Halogeno-o-phenylenediamines and Derived Heterocycles.
Test-plots of strawberries, sugar beet, hops and brussels sprouts were sprayed with the mixed insecticide, made radioactive by synthesizing it from at various times from May to October. The insecticide sprayed contained roughly equal proportions of octamethylpyrophosphoramide, (Me,N),P,O,. and its higher homologue, (Me,N),P,O,.On analysing the sprayed crops at various times after spraying it was found that the concentration of both constituents in the plant fell at much the same rate, and that this rate varied little amongst the plant species treated providing all were treated at the same time of year. The rate slowed somewhat, however, as the year progressed from May to September, and became very slow indeed in October.It is likely that practically the whole lowering of concentration with time is attributable to this decomposition.It was also shown that the plants decomposed the insecticide.The insecticide Pestox I11 can be regarded as a mixture of two insecticides, R,P30, and R4P203 (R = Me,N-) (Parts I and 11). It has long been realized that the systemic activity of this mixture, and of the constituents separately, is far more transient than would be expected from the high stability of the constituents in water, acids and alkalis (Heath & Casapieri, 1951). The aphid kill has generally been found to cease 3-5 weeks after leaf application (Ripper, Greenslade & Lickerish, 1949 ; Ripper, Greenslade & Hartley, 1g50), whereas the half life of RSP30,, the less stable of the two, is about two years at typical plant pHs.These insecticides are then decomposed in the plants by mechanisms other than normal hydrolysis. Presumably some enzymic system brings about decomposition (Hartley & Heath,The authors therefore prepared Pestox I11 in radioactive form from s2P, in order to study the decomposition in plants at different times of the year. The aims of the research were, first, to discover any generalities about rate of decomposition, and secondly, to try to throw some light on its mechanism. The experiments directed to the first aim are described in this paper, and those directed to the second in Part IV. Outline of methodRadioactive R4P203 and R5P30, were prepared, and were sprayed on small test-plots of crops. Samples of the crops were taken a t a series of known times after spraying, and analysed for R,P,03, R,P305 and decomposition products.Dahlia plants were subjected to root treatment by applying the insecticide to the soil in which they were growing. Preparation of radioactive insecticideDry red phosphorus is irradiated by A.E.R.E., Harwell, to an activity of about 7 mc./g., and converted to phosphoryl chloride via phosphorus pentachloride by the action of chlorine and water. The phosphoryl chloride is converted to pyrophosphoric acid tetradimethylamide, etc., by the methods described in Part I, which gives a product contaminated with free tertiary amine and R3P0. The tertiary amine and R3P0 are removed by fractionating them out at I mm. pressure. Non-radioactive R3P0 is then added, and the fractionation repeated. ...
Sugar beet and strawberry plants were treated with octamethylpyrophosphoramide, R4P2O3, and tri(dimethylamino)phosphine oxide, R3PO [R = Me2N‐], containing 32P. Both are decomposed at similar rates in both sugar beet and strawberries. When sugar beet treated with R4P2O3 were analysed 10–14 days after treatment, it was shown that the 32P in the beet existed only as unchanged R4P2O3 and products not extractable from water by chloroform. When R3PO‐treated‐beet were analysed it was found that, besides unchanged R3PO and non‐chloroform‐extractable compounds, some of a compound less extractable than R3PO by chloroform was produced. The way these results bear on the mechanism of decomposition of R3PO and R4P2O3 in the plant is discussed.
Dialkoxyphosphinothioylthioacetamides may be prepared conveniently in good yields and high purity from the reaction between dialkoxyphosphinothioylthioacetic acetic anhydrides and the appropriate amine. The necessary mixed anhydrides were readily prepared under very mild conditions by allowing keten to react with a dialkoxyphosphinothioylthioacetic acid in acetone. The method was applied to the preparation of both dimethoxy-and diethoxyphosphinothioylthioacetic anhydrides. The former was then interacted with methylamine to yield N-methyl dimethoxyphosphinothioylthioacetamide (dimethoate) or with morpholine to yield N-(dimethoxyphosphinothioylthioacetyl) morpholine. The diethoxy compound was converted to diethoxyphosphinothioylthioacetamide with ammonia. An alternative approach via the acid halides was examined. For this purpose dimethoxyphosphinot hioylthioacetyl chloride and diethoxyphosphinothioylthioacetyl chloride and fluoride were prepared. They could not be obtained pure. The alkaline hydrolysis rates of dimethoxy-and diethoxyphosphinothioylthioacetic acids were determined and the acid dissociation constant of the latter compound was obtained by two methods.
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