Penoxsulam 五氟磺草胺

五氟磺草胺

五氟磺草胺(penoxsulam)是由美国陶农科公司(Dow AgroSciences)所开发的苗后用除草剂，它是三唑并嘧啶磺酰胺除草剂，通过抑制乙酰乳酸合成酶(ALS)而起作用。2004年9月24日在美国EPA正式注册登记，2005年在美国南部稻区推广应用，2008年在中国登记，目前在我国登记的剂型为百分之二点五的油悬浮剂。

五氟磺草胺的通用名为penoxsulam，代号有DE-638、XDE-638、XR-638、DASH-001、DASH-1100、X-638177；商品名Clipper 25 OD、Cranite GR、Graniee SC、稻杰。化学名称为3-(2,2-二氟乙氧基)-N-(5,8-二甲氧基-[1,2,4]三唑并[1,5-C]嘧啶-2-基)-α,α,α-三氟甲苯基-2-磺酰胺。CA登录号219714-96-2。
原药为浅褐色固体，相对密度1.61g/mL(20℃)。熔点212℃，蒸气压2.49×10-14Pa(20℃)，9.55×10-14Pa(25℃)。溶解度(mg/L，19℃)：水5.7(pH5)、410(pH7)、1460(pH9)。在pH5-9的水中稳定。

毒性
对大鼠急性经口LD50>5000mg/kg，对兔急性经皮LD50>5000mg/kg，对大鼠急性吸入LC50(4h)>3.5mg/L，对眼睛和皮肤有极轻微刺激性。(表1)即为本剂无明显影响的亚急性毒性及急性毒性的每天摄食剂量。

3　剂型
有液剂、悬浮剂等。

使用方法
五氟磺草胺为稻田用广谱除草剂，可有效防除稗草(包括对敌稗、二氯喹啉酸及抗乙酰辅酶A羧化酶具抗性的稗草)、千金子以及一年生莎草科杂草，并对众多阔叶杂草有效，如沼生异蕊花(Heteranthera limosa)、鲤肠(Eclipta prostrata)、田菁(Sesbania exaltata)、竹节花(Commelina diffusa)、鸭舌草(Monochoria vaginalis)等。持效期长达30～60天，一次用药能基本控制全季杂草危害。同时，其亦可防除稻田中抗苄嘧磺隆杂草，且对许多阔叶及莎草科杂草与稗草等具有残留活性，为目前稻田用除草剂中杀草谱最广的品种.
五氟磺草胺为传导型除草剂，经茎叶、幼芽及根系吸收，通过木质部和韧皮部传导至分生组织，抑制植株生长，使生长点失绿，处理后7~14d顶芽变红，坏死，2~4周植株死亡；本剂为强乙酰乳酸合成酶抑制剂，药剂呈现较慢，需一定时间杂草才逐渐死亡。
五氟磺草胺适用于水稻的旱直播田、水直播田、秧田以及抛秧、插秧栽培田。用量为15~30g a.i./hm2。旱直播田于芽前或灌水后，水直播田于苗后早期应用；插秧栽培则在插秧后5~7d施药。施药方式可采用喷雾或拌土处理。
五氟磺草胺对水稻十分安全，2005年与2006年在美国对10个水稻品种于2~3叶期以70ga.i./hm2剂量喷施，结果无论是稻株高度、抽穗期及产量均无明显差异，此表明所有品种均有较强抗耐性。当超高剂量时，早期对水稻根部的生长有一定的抑制作用，但迅速恢复，不影响产量。

降解消失
五氟磺草胺能被土壤迅速吸附。在大多数稻田的土壤中淋溶性较弱。其在粘质土及含高有机质的土壤中的吸附量高于轻质土及低有机质含量的土壤。在pH>8.0的土壤中其具有加重药害的危险性。该药剂在土壤中易移行，且非长期滞留。由于该药剂的饱和蒸气压较低，故不易从水中蒸散；在灌水的稻田中，药剂的半衰期为2~13d；光解与微生物降解为五氟磺草胺的主要消失途径。它能在水中抗水解，但在浅水层经光解可迅速消失，该水溶液的光解为三种途径：磺酰胺桥裂解，三唑嘧啶及其取代基逐步降解，磺酰基光氧化。此光解产物可长期残留。在稻田土壤中，厌气微生物降解是药剂消失的重要过程，其消失速度和光解一样迅速。

价值
由上可见，五氟磺草胺由于其低毒、高效、安全而受人关注，其将在水稻应用中得到进一步发展，成为重要产品之一。
五氟磺草胺，杀草谱广，对水稻田常见的多种杂草，包括稗草、一年生莎草以及多种阔叶草均有良好的防效，而且持效期长达30～60天，一次用药能基本控制全季杂草危害。目前在我国登记的剂型为2．5%油悬浮剂）（稻杰），五氟磺草胺对水稻安全，在水稻1叶期至成熟期均可使用，对后茬也安全。对磺酰脲类除草剂已产生抗性的一些杂草，用稻杰也有较好的防效。要求产品合成工艺能适用于工业化，产品的质量达到出口的要求。

penoxsulam
Herbicide
HRAC B WSSA 2; triazolopyrimidine

NOMENCLATURE
Common name penoxsulam (BSI, pa ISO)
IUPAC name 3-(2,2-difluoroethoxy)-N-(5,8-dimethoxy[1,2,4]triazolo[1,5-c]pyrimidin-2-yl)-a,a,a-trifluorotoluene-2-sulfonamide; 2-(2,2-difluoroethoxy)-N-(5,8-dimethoxy[1,2,4]triazolo[1,5-c]pyrimidin-2-yl)-6-(trifluoromethyl)benzenesulfonamide
Chemical Abstracts name 2-(2,2-difluoroethoxy)-N-(5,8-dimethoxy[1,2,4]triazolo[1,5-c]pyrimidin-2-yl)-6-(trifluoromethyl)benzenesulfonamide
CAS RN [219714-96-2] Development codes DE-638; XDE-638; XR-638; X638177; DASH-001 (all Dow AgroSciences)

PHYSICAL CHEMISTRY
Composition Purity 98% nominal. Mol. wt. 483.4 M.f. C16H14F5N5O5S Form Off white solid with a musty odour. M.p. 212 °C V.p. 9.55 ´ 10-11 mPa (25 °C) KOW logP = -0.354 (unbuffered water, 19 °C) Henry 2.44 ´ 10-12 Pa m3 mol-1 (unbuffered water, calc.); 2.95 ´ 10-14 Pa m3 mol-1 (pH 7, calc.). S.g./density 1.61 (20 °C) Solubility In water 0.0049 (distilled), 0.00566 (pH 5), 0.408 (pH 7) 1.46 (pH 9) (all in g/l, 19 °C). In acetone 20.3, methanol 1.48, octanol 0.035, DMSO 78.4, NMP 40.3, 1,2-dichlorethane 1.99, acetonitrile 15.3 (all in g/l, 19 °C). Stability Stable to hydrolysis. Photolysis DT50 2 d. Storage stability >2 y. pKa 5.1 Other properties Not flammable or explosive

COMMERCIALISATION
History Under development by Dow AgroSciences LLC as a rice herbicide. Patents US 5828924 Manufacturers Dow AgroSciences

APPLICATIONS
Biochemistry Branched chain amino acid (leucine, isoleucine and valine) synthesis (ALS or AHAS) inhibitor. Selectivity is based on differential metabolism to inactive metabolites. Mode of action Absorbed via leaves, stems and roots. Symptoms include almost immediate growth inhibition, a chlorotic growing point with necrosis of the terminal bud, resulting in plant death in 2 to 4 weeks. Applied pre-emergence, post-emergence and water-applied. Uses Provides control of Echinochloa spp., as well as many broadleaf, sedge and aquatic weeds in rice. Penoxsulam provides residual weed control, depending on soil type and use rate. In tropical rice, application will be at 10-15 g/ha; in temperate rice, 20-50 g/ha. Primary use will be a post-emergence application in dry-seeded, water-seeded and transplanted rice. Formulation types SC; OD; GR.

MAMMALIAN TOXICOLOGY
Oral Acute oral LD50 for rats >5000 mg/kg. Skin and eye Acute percutaneous LD50 for rabbits > 5000 mg/kg; very slight, transient irritation. Inhalation LC50 for rats >3.50 mg/l (highest attainable concentration). NOEL For rats 500 mg/kg b.w. daily (maternal), 1000 mg/kg b.w. daily (embryo-foetal). Toxicity class EPA (formulation) III (GR, SC)

ECOTOXICOLOGY
Penoxsulam has low toxicity to fish, birds, terrestrial and aquatic invertebrates, with low to moderate toxicity to aquatic plants. Birds LD50 for mallard ducks >2000, bobwhite quail >2025 mg/kg b.w. Dietary LC50 (8 d) for mallard ducks >4310, bobwhite quail >4411 ppm. Fish LC50 (96 h) for common carp >101, bluegill sunfish >103, rainbow trout >102, silverside >129 mg/l. NOEC (36 d) for fathead minnow 10.2 mg/l. Daphnia EC50 (24 h and 48 h) >98.3 mg/l. Algae EC50 (120 h) for freshwater diatom >49.6, bluegreen algae 0.49 mg/l; EC50 (96 h) for freshwater green algae 0.086 mg/l. Other aquatic spp. EC50 (14 d) for Lemna gibba 0.003 mg/l. Bees LD50 (48 h, oral) for honey bees >110 mg/bee; (48 h, contact) >100 mg/bee. Worms LC50 (7 d and 14 d) >1000 mg/kg. Other beneficial spp. LR50 (glass plate test) for predatory mites 7.46 g/ha, parasitic wasp and green lacewing >40 g/ha. Extended laboratory test at 40 g/ha: predatory mite mortality 0%, effect on fecundity 8.2%; parasitic wasp mortality 0%, effect on fecundity 26%. Soil microbial NOEC >500 g/ha.

ENVIRONMENTAL FATE
Animals Rapidly excreted, with low potential to accumulate. Plants Following post-emergence foliar application to greenhouse plants, DT50 in indica rice 0.6 d, japonica rice 1.4 d, Echinochloa 4.4 d. Penoxsulam is first metabolised to the 5-hydroxy derivative, which is inactive. Soil/Environment Aqueous photolysis DT50 2 d; soil photolysis DT50 19 d. Under global water-seeded rice field conditions, DT50 (ave.) 6.5 d (4-10 d); under dry-seeded rice conditions DT50 (ave.) 14.6 d (13-16 d). In EU, under water-seeded field conditions DT50 (ave.) 5.9 d (5.6- 6.1 d).