Determination of N-(3-ethylsulfonyl-2-pyridinyl)-4,6-dimethoxy-2-pyridineamine in soil after treatment with rimsulfuron

An analytical procedure to detect N-(3-ethylsulfonyl-2-pyridinyl)-4,6-dimethoxy-2-pyridineamine, a degradation product deriving from the hydrolysis of rimsulfuron in soil, has been developed. The analytical standard was prepared by basic hydrolysis of rimsulfuron at pH 9 and purification on a silica gel chromatographic column. The compound obtained was stable at high temperature, thus enabling determination by gas chromatographic analysis. Soil samples were extracted with acetonitrile, purified with a SPE C18 cartridge and analysed using both nitrogen phosphorus (NPD) and mass spectrometer detectors. The analytical procedure described proved to be sensitive and reproducible. Recoveries varied from 84 to 90%. The limit of sensitivity was 0·001 mg kg^-1. © 1997 SCI.     

Kinetics and mechanism of the hydrolysis of imidacloprid

The kinetics of the hydrolysis of imidacloprid were studied at different pH values and under various temperatures. Imidacloprid was found to be stable in acidic and neutral water, but readily hydrolysed in alkaline water. The main hydrolysis product was found to be 1-[(6-chloro-3-pyridinyl)methyl]-2-imidazolidone, and a mechanism for its formation is proposed. © 1999 Society of Chemical Industry     

Studies of the New Herbicide KIH-6127. Part III. Synthesis and Structure–Activity Studies of Analogues of KIH-6127 against Barnyard Grass (Echinochloa oryzicola)*

The previously evaluated prototype, methyl 6-acetyl-2-[(4,6-dimethoxypyrimidin-2-yl)oxy]benzoate, was modified by the introduction of an oximino group. Further extensive synthetic modifications were then made to the 6-alkyl moiety (R¹), the ester moiety (R²), the alkoxyimino moiety (R³), the bridge-atom (X) and the 4,6-disubstituted-pyrimidine moiety (A, B, Z). Structure–activity relationships of the synthesized compounds were studied by examining their herbicidal activity against Barnyard grass (Echinochloa oryzicola) in paddy rice at various growth stages, including pre-emergence. The novel herbicide methyl 2-[(4,6-dimethoxypyrimidin-2-yl)oxy]-6-[1-(methoxyimino)ethyl]benzoate, (KIH-6127) was found to be the most effective compound. The commercial development of this compound is currently in progress. © 1997 SCI.     

Hydrolysis of the pyrethroid insecticide fenpropathrin in aqueous media

The hydrolysis of [¹⁴C] fenpropathrin ( I ) [(RS)-α-cyano-3-phenoxybenzyl 2,2,3,3-tetramethylcyclopropanecarboxylate] was studied in buffer solutions at pH 1.9–10.4, and in natural river and sea water at 25, 40, 55 and 65°C under laboratory conditions. The hydrolysis of I proceeded predominantly through neutral (pH independent) and base-catalysed processes in the regions below pH 3.9 and above pH 7.0, respectively, whereas both reactions occurred between pH 3.9 and 7.0. The rates of hydrolysis of I in buffer solutions were similar to those in one sample of river and one sample of sea water. If this obtains generally, it may be expected that the half-life of I in natural waters, normally within the range pH 5–9, will range from 1.54 to 1080 days at 40°C, 11.3 to 8520 days at 25°C and, by extrapolation of the data obtained in buffer solutions, 106 to 83 000 days at 10°C. The rate constants for hydrolysis of I in aqueous media can be expressed by: Where log k_N = 9.60–(5.56 × 10³ T^?1) and log k_B = 7.32–(2.56 × 10³ T^?1). The calculated rate constants were in good accord with the observed values in buffer solutions. Cleavage of the ester linkage was more rapid than hydration of the cyano group at any pH and temperature tested.     

嘧啶联吡唑甲酰胺类化合物的合成及除草活性

设计合成了一系列结构新颖的嘧啶联吡唑甲酰胺类化合物5a~5o,其结构均经过1H NM R和MS分析确证。初步生物活性测试结果表明:在有效成分150 g/hm2剂量下苗后茎叶喷雾处理时,化合物(R)-N-[1-(4-氯苯基)乙基]-3-二氟甲基-1-(4,6-二甲氧基嘧啶-2-基)-1H-吡唑-4-甲酰胺(5c)、N-[1-(4-氯苯基)乙基]-1-(4,6-二甲氧基嘧啶-2-基)-N-甲基-3-三氟甲基-1H-吡唑-4-甲酰胺(5i)和N-[1-(4-氯苯基)乙基]-1-(4,6-二甲氧基嘧啶-2-基)-3-三氟甲基-1H-吡唑-4-甲酰胺(5k)对繁缕Stellaria media的抑制率高达90%以上;而同样剂量下苗前土壤喷雾处理时,化合物N-[1-(4-氯苯基)乙基]-3-二氟甲基-1-(4,6-二甲氧基嘧啶-2-基)-1H-吡唑-4-甲酰胺(5b)和5c对繁缕的抑制率达100%。该类结构化合物有望作为除草先导化合物进行开发。     

单嘧磺酯水解及在水中的光解研究

实验室条件下,利用高效液相色谱研究了单嘧磺酯水解和在水中的光解动态特性。结果表明:在pH值分别为5、7和9的缓冲溶液中,25 ℃时单嘧磺酯的水解半衰期分别为13.1、192和347 d,为易水解或较难水解,50 ℃时则分别为19.6 h和4.6、7.1 d,为易水解;其水解速率随着温度的升高而升高,温度效应系数为32.7~48.9;单嘧磺酯在酸性缓冲溶液中水解最快,在碱性条件下水解最慢,其水解活化能和活化熵与缓冲溶液的pH值呈显著正相关关系。在25 ℃、照度为3 620 lx 以及紫外强度为71.1 μW/cm2条件下,单嘧磺酯在水中的光解半衰期为4.9 h,为较易光解。     

Photolysis of organophosphorus insecticides on soil surfaces

Photolysis on soil surfaces of the organophosphorus insecticides diazinon, methidathion and profenofos was studied under artificial sunlight conditions. All three compounds were readily degraded under the conditions used. The rate of degradation decreased in the order diazinon, profenofos, methidathion and was always greater in moist than in dry soil. The same order of stability was also observed from photolysis studies in aqueous solution. The major photolysis products identified were 2-isopropyl-6-methylpyrimidin-4-ol from diazinon, 5-methoxy-3H-1,3,4-thiadiazol-2-one from methidathion and 4-bromo-2-chlorophenol and 4-bromo-2-chlorophenyl ethyl hydrogen phosphate from profenofos. The same compounds were formed in hydrolysis studies and also upon photodecomposition in aqueous solutions of diazinon and methidathion. Profenofos, however, showed a different photolytic reaction in aqueous systems, forming O-(2-chlorophenyl) O-ethyl S-propyl phosphorothioate. Soil photolysis studies together with hydrolysis experiments could be a useful quick method for obtaining early information on the chemical breakdown products which are to be expected in the soil environment.     

Light-induced transformations of tribenuron-methyl in aqueous solution

Tribenuron-methyl a sulfonylurea herbicide, readily photodegraded in aqueous solution under sunlight and UV light. The photoproducts identified were N-methyl-4-methoxy-6-methyl-1,3,5-triazine-2-amine, methyl 2-(aminosulfonyl) benzoate, o-benzoic sulfimide, N-(4-methoxy-6-methyl1,3,5-triazin-2-yl)-N-methyl urea and N-(2-carbomethoxyphenyl)-N-(4-methoxy-6-methyl-1,3,5triazin-2-yl)-N′-methyl urea. The rate of photodegradation of tribenuron-methyl in different types of water followed first-order kinetics with significant correlation coefficient, increased with increase in pH and was also dependent upon the dissolved impurities. © 1999 Society of Chemical Industry     

Degradation of the sulfonylurea herbicide LGC-42153 in flooded soil

LGC-42153, 2-fluoro-1-[3-(4,6-dimethoxypyrimidin-2-ylcarbamoylsulfamoyl)pyridin-2-yl]propyl methoxyacetate, is a new sulfonylurea herbicide for use in rice. Its breakdown and metabolism were studied in soil under flooded condition using radioactive tracers labelled at either the propyl group or the pyrimidine ring. The half-life of LGC-42153 was approximately 3.0 days. The mass balance over 120 days ranged from 94.0 to 104.2% of applied radiocarbon, and no significant amount of volatiles or [14C]carbon dioxide were observed. Solvent non-extractable radiocarbon reached 11 approximately 14% of applied radiocarbon at 120 days after treatment. The major metabolic reaction was the cleavage of the carboxyl ester bond to give 1-(4,6-dimethoxypyrimidin-2-yl)-3-[2-(1-hydroxy-2-fluoropropyl)pyridine-3-sulfonyl]urea, which underwent hydrolysis of the sulfonylurea bridge giving 2-(1-hydroxy-2-fluoro)propyl-3-pyridinesulfonamide and 4,6-dimethoxy-2-aminopyrimidine.     

棉田除草活性化合物SIOC0426生物活性初步评价

SIOC0426 属2-嘧啶氧基-N-芳基苄胺类选择性除草活性化合物。室内生物活性测定结果表明,SIOC0426具有良好的芽后早期除草活性,对棉花安全,在棉花与重要杂草马唐和反枝苋之间的选择性系数分别为 3.534 和4.299,能有效防除棉花田禾本科杂草和阔叶杂草,对莎草科杂草也有一定抑制作用,使用适期为杂草1~2叶期。田间试验表明,在有效成分90~120 g/hm2剂量范围内,对棉田主要杂草的总防效在73.1% ~87.6%之间。     

Mechanisms of dicarboximide ring opening in aqueous media: Procymidone,vinclozolin and chlozolinate

The hydrolysis kinetics of the dicarboximide fungicides procymidone, vinclozolin and chlozolinate in neutral and alkaline solutions of pH 60 to 13·7 at 25°C have been determined conjointly by ultraviolet spectrophotometry and by high performance liquid chromatography. Under alkaline conditions, the fungicides undergo attack by the hydroxide ion on a specific carbonyl group and the rate of hydrolysis increases proportionally to the hydroxide ion concentration. Procymidone gives quantitatively and irreversibly 2-(3,5-dichlorophenylcarba-moyl)-l,2-dimethylcyclopropanecarboxylate. The reaction is not subject to general base catalysis and experimental data are in agreement with a rate-determining attack by the hydroxide ion. After a rapid hydrolytic loss of the ethoxycarbonyl substituent from chlozolinate, the dicarboximide ring cleavage of the two other fungicides leads, by mechanisms which differ with respect to the type of base catalysis and the rate-determining step, to the corresponding anilides, producing as intermediates the carbamic acids, which undergo loss of carbon dioxide. The hydrolysis of vinclozolin and chlozolinate yields, respectively, N-(3,5-dichloro-phenyt)-2-hydroxy-2-methylbut-3-enanilide and N-(3,5-dichlorophenyl)-2-hydroxy-propanilide.     

Fate of chlorsulfuron in the environment. 1. Laboratory evaluations

The behaviour and fate of chlorsulfuron in aqueous and soil systems were examined in laboratory studies. Aqueous hydrolysis was pH-dependent and followed pseudo-first-order degradation kinetics at 25°C, with faster hydrolysis occurring at pH 5 (half-life 24 days) than at either pH 7 or 9 (half-lives >365 days). Degradation occurred primarily by cleavage of the sulfonylurea bridge to form the major metabolites chlorobenzenesulfonamide (2-chlorobenzenesulfonamide) and triazine amine (4-methoxy-6-methyl-1,3,5-triazin-2-amine). This route is a major degradation pathway in water and soil systems. Aqueous photolysis (corrected for hydrolysis) proceeded much more slowly (half-life 198 days) than aqueous hydrolysis and is not expected to contribute significantly to overall degradation. Hydrolysis in soil thin-layer plates exposed to light (half-life 80 days), however, progressed at a much faster rate than in dark controls (half life 130 days), which suggests that a mechanism other than direct photolysis may have been operative. An aerobic soil metabolism study (25°C) in a Keyport silt loam soil (pH 6·4, 2·8% OM) showed that degradation was rapid (half-life 20 days). Dissipation in an anaerobic sediment/water system (initial pH of water phase 6·7, final pH 7·4) progressed much more slowly (half-life >365 days) than in aerobic soil systems. Major degradation products in aerobic soil included the chlorobenzenesulfonamide and triazine amine as in the aqueous hydrolysis study. Neither of these degradation products exhibited phytotoxicity to a variety of crop and weed species in a glasshouse experiment, and both exhibited an acute toxicological profile similar to that of chlorsulfuron in a battery of standard tests. Demethylation of the 4-methoxy group on the triazine moiety and subsequent cleavage of the triazine ring is another pathway found in both aqueous solution and soils, though different bonds on the triazine amine appear to be cleaved in the two systems. Hydroxylation of the benzenesulfonamide moiety is a minor degradation pathway found in soils. Two soils amended with 0·1 and 1·0 mg kg^-1 chlorsulfuron showed slight stimulation of nitrification. The 1·0 mg kg^-1 concentration of chlorsulfuron resulted in minor stimulation and inhibition of ¹⁴C-cellulose and ¹⁴C-protein degradation, respectively, in the same soils. Batch equilibrium adsorption studies conducted on four soils showed that adsorption was low in this system (K_oc 13–54). Soil thin-layer chromatography of chlorsulfuron (R_f=0·55–0·86) and its major degradation products demonstrated that the chlorobenzenesulfonamide (R_f=0·34–0·68) had slightly less mobility and that the triazine amine (R_f=0·035–0·40) was much less mobile than chlorsulfuron. In an aged column leaching study, subsamples of a Fallsington sandy loam (pH_water 5·6, OM 1·4%) or a Flanagan silt loam (pH_water 6·4, OM 4·0%) were treated with chlorsulfuron, aged moist for 30 days in a glasshouse and then placed upon a prewet column of the same soil type prior to initiation of leaching. This treatment resulted in the retention of much more total radioactivity (including degradation products) than by a prewet column, where initiation of leaching began immediately after chlorsulfuron application, without aging (primarily chlorsulfuron parent). © 1998 SCI     

唑啉草酯的水解及光解特性

在实验室条件下,采用高效液相色谱和高效液相色谱-串联质谱研究了唑啉草酯在不同条件下的水解和光解特性。结果表明:在pH值分别为4.0、7.0和9.0的缓冲溶液中,25 ℃时唑啉草酯的半衰期分别为347、40.8和1.08 h,50 ℃时则分别为57.8、11.6和0.498 h,均为易水解;唑啉草酯在碱性条件下易水解,酸性条件下水解较慢;其水解速率随温度升高而升高,温度效应系数为2.18~6.00。在模拟太阳光氙灯辐射下,唑啉草酯在缓冲溶液中的光解速率随其pH值的升高而加快,在pH值为8.0时最短,为10.0 h;唑啉草酯在自然水体中的光解速率依次为池塘水 > 稻田水 > 河水 > 纯水,4种条件下的半衰期分别为5.17、7.79、8.56和38.5 h。唑啉草酯水解的主要产物是 M2 (8-(2,6-二乙基-4-甲基苯基)-9-羟基-1,2,4,5-四氢吡唑[1,2-d][1,4,5]噁二氮杂卓-7-酮),其降解机理主要是酯水解反应, M2 在光照条件下进一步降解,表明光解为唑啉草酯降解的一个重要途径。研究结果可为唑啉草酯在水体中的环境行为及其环境安全性评价提供参考。     

Degradation of the sulfonylurea herbicide LGC-42153 in flooded soil

LGC-42153, 2-fluoro-1-[3-(4,6-dimethoxypyrimidin-2-ylcarbamoylsulfamoyl)pyridin-2-yl] propyl methoxyacetate, is a new sulfonylurea herbicide for use in rice. Its breakdown and metabolism was studied in soil under flooded conditions using two radioactive tracer compounds labelled at either the propyl group or the pyrimidine ring. The half-life of LGC-42153 was approximately 3.0 days. The mass balance over 120 days ranged from 94.0 to 104.2% of applied radiocarbon, and no significant amount of volatiles or [14C]carbon dioxide were observed. Solvent non-extractable radiocarbon reached about 11-14% of applied radiocarbon at 120 days after treatment. The major metabolic reaction was the cleavage of the carboxyl ester bond to give 1-(4,6-dimethoxypyrimidin-2-yl)-3-[2-(1-hydroxy-2-fluoropropyl)pyridine-3-sulfonyl]urea, which underwent hydrolysis of the sulfonylurea bridge giving 2-(1-hydroxy-2-fluoro)propyl-3-pyridinesulfonamide and 4,6-dimethoxy-2-aminopyrimidine.     

Separation and identification of short-lived free radicals formed by photolysis of the pyrethroid insecticide fenvalerate

Using a spin-trap reagent 3-nitrosodurene (1,2,4,5-tetramethyl-3-nitrosobenzene), the short-lived free radicals generated by ultraviolet irradiation of fenvalerate [(RS)-α-cyano-3-phenoxybenzyl (RS)-2-(4-chlorophenyl)-3-methylbutyrate] in degassed benzene or dichloromethane, were scavenged as the more stable nitroxide radicals. These radicals were separated by high-performance liquid chromatography and identified individually by electron-spin resonance spectroscopy, as well as by gas chromatography/mass spectrometry. As a result, they were found to be the spin adduct mixtures of the 4-chloro-α-isopropylbenzyl and α-cyano-3-phenoxybenzyl radicals, which are involved in the photo-induced decarboxylation process of fenvalerate. Discrimination of the radicals was also performed by the isotope-labelling method whereby the benzylic proton in the acid moiety was deuteriated. The spin numbers of the nitroxides decreased by about five-fold when photolysis was carried out in oxygenated benzene solution. N-Benzylidene-tert-butylamine N-oxide trapped both radicals but much less efficiently. The nitroxide of the 4-chloro-α-isopropylbenzyl radical was predominant at 25°C or –40°C, but the proportion of the α-cyano-3-phenoxybenzyl nitroxide radical increased at the lower temperature.     

棉田除草剂溴嘧氯草醚的中试合成及杂质鉴定

为研究棉田除草剂溴嘧氯草醚(开发代号SIOC0426,化学名称为N-[2-氯-6-(4,6-二甲氧基-2-嘧啶氧基)苄基]-4-溴苯胺)的中试合成工艺,以2-氟-6-氯苯甲醛为起始原料,通过水解、缩合、还原和亲核取代反应在公斤级规模上合成了溴嘧氯草醚,用高效液相色谱外标法测定了原药含量,通过三维高效液相色谱-质谱联用(HPLC-DAD-MS)技术对原药中的杂质结构进行了鉴定。结果表明,反应总收率高于80%,原药含量大于98%,主要杂质为未反应完全的中间体2-[(4-溴苯氨基)甲基]-3-氯苯酚和溴嘧氯草醚Smiles重排产物。该工艺反应条件温和,反应收率高,原药含量高,"三废"排放较少,较适合工业化放大生产。     

Herbicidal efficacy and selectivity of pyribenzoxim in turfgrasses

Three field trials were conducted from 2003–2004 at Utsunomiya University, Japan, to evaluate the safety and herbicidal activity of pyribenzoxim (benzophenone O -[2,6-bis[(4,6-dimethoxy-2-pyrimidinyl)oxybenzoyl]oxime) in turfgrass. Pyribenzoxim showed a high level of safety in bentgrass ( Agrostis palustris Huds.) and zoysiagrass ( Zoysia matrella ) ≤ 300 g ai ha⁻¹ and it controlled various major grass weeds, including annual bluegrass ( Poa annua L.), large crabgrass ( Digitaria sanguinalis L.), and green foxtail ( Setaria viridis L.), and broadleaf weeds, including common dandelion ( Taraxacum officinale Weber), horseweed ( Erigeron canadensis L.), shepherd's-purse ( Capsella bursa-pastoris (L.) Medic.), common chickweed ( Stellaria media L.), common lambsquarters ( Chenopodium album L.), creeping woodsorrel ( Oxalis corniculata L.), and common dayflower ( Commelina communis L.) by fall or spring application. In comparison with bispyribac-sodium (sodium 2,6-[bis(4,6-dimethoxy-2-pyrimidin-2-yl)oxy]benzoate), pyribenzoxim showed a higher safety level in bentgrass and a stronger herbicidal activity on grass weeds; in particular, annual bluegrass and large crabgrass.     

Hydrolysis and photolysis of flumioxazin in aqueous buffer solutions

To determine the degradation rates and degradation products of the herbicide flumioxazin in aqueous buffer solutions (pH 5, 7 and 9), its hydrolysis and photolysis were investigated at 30 degrees C in the dark, and in a growth chamber fitted with fluorescent lamps simulating the UV output of sunlight. The rate of hydrolysis of flumioxazin was accelerated by increasing pH. The t(1/2) values at pH 5, 7 and 9 were 16.4, 9.1 and 0.25 h, respectively. Two degradation products were detected and their structural assignments were made on the basis of LC-MS data. Degradation product I was detected in all buffer solutions while degradation product II was detected in acidic buffer only. Both degradation products appeared to be stable to further hydrolysis. After correcting for the effects of hydrolysis, the photolytic degradation rate also increased as a function of pH and was approximately 10 times higher at pH 7 than that at pH 5, showing t(1/2) values of 4.9 and 41.5 h, respectively. Degradation products formed by photolysis were the same as those formed by hydrolysis. Flumioxazin was degraded more extensively at high pH and should degrade in surface water.     

Influence of herbicide application rate and timings for post-emergence control of Sorghum halepense (L.) Pers. maize

Field experiments were carried out in Greece from 1990 to 1992 to study the effect of application timing and rate of nicosulfuron and rimsulfuron on Sorghum halepense (L.) Pers. control and maize yield. All herbicide rates are given in terms of active ingredient (a.i.). Nicosulfuron applied at 22.5, 30.0 and 37.5 g ha^?1 to S. halepense at height 20–35 cm provided greater than 93% control 90 days after treatment, while rimsulfuron applied at 7.5,10.0 and 12.5 g ha^?1 resulted in 81–91% control. Split applications of nicosulfuron and rimsulfuron, as well as tank-mixtures of nicosulfuron+rimsulfuron, gave 91–94% control. Maize yield in all herbicide treatments was greater than that of the weed-infested control and similar to that of the hand-weeded control. S. halepense control with nicosulfuron and rimsulfuron applied to plants 20–35 cm tall was greater than that obtained with their application to plants 5–15, 10–20 or 35–60 cm tall. Rates of 10 and 20 g ha^?1 of rimsulfuron provided control of S. halepense similar to or significantly lower than that achieved with 30 and 60 g ha^?1 of nicosulfuron, respectively. Maize yield produced by all herbicide treatments applied at any time was significantly greater than that of the weed-infested control.     

丙炔氟草胺的水解及光解特性研究

为深入了解丙炔氟草胺的环境化学行为,通过室内模拟试验研究了其在不同条件下的水解和光解特性。结果表明:15℃下,初始质量浓度为2 mg/L的丙炔氟草胺在pH值为5、7和9的缓冲溶液中的水解半衰期分别为63.00、33.00和28.50 h,即其在碱性条件下水解最快;中性(pH 7)条件下,丙炔氟草胺在15、25和35℃下的水解半衰期分别为33.00、23.10和8.88 h,表明其水解受温度影响,温度越高,水解速率越快;丙炔氟草胺在河水中的水解速率高于在自来水和蒸馏水中的水解速率,3种条件下的半衰期分别为2.70、6.03和19.80 h。300 W汞灯照射下,丙炔氟草胺在碱性条件下的光解速率大于在酸性和中性条件下,半衰期分别为0.03、0.45和0.44 h;此外,丙炔氟草胺在不同有机溶剂中的光解速率顺序依次为甲醇 > 乙酸乙酯 > 正己烷 > 乙腈 > 丙酮;其在不同光源下的光解速率依次为500 W汞灯 > 300 W汞灯 > 氙灯。研究结果可为丙炔氟草胺的环境风险评价提供参考。