Arsenal herbicide, the active ingredient of which is imazapyr [2-(4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl)nicotinic acid], is an imidazolinone type of herbicide. Photodegradation of imazapyr 14C labeled at the carboxyl and 5-oxocarbon positions was carried out separately under borosilicate-filtered xenon arc light at 25 °C in aqueous media. Imazapyr was shown to photodegrade rapidly and extensively in aqueous solution. The decline of imazapyr concentration in the solution followed first-order kinetics. The half-lives were calculated as 1.9-2.3 days in distilled water, 2.7 days in pH 5 buffer, and 2.3 days in pH 9 buffer. The predominant photolysis products derived from carboxyl-14C-labeled imazapyr were 7-hydroxyfuro [3,[4][5][6]pyridin-5(7H)-one and 2,3-pyridinedicarboxylic acid. Decarboxylation was evident as a minor photodecomposition product of carboxyl-14C-labeled imazapyr. Two cyclized compounds, 2,3-pyridinedicarboximide and furo [3,46] pyridin-5(7/i)-one, were also detected as minor degrádales. The one major photolysis product of the 5-oxo-14C-labeled imazapyr was the volatile 14CC>2.

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O,O,S-Trimethyl phosphorothioate, an impurity in several technical organophosphorus insecticides, when administered orally to rats at single doses as low as 15 mg/kg caused delayed mortality, with death occurring 4-22 d after treatment. Delayed toxic signs were also observed in mice, but mice were generally less sensitive than rats. O,O,S-triethyl phosphorothioate and O,S,S-trimethyl phosphorodithioate induced the same signs of intoxication at slightly higher doses. Rats treated with O,O,S-trimethyl phosphorothioate refused food and water within 24 h after treatment and did not eat or drink until the time of death. Neither injection of nutrient solution nor atropine served to reduce or block intoxication. However, the isomeric O,O,O-trimethyl phosphorothioate was a potent antagonist of the toxicity of O,O,S-trimethyl phosphorothioate. As little as 1% of the O,O,O-trimethyl isomer protected rats from the intoxicating effects of the O,O,S-trimethyl isomer at doses as high as 200 mg/kg. Rat serum carboxylesterase and cholinesterase were inhibited for prolonged periods after a single oral dose of O,O,S-trimethyl phosphorothioate, but the duration of inhibition was significantly less when the toxicant contained 1% O,O,O-trimethyl isomer.

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AMDRO fire ant insecticide, the active ingredient of which is AC 217,300 [hydramethylnon; tetrahydro-5,5-dimethyl-2(lfi)-pyrimidinone [3-[4-(trifluoromethyl), is an amidinohydrazone type of insecticide. Photodegradation of AC 217,300 I4C labeled at the benzylic and pyrimidine-2 positions was carried out separately under borosilicate-filtered xenon arc lamps at 27 °C as a suspension in distilled water. AC 217,300 degraded rapidly in water under the light. The half-life of AC 217,300 was calculated as 42 min. The photoproducts of AC 217,300 were characterized with both 14C-and 13C-labeled starting materials. Identifications of the photolytic products were accomplished by CIMS in both the PI and NI modes along with the HPLC and TLC of the photoproduct with the standard reference compound. Compounds l,5-bis(a,a,a-trifluoro-p-tolyl)-l,4-pentadien-3-one (photoproduct 1), , , -trifluoro-p-toluic acid (photoproduct 2), and p-(trifluoromethyl)cinnamic acid (photoproduct 3) were characterized as photoproducts of benzylic 14C-labeled AC 217,300. In addition, 6,7,8,9-tetrahydro-7,7-dimethyl-3-[p-(trifluoromethyl)styryl]-4Ji-pyrimido[2,l-c]-os-triazin-4-one (photoproduct 4) was characterized as a photoproduct from both benzylic and pyrimidine-2 14C-labeled AC 217,300.

for 25 suggests that the RSP flies are capable of detoxification by other mechanisms. In this regard the LD50 of 25 synergized with 5:1 piperonyl butoxide for the SNaidm strain was 7.5 Mg/g. The results indicate that 25 is detoxified to a small extent by the mixed function oxidase enzymes.Except for the trifluoromethyl derivative (26), the other analogues also showed insecticidal activity but none were as potent as 25. The absence of insecticidal activity of 26 and 27 again points out the deactivating influence of the trifluoromethyl moiety in the Z position. Because of the variety of substitutions which were made relative to the original DDT molecule it was not possible to analyze the data by multiple regression analysis (Fahmy et al., 1973). However, comparison may be made with some of the compounds in Table II with those of the DDT type in which Z is trichloromethyl and L is hydrogen. The direct analogue of compound 25 is l,l,l-trichloro-2,2-bis(pethoxyphenyl)ethane. The housefly LDi50 and Culex larvae LC50 of this compound are 7.0 µ%/% and 0.04 ppm, respectively. While 25 is slightly less toxic to these insects than the corresponding DDT analogue, the toxicities are close enough to support the rationale used for the synthesis of these compounds. A similar comparison may be made with compound 21 and l,l,l-trichloro-2-p-chlorophenyl-2-p-anisylethane (housefly LDy, 41.5 Mg/g and Culex larvae LC50 0.058 ppm).Although the insecticidal activities of the compounds in Table II appear to be slightly less than their related DDT analogues, the results, nevertheless, indicate that derivatives which contain an -methyl group also may possess high insecticidal activity. To our knowledge, this is the first case where significant insecticidal activity has been demonstrated with compounds of this type. It should be pointed out that the present study was exploratory in nature and only a few compounds were synthesized and evaluated. The approach, however, appears to be worthwhile and a large number of related derivatives remain to be examined. Further work is in progress.