Chemical configuration and action. Paste method 



of the revolving groups to one another. These positions, however, are 

 determined by the environs of the molecule, and the nature of these, at site 

 of action, is not known. We also have no information on the required 

 position of the molecule at site of action, nor do we know how to find this 

 active position, which could be supposed to correspond with the gaps of the 

 reacting system. It seems reasonable to assume that different growth 

 substances probably act in the same way on the same cell-elongating svstem, 

 and must therefore be able to assume the same active form. 



Figure 9. Molecular models of some 

 newly discovered growth promoters. 

 Top: 3-amino-triacole. Middle: X- 

 dimethyl-thiwamacetic acid (van der 

 Veen). Bottom: 2-oxy benzthiazole- 

 acetic acid. 



In view of the above considerations, it would seem important to try to 

 find the positions of the more or less free rotating side-chains of different 

 growth substances which show similar activity to one another. A long 

 series of trials with the molecular models constructed by Stuart and Briegleb 

 showing the space occupied by every single atom within the molecule 

 magnified 1:1-5.108, revealed that the main growth substances with 

 acetic acid as a side-chain are able to assume very similar forms. These 

 similarities are shown in Figure 8. For the purpose of this comparison, we 

 selected a standard position of the side-chain relative to the ring- (or body-) 

 system of the molecule. The criterion of this position is that the axis of the 

 end group of the side chain hes at an angle of 90° to the longer axis of the 

 ring-system of the molecule {Figure 13). In the case of 2 : 4 : 5-trichloro- 

 phenoxyacetic acid this position is possible and the COOH-group remains 

 free to rotate even in this position ; in the case of 2 : 4 : 6-trichlorophenoxy- 

 acetic acid, however, this is impossible. We do not know if this selected 



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