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UBC Theses and Dissertations

Chelate compounds as seed protectant fungicides and the evolution of toxic gases from chelate fungicides related to dithiocarbamic acid Lopatecki, Leighton Eugene


An attempt was made to create effective fungicides by combining fungistatic chelates with mercury and other metals. Two chelates, cupferron and phenyl-thiodantoic acid, were found highly fungistatic, and the effectiveness of their mercury complexes as seed protectants was similar to that of the standard fungicide Arasan. The mercury complex of cupferron was found relatively unstable, and mercury was easily displaced by metals forming more stable complexes. On the other hand, mercury could not be displaced from the phenyl-thiohydantoic acid complex, and fungistatically, this compound appeared to function as an undissociated molecule. Slopes of dosage-response curves of both chelates were decreased by the inclusion of mercury, and the efficiency of both compounds increased as respiration inhibitors. However, both chelates and their mercury complexes were more effective growth inhibitors than respiration inhibitors, and their fungistatic values could not be estimated by respiration methods. Evolution of toxic gases from dithiocarbamate chelate fungicide during decomposition was measured in the Warburg manometer. It was concluded that the dialkyl series of dithiocarbamates decomposed in the presence of slightly acid buffers to produce carbon disulphide and a dialkyl-amine. Dithane, on the other hand, decomposed with evolution of hydrogen sulphide and carbon disulphide, and, it was assumed, with a residue of ethylene thiourea.

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