Phototransformation of napropamide [N,N-diethyl-2-(1-naphthyloxy)propionamide] in aqueous solution: influence on the toxicity of solutions

The main photoproducts formed in an aqueous solution of napropamide irradiated in UV light are N,N-diethyl-2-(1-hydroxynaphthalen-2-yl)propionamide, N,N-diethyl-2-(4-hydroxynaphthalen-1-yl)propionamide and 1-naphthol. These account for c.60%, 15% and 10% of napropamide converted respectively. No influence of the irradiation wavelength or of oxygen was observed. The same products were obtained by irradiation of methanolic solutions. The three identified products result from the cleavage of naphthoxy–carbon bond. The first two products imply a photo-Fries rearrangement. The influence of irradiation on the toxicity of the solutions was studied by the Microtox™ test. The significant increase observed may be attributed partly to the formation of 1-naphthol. © 1998 Society of Chemical Industry     

Absence of 3-(2,4-dichlorophenoxy)propionic acid in plants treated with 2,4-dichlorophenoxyacetic acid‡

Experiments were conducted to establish if the formation of 2.4-dichlorophenol (DCP) from 2.4-dichlorophenoxyacetic acid (2,4-D) in plants proceeds via 3-(2,4-dichtorophenoxy) propionic acid (2,4-DP) as an intermediate. Soybean (Glycine max (L.) Merr.), kidney bean (Phaseolus vtitgaris L.), pea (Pisum. sativum L.), smooth bromegrass (Bromus inermis Leyss.), wild oat (Avena fatua L.), yellow foxtail (Setaria glauca(L.) Beauv.), barley (Hordeum vulgare L.), timothy (Phleum pratense L.). and orchardgrass (Dactylis glomerata L.) were treated with equal weights of 2,4-D and 2,4-DP. After 3 days, all plants contained DCP; however, amounts were larger in plants treated with 2.4-DP than in those treated with 2,4-D. The 2.4-DP was absorbed from the leaf surface more efficiently than 2,4-D. No evidence was found for formation of 2,4-DP from 2,4-D in any of the plant species studied. L'absence de l'acide3-(2,4 dichlorophénoxy) propionique dans les plantes traitées avec I'acide 2,4-dichlorophénoxyacétique Des experiences ont été effectuées pour rechercher si la formation de 2,4-dichlorophénoI (DCP) dans les plantes, à partir de l'acide 2.4-dichlorophénoxy acétique (2,4-D) se produit par l'intermêdiaire de l'acide 3-(2,4-dichlorophenoxy) propionique. Le soja (Glycine max(L.) Merr.). le haricot (Phaseolus vuigaris L.), Ic pois (Pisum sativum L.), le brome (Bromus inermis Leyss.), la folle avoine (Avena fatua L.), la sétaire (Setaria glauca(L.) Beauv.). I'orge (Hordeum vulgare L.), la fléole (Phleum pratense L.) et le dactyle (Dactylis ghmerata L.) ont été traités par des poids égaux de 2.4-D et de 2,4-DP. Trois jours aprés, les plantes contenaient du DCP; toutefois, les quantités trouviés furent plus importantes dans les plantes traitées avec le 2,4-DP que dans celles traitées avec le 2,4-D. Le 2,4-DP a été absorbéà partir de la surface foliaire plus efficacement que le 2,4-D. La formation du 2,4-DP à partir du 2,4-D n'a pu être prouvée dans aucune des plantes étudiécs. Die Abwesenheit von 3-(2,4′Dichlorphenaxy)-propionsäure irt mil 2,4-Dichlorphenoxytesäure behandelten Pflanzen Es wurden Versuche durchgeführt um herauszufinden. ob die Bildung von 2,4-Dichlorphenol (DCP) aus 2.4-Dichlor-phenoxyessigsäure (2,4-D) in Pflanzen über 3-(2,4-Dichlor-phenoxy)-propionsaure (2,4-DP) als Zwischcnprodukt ver-läufl. Sojabohnen (Glycine max(L.) Merr.), Gartenbohnen (Phaseolus vutgaris L.), Erbsen (Pisum sativum L.), Wehrlose Trcspe (Bromus inermis Leyss.), Flughafer (Avena fama L.), Gelbe Borsienhirse (Setaria glauca(L.) Beauv.), Gerste (Hordetim vidgarc L.), Wiesenlieschgras (Phleum pratense L.) und Knaulgras (Dactylis ghmerata L.) wurden mit gleichen Mengen an 2,4-D und 2,4-DP behandelt. Nach drei Tagen enthielten alle PHanzen DCP; aber die Menge an DCP war in den mit 2,4-DP behandelten Pflanzen grosser als in den mit 2,4-D behandelten. 2,4-DP wurde von der Blatt-oberflache besser absorbiert als 2.4-D. In keiner der untersuchten Pflanzenarten konnte ein Hinweis für die Bildung von 2,4-DP aus 2,4-D gefunden werden.     

Investigation of acute toxicity of (2,4-dichlorophenoxy)acetic acid (2,4-D) herbicide on crayfish (Astacus leptodactylus Esch. 1823)

The acute 96 h LC₅₀ of (2,4-dichlorophenoxy)acetic acid (2,4-D), a widely used agricultural herbicide, was determined on crayfish (Astacus leptodactylus Esch. 1823). Crayfish of 23.5 ± 1.49 g mean weight and 9.6 ± 0.21 cm mean length were selected for the bioassay experiments. The experiments were repeated three times, in 10 L tap water. The data obtained were statistically evaluated by the use of the E.P.A computer program based on Finney’s probit analysis method and the 96 h LC₅₀ value for crayfish was calculated to be 32.6 mg/L in a static bioassay test system. 95% lower and upper confidence limits for the LC₅₀ were 15.10-327.16. In conclusion, 2,4-D is highly toxic to crayfish, a non-target organism in the ecosystem. Water temperature was 23 ± 1 °C. Behavioral changes of crayfish were recorded for all herbicide concentrations.     

Direct and induced phototransformation of mecoprop [2‐(4‐chloro‐2‐methylphenoxy)propionic acid] in aqueous solution

Mecoprop was irradiated under various conditions of pH, oxygenation and wavelengths in order to study the reactions involved in the phototransformation. Four main photoproducts were identified: 2‐(4‐hydroxy‐2‐methylphenoxy)propionic acid ( I ), o‐cresol ( II ), 2‐(5‐chloro‐2‐hydroxy‐3‐methylphenyl)propionic acid ( III ) and 4‐chloro‐o‐cresol ( IV ). When the anionic form of mecoprop was irradiated between 254 nm and 310 nm (UV‐C or UV‐B), I was the main photoproduct. At 254 nm its formation initially accounted for more than 80% of the transformation. It has not previously been reported in the literature. The reaction results from a heterolytic photohydrolysis. Product II accounted for only a low percentage of the transformation. The stoichiometry was different with the molecular form: the main photoproduct, III , resulted from a rearrangement after a homolytic scission. Products I, II and IV were also formed as minor photoproducts. Some other minor photoproducts were also identified. In contrast, IV was the main photoproduct under sunlight irradiation or when solutions were irradiated in near‐UV light (UV‐A). This wavelength effect is attributed to the involvement of an induced phototransformation; IV is also the main photoproduct when the phototransformation is induced by Fe( III ) perchlorate or nitrite ions. In usual environmental conditions the excitation of the molecular form is negligible and the phototransformation is mainly due to induced photoreactions. © 2000 Society of Chemical Industry     

Physiological effects of methyl 2-[4(2,4-dichlorophenoxy)phenoxy] propanoate on oat,wild oat,and wheat

Methyl 2-[4-(2,4-dichlorophenoxy)phenoxy]propanoate (dichlofop-methyl) is a selective herbicide for wild oat (Avena fatua L.) control in wheat (Triticum aestivum L.). Dichlofop-methyl inhibited IAA-stimulated elongation of oat and wheat coleoptile segments by 51 and 13%, respectively, at 10 μM concentrations. Dichlofop-methyl alone had no auxin activity at concentrations of 0.1, 1.0, and 10 μM. The inhibitory effect of dichlofop-methyl was overcome partially by increasing the IAA concentration or by application of 3,6-dichloro-o-anisic acid (dicamba), a herbicide with weak auxin activity. The de-esterified free acid metabolite, 2-[4-(2,4-dichlorophenoxy)phenoxy]-propionic acid (dichlofop), at 10 μM inhibited auxin-stimulated oat coleoptile elongation by 23%, but it did not affect wheat coleoptile elongation at the same concentration. Both dichlofop-methyl and dichlofop inhibited root growth in excised shoots and seedlings of wild oat but had no effect on wheat. Dichlofop was a more effective inhibitor of root growth than dichlofop-methyl. The results suggest that dichlofop-methyl functions as a strong auxin antagonist, while the metabolite, dichlofop, inhibits root growth and development by another mechanism. The herbicidal effect of dichlofop-methyl may be the net effect of two biologically active forms of the compound each with a different mode of action acting at different sites within a susceptible plant.     

Kinetics of heterogeneous photocatalytic decomposition of 2,4-dichlorophenoxyacetic acid over titanium dioxide and zinc oxide in aqueous solution

The photocatalytic transformation of 2,4-D in aqueous solution containing a suspension of titanium dioxide or zinc oxide leads to the formation of intermediates which are totally mineralised to carbon dioxide and hydrogen chloride (2,4-dichlorophenol and chlorohydroquinone are the major intermediates). The products at the initial stage of the reaction were 2,4-dichlorophenol (2,4-DCP), chlorohydroquinone, 4-chloropyrocatechol, 2,4-dichloropyrocatechol and 1,4-chlorobenzoquinone. The initial rate of photodegradation was studied as a function of the initial concentration of reactants by the linearised form of the Langmuir–Hinshelwood equation, by which rate constants k and equilibrium adsorption constants K were evaluated. These constants were calculated at different temperatures between 25 and 60°C. The photodegradation rate increased with increase of pH. The photocatalytic transformation of 2,4-D over titanium dioxide or zinc oxide in solution containing hydrogen peroxide was studied. The latter accelerated the reaction rate of 2,4-D significantly. It was found that chloride or bicarbonate ions slowed down the photodegradation rate of 2,4-D by scavenging hydroxyl radicals. Partial inhibition by ethanol is attributed to scavenging of the OH radicals involved in the first step of the reaction. © 1998 Society of Chemical Industry     

Preparation of (R)-2-(4-hydroxyphenoxy) propionic acid by biotransformation

With Beauveria bassiana Lu 700 as biocatalyst an ecologically beneficial process has been developed for the production of (R)-2-(4-hydroxyphenoxy) propionic acid. The fungal strain used in this process, B. bassiana Lu 700, is also a very suitable catalyst for the selective monohydroxylation of other aromatic carboxylic acids.     

Phototransformation of metoxuron [3‐(3‐chloro‐4‐methoxyphenyl)‐1,1‐dimethylurea] in aqueous solution

UV irradiation of metoxuron in aerated aqueous solution at 254 nm or between 300 and 450 nm led initially to an almost specific photohydrolysis of the C–Cl bond, resulting in the formation of 3‐(3‐hydroxy‐4‐methoxyphenyl)‐1,1‐dimethylurea (MX3) and hydrogen chloride. The quantum yield was determined to be 0.020 (±0.005) in solutions irradiated at 254 nm. Five minor photoproducts were also identified, in particular the dihydroxydimethoxybiphenyl derivatives resulting from the phototransformation of MX3. Irradiation increased the toxicity of an aqueous solution of metoxuron to the marine bacterium Vibrio fischeri. © 2001 Society of Chemical Industry     

Metabolism of [14C]-2,4-dichlorophenol in edible plants

Several 2,4-dichlorophenoxyacetic acid (2,4-D)-sensitive plants have been modified by genetic engineering with tfdA gene to acquire 2,4-D tolerance. The expression product of this gene degrades 2,4-D to 2,4-dichlorophenol (DCP), which is less phytotoxic but could cause a problem of food safety. After a comparison of 2,4-D and DCP metabolism in transgenic 2,4-D-tolerant and wild cotton (Gossypium hirsutum L.), a direct study of DCP metabolism in edible plants was performed. After petiolar uptake of a [U-phenyl-(14)C]-DCP solution followed by a 48 h water chase, aqueous extracts were analysed by high-performance liquid chromatography. Metabolites were thereafter isolated and their structural identities were determined by enzymatic and chemical hydrolyses and mass spectrometry analyses. The metabolic fate of DCP was equivalent to 2,4-D metabolism in transgenic 2,4-D-tolerant cotton. In addition, DCP metabolism was similar in transgenic and wild cotton. The major terminal metabolites were DCP-saccharide conjugates in all species, essentially DCP-(6-O-malonyl)-glucoside or its precursor DCP-glucose. The significance of this metabolic pathway with regard to food safety is discussed.     

1-[2-苄氧基-2-(2,4-二氟苯基)乙基]-1H-1,2,4-三唑衍生物的合成及杀菌活性

以抗真菌药物益康唑为先导化合物,设计合成了17个1-((2-取代苄基) 氧基)-2-(2,4-二氟苯基) 乙基)-1H-1,2,4-三唑类目标化合物,其中14个为首次报道,其结构均经 1H NMR、13C NMR和HRMS确认。采用菌丝生长速率法测定了目标化合物对7种植物病原菌的抑制效果,并对毒力较高的化合物进行了其对水稻纹枯病和小麦条锈病的盆栽和田间药效试验,而且测定了其对水稻纹枯病菌麦角甾醇生物合成的抑制作用。结果表明:大多数目标化合物对测试病原菌菌丝生长有较强的抑制作用,尤其对水稻纹枯病菌和番茄早疫病菌的抑制作用最好,其中对水稻纹枯病菌的EC₅₀值均低于3 μmol/L,明显高于对照药剂苯醚甲环唑和益康唑;化合物 4a 、 4b 、 4c 、 4g 、 4i 和 4l 对番茄早疫病菌的EC₅₀值均低于10 μmol/L。在浓度为250 μmol/L时,化合物 4b 和 4i 对小麦条锈病的盆栽防效均超过70%,在有效剂量为240 g/hm2时,化合物 4b 对小麦条锈病的田间防效达到81.93%。而且,化合物 4b 和 4i 在100 μmol/L时可有效抑制水稻纹枯病菌麦角甾醇的生物合成,抑制效果在80%左右。     

吡啶衍生物研究(V):2-[(2-氯吡啶)-4-基]-5-芳胺基-1,3,4-噻二唑的合成及杀菌活性

合成了一系列 2 - [(2 -氯吡啶 ) - 4 -基 ]- 5-芳胺基 - 1,3,4 -噻二唑类化合物 ,其结构经元素分析、1H NMR、和 13 C NMR确认。初步生物活性测定表明 ,合成化合物对某些真菌生长表现出较好的抑制活性 ,如 I- 0 2在 50 0 μMg· m L-1剂量下对水稻纹枯病菌生长的抑制率达87.5%。     

吡啶衍生物研究(V):2-[(2-氯吡啶)-4-基]-5-芳胺基-1,3,4-噻二唑的合成及杀菌活性

合成了一系列 2 - [(2 -氯吡啶 ) - 4 -基 ]- 5-芳胺基 - 1,3,4 -噻二唑类化合物 ,其结构经元素分析、1H NMR、和 13 C NMR确认。初步生物活性测定表明 ,合成化合物对某些真菌生长表现出较好的抑制活性 ,如 I- 0 2在 50 0 μg· m L-1剂量下对水稻纹枯病菌生长的抑制率达87.5%。     

N-｛5-[1-(2,4-二氯苯氧)乙基]-1,3,4-噻二唑-2-基｝ -N''-芳酰基硫脲的合成及其生物活性

通过2-氨基-5- -1,3,4-噻二唑与芳酰基异硫氰酸酯反应,合成了12 个新的芳酰基硫脲,采用核磁共振氢谱、红外光谱和元素分析确证了它们的结构。初步的生物活性测定试验表明,部分化合物具有良好的植物生长调节活性,其中化合物 2c、2j 具有较好的生长素活性,其促进率分别为26.6%与26.9%,但不及对照β-吲哚乙酸。     

3-[2-(4-氯-苯基)-1-(3,3-二甲基-氧代-丁基)-乙烯基]-2-氰基亚胺-1,3-噻唑的合成研究

本文研究了3-[2-(4-氯-苯基)-1-(3,3-二甲基-氧代-丁基)-乙烯基]-2-氰基亚胺-1,3-噻唑的合成方法,对反应的各个步骤中的投料摩尔比、溶剂、温度和催化剂进行了对比,优化了反应步骤,总结出了产率较高的合成路径。设计合成了未见报道的新型噻唑衍生物类化合物。其结构经红外光谱、氢核磁共振和气质联用谱图确认,总收率为37.3%。该合成技术降低了成本,减轻了对环境的污染,具有很好的发展前景和市场竞争力。     

氰氟草酯及其活性代谢物在水溶液中的光化学降解研究

以紫外光(254 nm)为光源,研究了氰氟草酯及其活性代谢产物氰氟草酸(ACID)在不同水溶液中的光化学降解。结果表明:氰氟草酯及ACID在pH 5.0的缓冲溶液和pH 6.8的去离子水中易发生光解,丙酮的存在对氰氟草酯及ACID的光解有延缓作用。通过GC-MS和HPLC鉴定了氰氟草酯及ACID光解后的部分产物,从而推测了其可能的光解途径。     

N-取代苯基-1-(2,4-二氟苯基)-2-(1H-1,2,4-三唑-1-基)乙基氨基甲酸酯的合成及生物活性

为了寻找高活性的三唑类苯基氨基甲酸酯衍生物,以 1,2,4-三氮唑、2-氯-2,4-二氟苯乙酮为原料,采用活性亚结构拼接的策略,设计并合成了18个未见文献报道的N-取代苯基-1-(2,4-二氟苯基)-2-(1H-1,2,4-三唑-1-基)乙基氨基甲酸酯衍生物 6a ~ 6r 。其结构均通过 1H NMR、13C NMR和高分辨质谱（HRMS）的确证。抑菌活性测定结果显示:在100 μmol/L下,化合物 6m 对6种供试真菌具有良好的抑制作用,抑制率均达到50%以上。化合物 6p 对油菜菌核病菌Sclerotinia sclerotiorum的EC₅₀值为7.1 μmol/L,抑菌活性高于对照药剂烯唑醇（EC₅₀值9.1 μmol/L）。杀螨活性测定结果显示,在150 μmol/L时,化合物 6h 、 6k 和 6o 在48 h时对朱砂叶螨Tetranychus cinnabarinus的致死率分别为67.7%、74.9%和57.5%,杀螨活性低于对照药剂阿维菌素B1a(致死率100%)。本研究所合成的化合物 6o 兼具一定杀菌和杀螨活性,可为新型三唑类杀菌杀螨化合物的设计与研究提供参考。     

Increased intensity of tert-butoxyl radical emission in 4-chloro-2-methylphenoxyacetic acid (MCPA) synthesis

The important herbicide, 2-methyl-4-chlorophenoxyacetic acid (MCPA) was synthesized by the chlorination of 2-methylphenoxyacetic acid with tert-butyl hypochlorite in the presence of methyl N,N-dimethylglycinate as a catalyst, giving a high yield and regioselectivity. The reaction was investigated using the spin-trapping technique in electron paramagnetic resonance measurement conditions, with nitrosodurene as a spin trap. Increased intensity emission of the tert-butoxyl radical (2.9 times in relation to the starting level) was observed after the catalyst had been introduced into the reaction mixture, indicating a free radical mechanism for the reaction. © 1999 Society of Chemical Industry