Plant Qroxvth'Suhstances 



The ethyl naphthalene-glyoxylate, and the naphthalene- 

 glycolHc and -acetic acids were stated to exhibit plant growth- 

 regulating properties in varying degrees, but the details of 

 the physiological experiments have not yet been published. 



Higher Aryl Compounds 



These are included in the only set of examples of the pro- 

 duction of growth-regulating substances protected by patent 

 (Wolfram et al., 1934). 



Anthracene-acetic, fluorene-acetic, and acenaphthene-5- 

 acetic acids can be prepared by heating the hydrocarbons with 

 chlor-acetic acid. The yields are small, but Zimmerman and 

 Wilcoxon (1935) found that they could be improved by adding 

 aluminium chloride to the melt. The location of the substi- 

 tuents in the anthracene and fluorene compounds is not 

 known. 



An Important Hint 



In this series of indolyl and related syntheses it has been 

 customary to aim at the preparation of the pure acids, often 

 via an alkyl ester subsequently hydrolyzed. In view of work 

 by Zimmerman, Hitchcock, and Wilcoxon (1936) it is doubt- 

 ful whether the sometimes troublesome isolation of the free 

 acid is necessary or desirable. These authors have shown that 

 several esters belonging to the series of phenyl-acetic, 

 naphthyl-acetic and indole-fatty acids are quite effective in 

 initiating or otherwise affecting growth of organs and cells in 

 plants. Methyl 3-indole-acetate indeed, was more effective 

 in this way than was the free acid: the "natural" "hetero- 

 auxin". The same authors state that there is no evidence at 

 hand that hydrolysis of these esters to acids occur in plant 

 tissues. It has, however, been shown by Zimmerman and 

 Wilcoxon (1935) that a-naphthalene-aceto-nitrile was not 

 only not poisonous to plants, but was very effective physiolo- 

 gically in the same respects as was the free acid derivable from 

 it by hydrolysis in the laboratory.^ 



^ The nitrile was more effective in root-production on stems of large 

 plants than was the free acid at the same concentration. 



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