CAS No. 141112-29-0

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Adverse Effects

ACTIVITY: Herbicide (cyclopropylisoxazole)

CAS Name: (5-cyclopropyl-4-isoxazolyl)[2-(methylsulfonyl)-4-(trifluoromethyl)phenyl]methanone



Pest Manag Sci. 2001 Feb;57(2):133-42.

Isoxaflutole: the background to its discovery and the basis of its herbicidal properties.

Pallett KE, Cramp SM, Little JP, Veerasekaran P, Crudace AJ, Slater AE.

Aventis CropScience, Ongar Research Station, Fyfield Road, Ongar, Essex CM5 0HW, UK. ken.pallett@aventis.com

This paper reviews the discovery of isoxaflutole (IFT), focusing on the chemical and physicochemical properties which contribute to the herbicidal behaviour of this new herbicide. IFT (5-cyclopropyl-1,2-isoxazol-4-yl alpha alpha alpha-trifluoro-2-mesyl-p-tolyl ketone) is a novel herbicide for pre-emergence control of a wide range of important broadleaf and grass weeds in corn and sugarcane. The first benzoyl isoxazole lead was synthesised in 1989 and IFT in 1990, and the herbicidal potential of the latter was identified in 1991. The decision to develop the molecule was taken after two years of field testing in North America. The biochemical target of IFT is 4-hydroxyphenylpyruvate dioxygenase (HPPD), inhibition of which leads to a characteristic bleaching of susceptible species. The inhibitor of HPPD is the diketonitrile derivative of IFT formed from opening of the isoxazole ring. The diketonitrile (DKN) is formed rapidly in plants following root and shoot uptake. The DKN is both xylem and phloem mobile leading to high systemicity. IFT also undergoes conversion to the DKN in the soil. The soil half-life of IFT ranges from 12 h to 3 days under laboratory conditions and is dependent on several factors such as soil type, pH and moisture. The log P of IFT is 2.19 and the water solubility is 6.2 mg litre-1, whereas the corresponding values for the DKN are 0.4 and 326 mg litre-1, respectively. These properties restrict the mobility of IFT, which is retained at the soil surface where it can be taken up by surface-germinating weed seeds. The DKN, which has a laboratory soil half-life of 20-30 days, is more mobile and is taken up by the roots. In addition to influencing the soil behaviour of IFT and DKN, the greater lipophilicity of IFT leads to greater uptake by seed, shoot and root tissues. In both plants and soil, the DKN is converted to the herbicidally inactive benzoic acid. This degradation is more rapid in maize than in susceptible weed species and this contributes to the mechanism of selectivity, together with the greater sowing depth of the crop.

Publication Types: Review; Review, Tutorial

PMID: 11455644 [PubMed - indexed for MEDLINE]


Meded Rijksuniv Gent Fak Landbouwkd Toegep Biol Wet. 2002;67(3):383-91.

Soil persistence of 4-HPPD-inhibitors in different soil types.

Maeghe L, Eelen H, Bulcke R.

Laboratory of Herbology, Faculty of Agricultural and Applied Biological Sciences, Ghent University Coupure Links 653, 9000 Gent, Belgium. ludo.maeghe@rug.ac.be

In field experiments carried out during the 1997-2001 period on four different soil types (sand, sandy loam, heavy sandy loam and clay) in Flanders (Belgium), the persistence of the three 4-HPPD inhibiting maize herbicides mesotrione (100 and 150 g ha-1), sulcotrione (300 and 450 g ha-1) and isoxaflutole (75 and 125 g ha-1) was studied. Therefore, soil samples were taken at regular intervals from application in spring and frozen. When all samples had been taken, greenhouse bioassays were set up to detect herbicide residues in the different soil types. Therefore, two extremely sensitive test plants, sugarbeet (Beta vulgaris L. spp. altissima Doell. var. saccharifera Deck.-Dill) and red clover (Trifolium pratense L.) were sown in the soil samples. Test plants were harvested after 2 (sugarbeet) and 3 (red clover) weeks and foliage fresh weight per plant was determined. This parameter was expressed relatively to the average fresh weight per plant of the plants sown in the control soil samples taken at each sampling date. The bioassays revealed several factors that influence the persistence of the herbicide tested. First, there is a remarkable influence of the experimental year due to variation in weather conditions (especially rainfall and temperature during the first weeks after spraying). Secondly, a different soil texture results in a highly different persistence: the shortest biological persistence was noticed each year in clay, followed by heavy sandy loam; the longest persistence was recorded in sandy and sandy loam soil types. Thirdly, there are important differences between the three herbicides tested: isoxaflutole (a member of the isoxazole chemical family) was shown to be less persistent than sulcotrione and mesotrione (both members of the triketone family). Remarkably, this was not the case in clay, where a longer persistence could be seen for isoxaflutole compared to sulcotrione and mesotrione. This study also revealed that applying a low rate results in a shorter persistence period compared to the higher rate. All these factors work together in a complex way which determines the persistence of the three herbicides tested.

PMID: 12696405 [PubMed - indexed for MEDLINE]


J Agric Food Chem. 2003 Jan 1;51(1):146-51.

Fate of isoxaflutole in soil under controlled conditions.

Beltran E, Fenet H, Cooper JF, Coste CM.

Laboratoire de Chimie Analytique, Faculte de Pharmacie, Universite de Montpellier I, 15 avenue Ch. Flahault, BP 14 491, France.

Isoxaflutole (IFT, 5-cyclopropyl-1,2-oxazol-4yl-alpha,alpha,alpha-trifluoro-2-mesyl-p-tolyl ketone) is a new pre-emergence proherbicide used in maize and sugarcane. Its two main derivatives are a diketonitrile derivative, 2-cyano-3-cyclopropyl-1-(2-methanesulfonyl-4-trifluoromethylphenyl)propane-1,3-dione, called DKN, and a benzoic acid derivative, 2-methanesulfonyl-4-trifluoromethylbenzoic acid, called BA. Few data are available of the factors influencing the degradation of IFT in soil, and the purpose of the present work was to determine the relative importance of, and factors affecting, the degradation of IFT in soil. Experiments were conducted on five soils with distinct physicochemical characteristics, at different temperatures and moisture contents in biotic and abiotic conditions. The isomerization of IFT to DKN is rapid, increasing with higher moisture contents and higher temperatures. It depends strongly on pH and is governed by chemical processes. The degradation of DKN to BA appeared to be essentially due to the biological activity of the soil.

PMID: 12502399 [PubMed - indexed for MEDLINE]


Meded Rijksuniv Gent Fak Landbouwkd Toegep Biol Wet. 2001;66(2b):723-9.

Fate of the herbicide isoxaflutole in the soil of corn fields.

Rouchaud J, Neus O, Eelen H, Bulcke R.

Laboratory of Phytopharmacy, Universite Catholique de Louvain 3, Place Croix du Sud, SCI. 15 D, 1348 Louvain-la-Neuve, Belgium.

The herbicide isoxaflutole 1 (5-cyclopropyl-4-isoxazolyl)[2- (methylsulfonyl)-4-(trifluoro-methyl)phenyl]-methanone) was applied pre-emergence at the rate of 125 g ha-1 on corn fields located in three sites different as to their soil texture and composition. In the 0-10 cm surface soil layer, the isoxaflutole soil half-life (soil dissipation kinetics of second order) was 9 days in sandy loam (Melle), 15 days in clay loam (Zevekote) and 18 days in loamy sand (Zingem) soil. The sum of the concentrations of isoxaflutole 1 and of its herbicide active metabolite diketonitrile 2 (2-cyano-3-cyclopropyl-1-(2-methylsulfonyl-4- trifluoromethylphenyl)propane-1,3-dione) had a soil half-life (dissipation kinetics of first order) of 45 days in sandy loam, and 63 days in the clay loam and loam sand soils. The soil metabolism of isoxaflutole thus generated, in the soil of field corn crops, a metabolite, the diketonitrile 2, which had an herbicide activity as high as the one of the parent isoxaflutole, and which much extended the herbicide protection given by isoxaflutole. At the crop harvest, isoxaflutole, the diketonitrile 2 and the acid 3 (2-methylsulfonyl-4-trifluoromethylbenzoic acid) were no more detected in soil. During the corn crops, isoxaflutole, and its metabolites diketonitrile 2 and acid 3 were never detected in the 10-15 et 15-20 cm surface soil layers, indicating the very low mobility of these compounds in soil.

PMID: 12425096 [PubMed - indexed for MEDLINE]


J Agric Food Chem. 2003 Dec 31;51(27):8011-4.
Degradation of isoxaflutole (balance) herbicide by hypochlorite in tap water.

Lin CH, Lerch RN, Garrett HE, George MF.

Center for Agroforestry, School of Natural Resources, University of Missouri-Columbia, Columbia, Missouri 65211, USA. Linchu@missouri.edu

Chlorine has been widely employed for the disinfection of drinking water. Additionally, it has the capacity to oxidize many organic compounds in water. Isoxaflutole (Balance; IXF) belongs to a new class of isoxazole herbicides. Isoxaflutole has a very short soil half-life and rapidly degrades to a stable and phytotoxic metabolite, diketonitrile (DKN). Further degradation of DKN produces a nonbiologically active benzoic acid (BA) metabolite. In experiments using high-performance liquid chromatography-UV spectroscopy (HPLC-UV) and HPLC tandem mass spectrometry (HPLC-MS/MS), DKN was found to rapidly react with hypochlorite in tap water, yielding the BA metabolite as the major end product. One milligram per liter (19 microM) of hypochlorite residue in tap water was able to completely oxidize up to 1600 microg/L (4.45 micromol/L) of DKN. In tap water, the disappearance of IXF was much more rapid than in DI water. As soon as the IXF is hydrolyzed to DKN, the DKN quickly reacts with the OCl(-) to form nonphytotoxic BA. As a result, the herbicide solutions prepared with tap water at 500 microg/L will no longer possess any herbicidal activity after 48 h of storage. However, in agronomic settings, highly concentrated tank solutions (600-800 mg/L) may be prepared with tap water since the conversion of IXF to BA would represent <5% of the herbicide; therefore, any impact on the herbicide efficacy would be negligible. Results of this study show that current chlorination disinfection protocols in municipal water systems would completely eliminate the phytotoxic form of this new herbicide, DKN, from drinking water supplies; yet, farmers can use chlorinated tap water without significant loss of efficacy.

PMID: 14690388 [PubMed - indexed for MEDLINE]


J Agric Food Chem. 2002 Sep 25;50(20):5626-33.

Effects of moisture, temperature, and biological activity on the degradation of isoxaflutole in soil.

Taylor-Lovell S, Sims GK, Wax LM.

Department of Crop Sciences, University of Illinois, Urbana 61801, USA.

The effects of several environmental factors on the dissipation, transformation, and mineralization of isoxaflutole were investigated in laboratory incubations. In the soil, isoxaflutole hydrolyzed to a diketonitrile derivative, which is the active form of the herbicide. The diketonitrile was then metabolized to an inactive benzoic acid derivative and later into two unknown products, which were found only in small quantities. Degradation of isoxaflutole was faster in soil maintained at -100 or -1500 kPa compared to that in air-dry soil. At 25 degrees C, the half-lives for isoxaflutole were 9.6, 2.4, and 1.5 days in air-dry, -1500 kPa, and -100 kPa moisture regimes, respectively. A simple Arrhenius expression described the response of isoxaflutole transformation (mineralization and transformation) to temperature in the range of 5 to 35 degrees C. An activation energy value (E(a)) of 67 kJ/mol for isoxaflutole suggested the transformation of the herbicide to the diketonitrile derivative was primarily a chemical reaction. Moreover, biological activity had little effect on the hydrolysis of isoxaflutole, with half-lives of 1.8 and 1.4 days in sterile and nonsterile soil, respectively. However, the transformation of diketonitrile to benzoic acid and the production of the unknown products were greatly reduced in the sterile soil, suggesting one or more biologically mediated processes.

PMID: 12236689 [PubMed - indexed for MEDLINE]


Arch Environ Contam Toxicol. 2002 Apr;42(3):280-5.

Soil metabolism of isoxaflutole in corn.

Rouchaud J, Neus O, Eelen H, Bulcke R.

Laboratory of Phytopharmacy, Catholic University of Louvain, 3, Place Croix du Sud, SCI. 15D, 1348 Louvain-la-Neuve, Belgium.

The herbicide isoxaflutole 1 (5-cyclopropyl-4-isoxazolyl)[2-(methylsulfonyl)-4-(trifluoromethyl)phenyl]-methanone) has been applied preemergence at the rate of 125 g ha(-1) on corn crops grown on fields located in regions different as to their soil textures. Its metabolite diketonitrile 2 (2-cyano-3-cyclopropyl-1-(2-methylsulfonyl-4-trifluoromethylphenyl)propane-1,3-dione)-which is the herbicide's active compound-and its nonherbicide metabolite 3 (2-methylsulfonyl-4-trifluoromethylbenzoic acid) were measured in the 0-10 cm surface soil layer of the corn crops after the treatment and until the harvest. At the opposite of what occurred in plant shoots, the transformation of isoxaflutole 1 into diketonitrile 2 was not immediate in soil. In the 0-10 cm surface soil layer, this transformation occurred progressively according to an apparent second-order kinetics, and the soil half-lives of isoxaflutole 1 self were comprised between 9 and 18 days. The adsorption of isoxaflutole 1 onto the solid phase of the soil and its organic matter should explain the stabilization effect of soil, increased by the application of fresh organic fertilizer. The sum of the concentrations of isoxaflutole 1 and diketonitrile 2 disappeared in the 0-10 cm surface soil layer according to an apparent first-order kinetics, and the soil half-lives of this sum were comprised between 45 and 65 days. The sum of the concentrations of isoxaflutole 1 and of its metabolites diketonitrile 2 and acid 3 did not account for the amount of isoxaflutole 1 applied. The discrepancy increased with the delay after the application, showing that the acid 3 was further metabolized in soil into common nontoxic products, and ultimately into CO2. The conjunction of the adsorption of isoxaflutole and its metabolites (which reduced their mobilities) onto the soil and its organic matter, and their further metabolism should explain why isoxaflutole and its metabolites were not detected in the 10-15 and 15-20 cm surface soil layers during the crops.

PMID: 11910455 [PubMed - indexed for MEDLINE]

From Science Direct

Environmental Pollution; Volume 108, Issue 2 , May 2000, Pages 183-190

Sorption and desorption of the diketonitrile metabolite of isoxaflutole in soils

S. Mitra, P.C. Bhowmik and B. Xing

Department of Plant and Soil Sciences, Stockbridge Hall, University of Massachusetts, Amherst, MA 01003, USA

Isoxaflutole is a new pre-emergence corn herbicide that undergoes rapid conversion to a diketonitrile derivative (DKN) in soils. Sorption–desorption studies were conducted in five different soils varying in physical and chemical properties. A batch equilibration technique was used with total initial aqueous solution concentrations of DKN at 0.25, 0.75, 2.0, 8.0, 25, 75, 150, and 250 mg l-1. After the sorption process, two subsequent desorptions were conducted with an equilibration period of 7 days. A high correlation existed between the desorption coefficient, KFd and the organic matter content of soils (r2=0.844 for the first desorption and r2=0.861 for the second desorption), while the clay content did not greatly influence the desorption of DKN. Although the sorption of DKN was generally reversible, a sorption–desorption hysteresis was apparent in all soils. The site energy distribution curves emphasized the fact that DKN binds tightly to soils with higher organic matter content and greater proportion of DKN was retained by those soils

From Toxnet at Toxline

WEED SCIENCE; 46 (4). 1998. 397-402.

Optimizing foliar activity of isoxaflutole on giant foxtail (Setaria faberi) with various adjuvants.


Crop Sci. Dep., Univ Ill., Urbana, IL 61801, USA.

BIOSIS COPYRIGHT: BIOL ABS. Greenhouse, laboratory, and field studies were conducted to evaluate the potential of nonionic surfactant (NIS), crop oil concentrate (COC), methylated seed oil (MSO), and 28% urea ammonium nitrate (UAN) to enhance whole plant efficacy, absorption, and spray retention of foliar applications of isoxaflutole to giant foxtail. In greenhouse studies, isoxaflutole at 10 g ai ha-1 reduced giant foxtail growth 5%, whereas the addition of a spray adjuvant reduced giant foxtail growth at least 75%. The addition of UAN improved giant foxtail growth reduction when used in combination with isoxaflutole plus NIS. Isoxaflutole spray retention on the leaf surface was increased with an adjuvant and a further increase was observed with the addition of UAN. Isoxaflutole applied with NIS, COC, and MSO resulted in 42, 60, and 91% 14C absorption, respectively, compared to 21% absorption from isoxaflutole applied alone 24 h after treatment (HAT). Increased 14C absorption and entry into the c [abstract truncated]

Agronomy-Weed Control
Pest Control

CAS Registry Numbers:
141112-29-0 - Isoxaflutole
15978-77-5 - Nitric acid ammonium salt, mixt. with urea

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