A similar example is found in the case of the aldoximes : the 

 syn-form of anisaldoxime is tasteless, while the anti-form is 

 very sweet : 



CH,.O.C,H,-C-H CH3.0.C,H,-C-H 



II II 



N-OH HO-N 



Syn-form Anti-form 



We must next deal with another case in which the rotation 

 of carbon atoms about their axis of junction is hindered. When 

 three or more carbon atoms are joined together to form a cyclic 

 compound like trimethylene : 



CH, 



CH, CH, 



there are two important consequences. In the first place, free 

 rotation of the carbon atoms becomes difficult, if not impossible. 

 This can be seen b}- building up a model, when it will be found 

 that a disruption of the molecule would almost certainly result 

 from any such rearrangement. Secondly, the six hj-drogen atoms 

 in trimethylene are arranged in two parallel planes, the carbon 

 atoms lying in a third plane between these two and parallel to 

 them. 



