[Phytotoxic activity of asymmetric 3,4-dichlorobenzoic acid dialkylamides].

The phytotoxicity of asymmetric N,N-dialkyl-3,4-dichlorobenzamides was studied in pre- and post-emergence tests against some weed species. The amide groups were characterized by the presence of a sec.butyl or 1-methylbutyl group and a variable second alkyl group either linear, branched, saturated or unsaturated. Isomers of the above compounds were also prepared and tested as useful comparison materials; these isomers have n.butyl or ter.butyl in place of sec.butyl or a 1-ethylpropyl in place of 1-methylbutyl or other branched alkyl groups with 5 or 6 carbon atoms, always having a methyl group in the alpha position, in place of the 1-methylbutyl and a second substituent in C2 leads to C4. The results show that compounds with phytotoxicity and selective action as regards Echinochloa and Setaria are obtained if a sec.butyl group, a 1-methylbutyl or a 1-ethylpropyl group is retained and the second substituent on the N-amide is varied appropriately. The compounds with greater phytotoxicity towards the weeds were further tested against some species of agricultural interest.