Plant Qrowth'Suhstances 



Methyl-ketole (2-methyl-indoIe) and skatole (3-methyl- 

 indole) converted into Grignard magesium halogenides, form 

 the respective 2- or 3-methyl-i-carboxy acids when treated 

 at room temperature with COg. If the CO2 is passed in at the 

 temperature of boiling toluene, the magnesium halogenide of 

 2-methyl-indole forms only 2-methyl-3-carboxy-indole. The 

 magnesium halogenide of skatole persists in yielding the i(N)- 

 carboxy compound when treated with COg even at 20o°C., 

 and a bath temperature of about 310° is necessary for the 

 carboxy group to become attached in the 2-position (3-methyl- 

 2-carboxy-indole) instead of in the i -position. 



Indolyl magnesium halogenides commonly form 3-sub- 

 stituted alkyl derivatives from alkyl halogenides, though sub- 

 stitution in the i -position may occur. 



The preparation of many indole derivatives, including 

 those mentioned in the foregoing paragraphs, and also 3- 

 acetyl-indole (3-indolyl-methyl-ketone) and homologues, has 

 been described by Oddo (1921 ). Some of his descriptions are 

 reproduced in Houben's "Die Methoden der organischen 

 Chemie," 2nd. edn., Leipzig, 1924; Vol. IV, p. 882. 



i-methyl-indole-3-carboxylic acid, from treatment of 

 methyl-phenylhydrazine-pyroracemic acid with hydro- 

 chloric acid: Hartley and Dobbie (1899). 



i-methyl-indole-3-acetic acid: Piccinini (1899). See p. 106. 



Few of the above-mentioned substances have been tested 

 on plants, but they are mentioned for the sake of complete- 

 ness in view of their possible synthetic or constitutional 

 importance. 



Still other synthetic compounds have been submitted to the 

 Avena and other tests by Kogl and Kostermans (1935), 

 Haagen-Smit and Went (1935 F) and others. Lists of their 

 results are given in Boysen Jensen's book. 



The growth-regulating value of salts of synthetic acids has 



110 



