The N-Arylphtlialamic Acids 269 



on activity in all three biological responses. Both ortlio and meta 

 substitution of chloro- or methyl- groups enhanced the activity of N- 

 phenylphthalamic acid, and the 2,3- and 3,5-dichloro-, and the 2,3,5- 

 trichlorophenylphthalamic acids were the most active tested. In con- 

 trast, para and di-ortho substituents either abolished or had no effect 

 on biological activity. While some of these substitutive effects sug- 

 gested similarities to either the benzoic, phenylacetic, or phenoxyacetic 

 acids, others showed distinct differences. 



In view of the molecular structure-biological activity relationships 

 in the N-arylphthalamic acids, continued study of this group of com- 

 pounds should provide valuable information on the fundamental 

 chemical structure requirements for plant growth regulating activity. 



ACKNOWLEDGMENT 



The work reported was supported in part by a Grant-in-Aid from 

 the Naugatuck Chemical Division, U. S. Rubber Company, Nauga- 

 tuck, Conn. The authors are also indebted to this company for sup- 

 plying the chemicals used in these studies. 



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