SPACE-ISOMERISM 



77 



four affinities (shown by the full lines) directed towards the 

 four solid angles (shown dotted), thus : 



a 



b c, 



FIG. 17. THE TETRAHEDRON OP THE CARBON ATOM, IN PERSPECTIVE 



If now the four different groups be attached at each of the 

 four angles of the tetrahedron, say, a, b, c and d, it will be seen 

 that a right-hand and left-hand arrangement can be produced 

 thus (Fig. 18) : 



c c b 



FIG. 18. RIGHT- AND LEFT-HAND ARRANGEMENT. l 



1 The following useful suggestion is taken from F. J. Moore's Out- 

 lines of Organic Chemistry (p. 150). The student can readily con 

 struct tetrahedral models from paste- 

 board in the following manner. An 

 equilateral triangle is drawn, each of 

 the three sides bisected and the 

 middle points joined up as shown in 

 Fig. 19. The large triangle is cut 

 out and the corners folded along the 

 dotted lines of the smaller one ; the 

 points at the top are joined up by 

 fine wire or gum paper. By marking 

 the corners differently the simpler 

 relations of space isomerism can easily 

 be studied. FIG. 19. 



