Substituted Benzoic Acids 



257 



Table 1. Activities of chloro- and methyl-substituted benzoic acids in the pea 

 curvature test. * 



Substituted 

 Benzoic Acid 



2-Chloro-. . . . 



3-Chloro- 



4-Chloro- 



2,3-Dichloro-. 

 2,4-Dichloro- 



2,5-Dichloro-. . 

 2,6-Dichloro-. . 

 3,4-Dichloro- . . 

 3,5-Dichloro-. . 

 2,3,6-Trichloro- 



2-Methyl- 



3-Methyl- 



4-Methyl- 



2,3-Dimetiiyl- . 

 2,4-Dimethyl- . 



2,5-Dimethyl- . 

 2,6-Dimethyl- . 

 3,4-Dimethyl- . 

 3,5-Dimethyl- . 



Molar Concentrations 



10-7 





 

 

 

 





 

 

 

 





 

 

 

 





 

 

 



io-« 









 

 

 





 

 

 

 3 





 

 

 

 





 

 

 



10-5 









 

 

 



3 





 

 

 4 





 

 

 

 





 

 

 



10-4 





 

 

 2 

 



5 



1 





 

 5 





 

 



1 









 

 

 



10-' 





 

 

 4 

 



5 

 3 

 

 

 6 





 

 

 4 

 



2 

 1 

 

 



* Activity on an arbitrary scale: = inactive; 6 = highly active. 



Dr. Muir: I would like to make it clear that in the first place we 

 were looking at a series of compounds which we were trying to ex- 

 plain. We found that in the fluorine series we had a rather unusual 

 situation as far as halogen substituents were concerned, and our dis- 

 course was primarily concerned with them. I don't see, except for 

 a few compounds which Dr. Smith studied, any real difference from 

 our position other than in the methyl-substituted compounds. These 

 may yield wholly different results, and until we have further electronic 

 data to analyze this picture, I don't believe they constitute too serious 

 an objection. Our primary purpose was to explain the relationship of 

 structure as it is shown in the effects of these compounds on Avena 

 coleoptile tissue. 



Dr. Wain: I would just like to say again what Dr. Smith has said. 

 All these results have been obtained in three different tests by Dr. 

 Wightman so that the results are of general applicability as far as 

 we can see in these different tests, using different types of tissue. 



Dr. Fawcett: In his discussion of the highly active 2,3,6-trichloro- 

 benzoic acid. Dr. Muir postulates a nucleophilic reaction involving 

 a replacement of the chlorine atom in the 6 position. In 2,3,5,6-tetra- 

 chlorobenzoic acid, which has similar activity, a nucleophilic replace- 

 ment of either of the ortho chlorine atoms would be subject to con- 



