220 CHEMICAL DISCOVERY AND INVENTION 



The first compounds of this type were obtained in 1909 by 

 Professors Perkin, Pope, and Wallach, and one of them is 

 represented by the formula below : 



CH 3 \ /CH 2 .CH 2 \ /H 



H/ \CH 2 -CH 2 / CO-OH 



Here there is no carbon atom which is asymmetric according 

 to Van 't Kofi's definition ; nevertheless it is obtainable in a 

 right-handed and left-handed form, which may be accounted 

 for by supposing the two groups at one extremity to lie in the 

 plane of the paper, while the other two stand the one above and 

 the other below the paper. 



But at this point the difficulties of the problems involved 

 multiply to such an extent that without a considerable acquaint- 

 ance with the complicated, and in some cases imperfectly known, 

 compounds of carbon it would be impossible to communicate 

 further information on this most interesting department of 

 chemistry. Moreover for complete demonstration models are 

 necessary. For the student, therefore, who desires to pursue 

 the study of stereo-chemical theory the larger treatises and the 

 current periodical literature must be appealed to. 



It may, however, be interesting to the general reader to learn 

 what progress has been made in the application of space chemis- 

 try to elements other than carbon, which so far has alone been 

 referred to. 



Nitrogen presents itself first, and a case of nitrogen asymmetry, 

 corresponding to carbon asymmetry, has been observed by Le 

 Bel in the compound methyl-ethyl-propyl-isobutyl ammonium 

 chloride : 



CH 3 .C 2 H 5 .C 3 H 7 .C 4 H 9 NC1 



Here the four radicles are attached in the same kind of way 

 to the nitrogen, and in accordance with the principles already 

 explained there may be two arrangements, one of which is the 

 mirror image of the other. 



A few years later, in 1899, a compound of similar constitution 

 was obtained by Professor Pope and Mr. Peachey and resolved 

 into optically active dextro- and Isevo- compounds. 



It is uncertain whether the centre of mass of the nitrogen 

 atom should be supposed to occupy one solid angle of a regular 

 tetrahedron, three of the valencies acting along the edges of the 



