Naphthyloxy compounds as plant growth regulators 



successive /^-oxidations it could be converted by the plant into the biologically 

 active 2:4-dichlorophenoxy acetic acid, thus: 



CV 



OCH2CH2C4H2CH2 



CI 



a 



CH2COOH 



CI 



/5 • a 

 OCH2CH2 CH2COOH 



CI 



CI 



OCH2COOH 



CI 



Those members of the series with an odd number of carbon atoms, on the 

 other hand, would be oxidized via the hypothetical carbonate to 2:4- 

 dichlorophenol, which is inactive as a growth regulator. 



•CHoCOOH r ^x .OCOOH1 ^v ^OH 



CI 



OCR 



CI 



LCI 



CI 



CI 



CI 



This hypothesis has received strong support from the work of Fawcett, 

 Ingram, and Wain (1952), who produced evidence for the production of 

 phenol in flax plants treated with oj-phenoxyalkyl carboxylic acids with an 

 odd number of carbon atoms in the side-chain. Wain and Wightman (1954) 

 have also demonstrated indirectly the /5-oxidation within the plant of 

 similar compounds with an even number of carbon atoms in the side-chain. 

 The results presented in this paper for the fo-(2-naphthyloxy)-tt-alkyl 

 carboxylic acids are in good agreement with those of Synerholm and 

 Zimmerman (1947) and Wain and Wightman (1954) and it seems likely 

 that a similar mechanism is operative. The reduced activity of the 8, 10, 

 and 12 carbon atom members compared with 2-naphthyloxyacetic acid 

 requires special comment, since if the /j-oxidation hypothesis is correct these 

 compounds, like the 4 and 6 carbon members, would be expected to show a 

 relative molar activity of 1000. As can be seen from the table, there is a 

 marked falling off in the water-solubility of the compounds having more than 

 8 carbon atoms in the side-chain. It seems unlikely, however, that this can 

 be considered as a contributory cause of their lower activity for even at 

 concentrations at which they formed true solutions in water, their activity was 

 much less than would have been expected on the assumption of complete 

 oxidation to 2-naphthyloxyacetic acid. Further confirmation of the fact that 

 biological activity and water solubility are not directly related is provided by 

 the two dimorphic forms of e-(2-naphthyloxy)-n-caproic acid which in spite 

 of a very great difference in solubility both gave an activity of 1000 in the 



197 



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