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D. degreein 3011 Chemistry Major profe // 0 Date 0-7639 INTERACTIONS OF BUTHIDAZOLE (3-{5-(1,1-DIMETHYLETHYL)-l,3,4-THIADIAZOL-2-YL} -4-HYDROXY-l-METHYL-2-IMIDAZOLIDIONE) WITH CLAY MINERALS AND SOILS BY Song-Wu Li A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Crop and Soil Sciences 1980 1w a” ' w/ ABSTRACT INTERACTIONS OF BUTHIDAZOLE (3-{5-(1,1-DIMETHYLETHYL)-l,3,4-THIADIAZOL-2-YL} -4-HYDROXY-l-METHYL-2-IMIDAZOLIDINONE) WITH CLAY MINERALS AND SOILS BY Song-Wu Li The newly developed herbicide, buthidazole, which contains heterocyclic nitrogen and sulfur, has been studied with respect to behavior with soils and homoionic clay minerals. Results show that it can enter into the interlamellar space of swelling clays, in particular smectite. Isothermic adsorption studies indicate that Cu(II)-smectite adsorbed more buthidazole than Cu(II)- kaolinite. The Cu(II)-clay adsorption obeys the Langmuir model. The effect of exchangeable cations on adsorption is not significant in soils of high organic matter content, i.e. Houghton muck. Destruction of organic matter in Brookston loam decreases the amount of adsorption at 50°C, but not at 21°C. Infrared spectroscopic studies Shows the coordination of buthidazole and Cu(II) through Z>C=0...Cu interaction. The ligand to metal ratio is Song-Wu Li 1 to 1. Other transition metals, Ni(II), CO(II), and Fe(II) are also able to form somewhat stable complexes by the same mechanism. Protonation of buthidazole occurs in Al(III)- and H+-Smectite. No significant chemical interaction between buthidazole and soil organic matter was detected. Catalytic alteration of buthidazole occurred in the H+- and Cu(II)-smectite system but did not take place in the Ca(II)-smectite system. The herbicide is labile to UV-light irradiation at 254 nm but not at 366 nm. The photoconversion is a first order reaction. The photolytic product(s) include the -N=C=O structure. Copper(II) ions which form complexes can retard photolysis of buthidazole in UV-light, while the Ca(II) ions, which are unable to form complexes, cannot. Adsorbed buthidazole did not seem to have decreased bioactivity in either clays or in organic soils. ACKNOWLEDGEMENTS I would like to thank the National Science Council, The Republic of China, for my first two years of finan- cial support to study at Michigan State University. I am also grateful to many individuals for their kind help. First, I would like to thank Dr. Max M. Mortland, my major advisor, for his motivating guidance and patient advice. I am also very grateful to Dr. Thomas S. C. Wang, Former Advisor of Taiwan Sugar Company, for his kind regard and strong recommendation before his retirement. Appreciation is also extended to Drs. Boyd G. Ellis, James M. Tiedje, and Thomas J. Pinnavaia, the committee of my program, for their effective sug- gestions during this study. I would also like to thank Dr. S. C. Shih, Director of Taiwan Sugar Research ‘Institute, and Dr. C. C. Wang, Head of the Department of Plant Nutrition, for their kind help before and during my leave, especially for the extension of my study. I am pleased to dedicate this thesis to my Mother, Feng-Shiu, who devoted almost all her life to our family and passed away during this study. It is also my great pleasure to mention the constant encouragement from my ii wife, Hsin-Hui. Without her, this work could hardly have been completed. iii TABLE OF CONTENTS LIST OF TABLES O O O O C O O O O O C 0 LIST OF FIGURES . . . . . . . . . . . INTRODUCTION 0 O O O O O O O O O O O 0 LITERATURE REVIEW . . . . . . . . . . MATERIALS AND METHODS . . . . . . . . Preparation of Homoionic Clays Preparation of Soil Samples . . Properties of Buthidazole . . . Intercalation of Buthidazole in Smectite . . . . . . . . . . Adsorption of Buthidazole on Clay Minerals and Soils . . . . . . Infrared Spectroscopic Study . . Photolysis of Buthidazole . . . Bioactivity Study of Buthidazole RESULTS AND DISCUSSION . . . . . . . . I. II. Crystal Structure of Buthidazole Adsorption Phenomenon of Buthidazole on Clay Minerals and Soils . . A. Swelling Properties of Clays B. Isothermic Adsorption of Buthidazole . . . . . . . 1. Adsorption Models . . . 2. Isothermic Adsorption of Buthidazole on Clay Minerals . . . . . . . 3. Isothermic Adsorption of Buthidazole on Soils . 4. Thermodynamic Considerations from the Isothermic Adsorption of Buthidazole . . . . 5. Relationship of Laboratory Studies to Field Application . . . . . iv Page vi vii ll 11 12 12 15 21 22 23 24 27 27 27 27 30 30 32 50 50 6O C. Complex Formation of Buthidazole 1. Coordination Complexes of Buthidazole with Transition Metals 2. Interaction between Other Cations and Buthidazole 3. Complexes of Organic Matter and Buthidazole . 4. Coordination Complexes of Tebuthiuron and Cu(II) D. Catalytic Alteration of Buthidazole by Clays III. IV. Complexes . . SUMMARY AND CONCLUSIONS LIST OF REFERENCES Photolysis of Buthidazole Bioactivity Study of Buthidazole Page 61 64 69 74 74 79 84 9O 93 97 LIST OF TABLES Table Page 1. Composition of Nutrient Solution . . . . . . . . . . . . . . 25 2. X-ray Diffraction Data of Powdered Buthidazole . . . . . . . . . . . . 28 3. X-ray Diffraction Data on the Buthidazole-clay System . . . . . . 29 4. Constants of Langmuir and Freundlich Adsorption Models . . . . . . . . . 49 5. Effect of Buthidazole on Corn Growth in Different Clays and Soils . . . . 92 vi LIST OF FIGURES Figure Page 1. X-ray Diffraction Pattern of Powdered Buthidazole . . . . . . . . . . . . l4 2. Ultra Violet Spectrum of Buthidazole in Water Solution . . . . . . . . . . l7 3. Infrared Spectrum of Buthidazole (KBr pellet) . . . . . . . . . . l9 4. Isothermic Adsorption of Buthidazole by Upton Smectite at 50°C . . . . . 34 5. Isothermic Adsorption of Buthidazole by Upton Smectite at 20°C . . . . . 36 6. Isothermic Adsorption of Buthidazole by Macon Kaolinite at 50°C . . . . 38 7. Isothermic Adsorption of Buthidazole by Macon Kaolinite at 21.5°C . . . 40 8. Plot of Adsorption of Buthidazole on Cu(II)-smectite at 50°C (Langmuir Equation) . . . . . . . . 42 9. Plot of Adsorption of Buthidazole on Cu(II)-smectite at 20°C (Langmuir Equation) . . . . . . . . 44 10. Plot of Adsorption of Buthidazole on Cu(II)-kaolinite at 50°C (Langmuir Equation) . . . . . . . . 46 ll. Plot of Adsorption of Buthidazole on Cu(II)-kaolinite at 21.5°C (Langmuir Equation) . . . . . . . . 48 12. Isothermic Adsorption of Buthidazole by Brookston Loam at 50°C . . . . . 52 vii Figure 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. Isothermic Adsorption of Buthidazole by Brookston Loam at 21°C . . Isothermic Adsorption of Buthidazole by Houghton Muck at 50°C . . Isothermic Adsorption of Buthidazole by Houghton Muck at 21°C . . Plot of Adsorption of Buthidazole on Ca-Houghton Muck at 21°C (Langmuir Equation) . . . . . Infrared Spectra of Buthidaiole a, CuCl Cu(II)-smectite buthidazole Complex c . . . . . . . . . . -buthidazole Complex b, and Infrared Spectra of CuCl -buthidazole Complexes in Different Ratios (NaCl pellets) . .'. . . . . Infrared Spectra of Transition- metal-buthidazole Complexes (KBr pellets) . . . . . . . . Infrared Spectra of Ca- and Na- buthidazole . . . . . . . . . Infrared Spectra of Buthidazole H+- and Al(III)-smectite . . Infrared Spectra of Interacted Buthidazole with Soil Organic Matter from Houghton Muck . . Infrared Spectra in Tebuthiuron System . . . . . . . . . . . Infrared Spectra of Product of Buthidazole Decomposition . . The Effect of UV Wavelength on Buthidazole decomposition . . Photolysis of Buthidazole at 254 nm (20°C) . . . . . . . . . . viii Page 54 56 58 63 66 68 71 73 76 78 81 83 86 88 INTRODUCTION The soil may be divided into two major components: inorganic and organic materials. Some of the inorganic parts are crystalline and some are amorphous. Clay min- erals play important chemical and physical roles in soils. The organicfraction is also very significant in terms of the chemical and physical properties of soils and in ad- dition is a factor in the biological ecology. Some soil scientists have stated that the cation exchange phenom- enon in soild is as important as photosynthesis is in energy conversion, and transpiration is in the uptake of water for plant growth. In terms of soil fertility and plant nutrition, the uptake of nutrients through root hairs is greatly affected by the supporting material, i.e. the soil. The clay minerals, composed of substituted alumi- num and silicon oxides and/or hydroxides, are widely dis- tributed throughout the surface of the earth. They possess large surface areas, e.g. the theoretical value of a well- dispersed smectite is as high as 800m2/g (Grim 1968). \ Research in surface Chemistry has developed for over hundreds of years. Many reports indicate that the clay minerals or their analogues have catalytic effects. Early in 1940, Faust (1940), and Hauser and Leggett (1940) found that benzidine and naphthylamines could be oxidized by some clay minerals. Ziechmann (1959) found silicic acid to be a mild heterogenous catalyst for the polymerization of hydroquinone into humic substances. Later, Mortland (1966), and Tahoun and Mortland (1966) reported that clay minerals could catalyze the decomposition of urea and glycerol. Fri- piat et al. (1966) found that the formation of an amide linkage between two amino acids was catalyzed by clay min- erals. Mortland (1970) discussed the importance of non- biochemical reaction(s) of organic compounds with clays in a comprehensive review. Recently, Pinnavaia et a1. (1979) showed that smectite could catalyze the hydrogenation of l-hexene. The mechanism by which soil organic matter enhances soil productivity is still not completely understood. But there are several hypotheses that are widely accepted. Nutrient supply was first considered since the release of N, P, S, and other elements become available after decom- position of soil organic matter. The improvement of the soil's physical properties was also one reasonable explan- ation (Martin et a1. 1955, Jacks 1963, Meredith and Kohnke 1965, and Harris et a1. 1966). Some reports showed that organic matter could supply some growth factors or inhibi- tors to plants (Patrick 1971, Chou and Young 1975). The interactions between higher plants, microorganisms and soil fauna are very complicated. The decomposed organic materials in soil combine with dead organisms and/or plant debris through degradation, condensation, poly- merization and other chemical and biochemical reactions. They form humic substances which eventually become stable organic materials whose elemental constituents do not vary greatly (Kononova 1975). However, from a microview of the functional groups, certain portions of the structure of humic substances show great diversity. The humic substances complex with clay minerals in several ways. There is no one definite structure of humic substances. They are believed to include polymers of lignins, amino acids, phenolic compounds, carbohydrates, heterocyclic compounds and other units (Felbeck 1971, Haider et a1. 1975). Much evidence suggests that increasing the amount of soil organic material would influence the phyto- toxicity of herbicides (Burschel 1961, Upchurch and Mason 1962, Upchurch and Kamprath 1966, Day et a1. 1968, Adams 1973). The adsorption of pesticides by clay has been re- viewed by Bailey and White (1970), and Hamaker and Thompson (1972). The pesticides react with soil both chemically and physically. Some adsorption of pesticides take place at extremely low concentrations, and the amount of adsorption increases with an increase in temperature within a certain range. In soil, the many different adsorption character- istics arise from the heterogeneity of the environment. Factors affecting adsorption in soil may include the chemical characteristics of the adsorbents and adsorbates, soil reaction in solution, colloidal surface acidity, temperature, and the electrical potential of the clay surface. The non-ionic herbicides are not adsorbed via a cation-exchange mechanism. Buthidazole, a newly developed broad spectrum herbicide, can be applied to the soil or to weed foliage in order to control most annual, biennial and perennial weeds. According to the primary reports (Vel- sicol Co. 1977, and Mullison 1979), its application to sorghum, sugarcane, alfalfa, pineapple and certain tree crops appears to be most promising. While the reaction mechanism of buthidazole is still uncertain, it no doubt is a photosynthetic inhibitor. York and Arntzen (1979) found that inhibition in the Photosystem I-electron trans- port, cyclic photophosphorylation and phenazine metho- sulfate-mediated proton uptake was insignificant. A major effect of buthidazole is inhibition of electron transport on the reducing Site of Photosystem II. Systematic re- search from a physiological point of view, i.e. adsorption, metabolism, and translocation within the plant, mode of action, selection, and antidotes, have been reported in Hatzios' dissertation (1979). The electron configurations of imidazole, carboxyl and thio groups suggest an ability to complex with some transitional metal ions. The non-ionic properties inhibit possible adsorption by clays via a cation exchange system. Solubility (0.61%, w/w) in water is sufficient for experiments simulating field soil conditions. I sought to reveal mechanisms of interaction between this new herbicide and homoionic clay minerals, and describe the characteristics of its complexes with transitional metal ions. Some selected soils were also studied with respect to their capacities for adsorption of this compound. Hopefully, the results of this study will contribute more knowledge about reactions of this compound in soil, and a better understanding of residue problems. Statistical data shows that the application of pesticides can be a very economical way of enhancing agricultural production (Black 1977), and this, inpart, provides motivation for this study. LITERATURE REVIEW Clay minerals are chemically very stable, so much so, that they are widely distributed throughout the outer Shell of the earth. For many years, studies focused on the geological changes of clay minerals, such as diagenesis, weathering, etc. The reaction of clay minerals and organic matter was early mentioned by Faust (1940), and Hauser and Leggett (1940). They discovered color changes of aromatic amines, such as benzidine and naphthylamines, which were oxidized by some clay minerals. Ziechmann (1959) found that silicic acid could catalyze the polymerization of hydroquinone. They pointed out the chemical reactivity of clay minerals with organic materials. Mortland and Halloran (1976) showed that Cu(II)- or Fe(III)-smectite would catalyze the polymerization of adsorbed benzene and phenol. Wang and Li (1977) reported that clay minerals can also catalyze the polymerization of phenolic compounds to a certain extent. They stated that these reactions could be relevant to the nonbiological occurrence of organic polymerization in soil. Most clay mineralogists are inter- ested in the surface chemistry of clay minerals, especially the expansible smectites. Recently, Pinnavaia and his coworkers (1979) successfully used rhodium-triphenyl- phosphine complexes intercalated in smectite to catalyze the hydrogenation of l-hexene. Mortland and Berkheiser (1976) discovered that TED+2-smectite could catalyze the acetonitrile to form acetamide, but TED+2-vermiculites were unsuccessful in this catalysis (TED = triethylene diamine). Bailey and White (1970) classified the mechanisms of adsorption into the following categories: (1) Physical adsorption (2) Chemical adsorption (a) Ion exchange (b) Protonation (3) Hydrogen bonding (4) Coordination In practice, there is no clear boundary between these four categories. By studying the adsorption of herbicide EPTC by montmorillonite, Mortland and Meggitt (1966) showed that the Cu, A1, and Co ions coordinated with EPTC through the carbonyl group. Sund (1956), Ercegovich and Frear (1964) stated that amitrole adsorption was related to the metal ions in clay. Russell et a1. (1968) explained that the coordination of the amitrole with polyvalent cations, such as Ca(II), Cu(II), Ni(II) and A1(III) was due to protona- tion. In research of organo-mineral interaction, infrared spectroscopy is widely used in revealing these mechanisms. IR spectra in different incident angles of montmorillonite film gives good information about the aromatic Organic orientation in the clay lattice. Serratosa (1966) success- fully interpreted the pyridine configuration in montmoril- lonite interlayers from in-plane or out-of-plane vibrations in the IR spectra along with X-ray-diffraction data. Schnit- zer and Skinner (1963) found that organic matter formed stable water soluble complexes with Fe(III), Cu(II) and A1(III). Sund (1956) reported amitrole formed complexes with Ni, Co, Cu, Fe and Mg ions. Ashton (1963) proved that Ni, Co and Cu combined with amitrole using autoradiography. Mortland (1966) discovered the urea complexes with Mg-, Ca-, Li-, Na- and K-montmorillonite through N-H bond ionization, but with Cu(II)-, Mn(II)-, and Ni(II)- montmorillonite through carbonyl group coordination. Tahoun and Mortland (1966a, b) stated that the order of the bonding strength of metal ions in montmorillonite with a given amide is Transition :> Alkaline earth :> Alkali metal For a given metal ion, the order of binding strength for amides is Tertiary > Secondary > Primary Parfitt and Mortland (1968) studied the adsorption of ketones by montmorillonite systematically and found that acetone was held more strongly on Cu(II)-montmorillonite compared to Na-, Ca-, Mg-, and Al-montmorillonite. Doner and Mortland (1969a, b) found that organic-cation-montmorillonite adsorbed the NH-CO compounds by hydrogen bonding. They also found that benzene complexed with Cu(II)-montmorillonite, but not with other homoionic montmorillonites. These studies employed IR-spectra and color changes. Mortland and Pinnavaia (1971) reported that benzene formed two different complexes with Cu(II)-montmoril- lonite under different moisture contents. By using the IR absorption of hydroxylatrazine at 1745 cm-1, Skipper et a1. (1978) discovered that H+- and A1(III)-montmorillonite could promote the hydrolysis of atrazine but Ca(II)- or Cu(II)- montmorillonite failed to do so. Humic substances are classified into (a) humic acid which is alkaline soluble but acid insoluble, (b) fulvic acid which is both alkaline and acid soluble, and (c) humin which is both alkaline and acid insoluble. The reaction of pesticides with humic substances had been reviewed by Hayes (1970), Stevenson (1972a, b) and Khan (1972). They listed the possible mechanisms of reactions of pesticides and humic substances, and stressed the importance of the soil organic matter in adsorption of pesticides. Hydrogen bonding and chelation through metal coordination were the most important in adsorption according to their reports. Kahn (1974) stated that the IR-spectra of humic and fulvic acids changed when they reacted with diquat and paraquat. Photolysis of pesticides has been reported by Mitchell (1961). He detected the decomposed products of 141 10 pesticides by paper chromatography, but he did not identify them. Most of the photodecompositions were simple ones which did not change the structural skeleton very much, e.g. hydrolysis, dechlorination or demethoxylation (Pli- mmer 1970). Joschek and Miller (1966a, b) reported that upon photocleavage Of phenols, free radicals were formed first, and later polymerization followed. Krantz and Laureni (1977, 1978) have reported that irradiation of 1, 2, 3—thiadiazole derivatives formed compounds shown below: :2]— (\ 21m: ”I R\—"S Rl\_"/R1 R _ R The above illustration Of the photodecomposition of the thiadiazole derivatives, points out the variety of products that may occur in this kind of reaction. MATERIALS AND METHODS Preparation of Homoionic Clays Smectite (Upton Bentonite, Wyoming) and kaolinite (No. 4, Macon, Georgia) were chosen as the clay minerals for this research because of their typical expansible and nonexpansible properties, respectively. The CEC of smec- tite and kaolinite are 92 and 12 m.e./lOOg clay, respec- tively. Both clay minerals were well-dispersed at pH 9.1 using Waring blender. Then the finer clay fractions (< 2p) was siphoned out according to Stokes Law (Day 1965). 2, 2, and A1Cl3 were added to aliquots of the clay suspension and equilibrated with The salts of NaCl, CaCl CuCl stirring. Clays were allowed to settle or thrown down by centrifugation, and the supernatant solution discarded. The process was repeated again and again until the super- natant was'free from the other cations. Then the homoionic clay suspension was dialyzed in distilled water until chloride free, freeze-dried, and stored for use. To make H-clays, the Na-clays, Upton smectite and Macon kaolinite, were dispersed in 2%(w/v) suspension by a supersonic agitator and passed through the H-resin (IR-120, Lot No. 2444). Then H-clays were freeze-dried, ll 12 stored in refrigerator to slow down the destruction of Al-silicate structure. The pH's of the H—smectite and H-kaolinite were 2.65 and 3.50, respectively. Preparation of Soil Samples Two kinds of soil samples, Brookston loam and Hough- ton muck, were prepared for this research. The A1 horizon of Brookston loam contained 44% silt, and 16% clay and organic matter content was 5.17%. A cation exchange capacity (CEC) of 16.3 m.e./100g was found by the NH4OAc method (Chapman 1965). Soil reaction was neutral. Parts of the Brookston loam sample were oxidized by H202 to destroy the organic matter. Houghton muck contained 42% organic matter and the reaction was slightly acidic. The CEC was found to be 49.6 m.e./100g by the NH4OAc method. Portions of the Houghton muck were washed with solutions of CaCl and CuCl2 by leaching to make the Ca and Cu(II) 2 forms. Excess salts were washed out with distilled water. Properties of Buthidazole This herbicide was offered by the Velsicol Chemical Corporation, as an analytical reference standard (98.7% purity by IR). Its product name is RAVAGE. This authentic material was recrystallized from 30% n-hexane in methanol twice. It forms needle-like crystals. The powdered X-ray diffraction pattern is shown in Figure 1. From X-ray diffraction data, this herbicide crystal appears to be 13 I o x .H wusmflm 32.3.. v Q ~ m o. m. om ma an- - . .4141141. 1 J1111~1qull1lldx 231 iisxéfiééfié is... 1 l4 bPlbbbbbbLbbhbr LIP P p p .r P P b lb L — L PibllLll—li-»iLiul—lvlrllh- lPIl-lLlibiIl—iulbsllb P 5 pr b b b msuim 15 orthothmbic. The solubility in water is 0.61% (w/w). The heterocyclic N does not impart much basicity of the molecule. The titration curve Of buthidazole in water does not Show an inflection point, and therefore, pK has b not been determined. UV—visible spectra showed an absorp- tion maximum at 253 nm (Figure 2). Its molar absorptivity 4 molar-lcm_l. This property is very reaches 1.3 x 10 convenient in the quantitative determination of this com- pound by UV-spectrometry. Its IR spectrum is quite compli- cated (Figure 3). (I’ll c —u — "3% ll ? ”'2 "30—; _ \s/c-N\c/ “CH3 cu3 Buthidazole (3-{5-(1,1-dimethylethyl)—1,3,4-thiadiazol-2-yl} -4-hydroxy-1—methy1-2-imidazolidinone) Intercalation of Buthidazole in Smectite To determine if the adsorption phenomena of buthi- dazole by Upton smectite involved interlamellar penetration, the d-spacing of smectite was measured by X-ray diffraction methods. This diffractometer has filtered Cu Ka radiation and is manufactured by North American Philips Co. Inc. l6 .:0HusHom Hmucz ca mHonCflcusm mo Esuuoomm DTHOH> cuuHD .N musmflm 17 con own .dll.-ll. T1..- a ._ £55.25 cw.” .DIll-llb- l; I)... I con .. om“ Bu libwm-----.--bmu . ecu nmu .l. u u s m “C n... o u l8 .Aumaamm ummv mHonwwnusm mo Esuuommm CTHOHMCH .m musmflm 19 O— N— 73: co: £2522; gmsueil uogss 20 Buthidazole was added to Al-, Cu-, Ca-, and Na- smectite suspension or clay films at the buthidazole-clay ratio of 0.5:1 and 4:1 (mole/equivalent in CEC) in water. After equilibration (48 hours), the clay films were washed with distilled water to remove the excess buthidazole. The clay suspensions were centrifuged and oriented on microscope slides for X-ray diffraction studies. Then they were heated to 110°C, 300°C, and 400°C stepwise and diffraction data obtained at each point. Cupric chloride and buthidazole were mixed in differ- ent ratios (0.5:1 and 1:1) and then air-dried. This crystal mixture powder was studied with X-ray diffraction to see if there was a coordination complex formed between Cu(II) and buthidazole. Thiophene and the analogous herbicide, tebuthiuron, were also examined by X-ray diffraction for the possibility of forming coordination complexes with Cu(II). c __ l l " VH3? — "30-0— \ ,u-N-c-Hflg I 5 II a’ Ofl3 o Thiophene Tebuthiuron thiadiazol-Z-yl}-N,N'-dimethylurea 21 Adsorption of Buthidazole on Clay Minerals and Soils Adsorption isotherms were obtained for this compound on smectite, kaolinite, Brookston loam, and Houghton muck. Fifty mg of smectite was added to each of the 20-ml buthi- dazole solutions at different concentration, ranging from 0.5 to 10 mM. The clay minerals were dispersed homogen- eously in the solutions with a supersonic agitator. The mixtures were shaken by hand occasionally and equilibrated for 48 hours at 20C and 50C, respectively. The suspensions were then centrifuged to separate the clay from the solu- tions. An aliquot of the supernatant was taken for analysis of unadsorbed buthidazole using UV spectrometry at 253 nm. The amount of adsorption was calculated by subtraction from the original amount added. A Beckman DK-2A Ratio Recording Spectrophotometer was used both for scanning the whole spectrum and for quantitative analysis. The buthidazole adsorption on Macon Kaolinite was also performed in the same manner except that the concen- trations of adsorbate were considerably lower than those used in the Upton smectite experiments (Ranging from 0.1 to 2 mM), since preliminary experiments showed that the adsorption amounts were lower than those of smectite. The two soils contained low amounts of clay, therefore larger sample size of the adsorbents was needed. One hundred mg soil for each replication was chOsen instead of 50 mg as in pure homoionic clay minerals. The 22 concentration of compound used was the same as in kaolinite experiments. Infrared Spectroscopic Study The homoionic Upton smectite was suspended in water and dispersed by a supersonic agitator. Then the suspensions were poured onto polyethylene sheets or aluminum foil and .dried at 40 to 50C. The thickness of the clay films was 1 to 2 mg/cmz. The films were soaked in buthidazole-water solution, at several concentrations. The film was then quickly washed with distilled water to rinse off the excess buthidazole, air-dried, and scanned through the range 600 to 4000 cm"1 with a Beckman-IR? Infrared SpectrOphoto- meter. The reactions of thiophene and tebuthiuron with Upton smectite were studied with IR spectrOSCOpy to deter- mine the bonding during intercalation of buthidazole. The complexes of Cu(II) and buthidazole were made by mixing CuCl2 and buthidazole solution in the ratios 1:1 and 1:2 as before. The mixture was then dried. A NaCl pellet was made for the IR studies instead of KBr, since CuBr2 formation during high hydraulic pressure resulted in a reduction in transmission of the pellet. Nickel(II), coba1t(II) and iron(II) complexes with buthi- dazole were also scanned in IR region as in Cu(II). Desorbed buthidazole and water extracted organic matter from Houghton muck was studied by IR. Fifty- milliliter of water was added to 5g of Houghton muck and 23 shaken overnight. One-milliliter of the yellowish brown extract was added to 0.5 m1 of 0.01M buthidazole, dessicated alongside phosphorus pentoxide until dry, and then scanned in the IR region. The dry-weight ratio of water extracted organic matter and buthidazole is around 1:1. Photolysis of Buthidazole The buthidazole water solution was irradiated at 254 and 366 nm in the ultra violet region. A mineral light lamp Model UVSL-58 from Ultra-violet Products, Inc. was used. Buthidazole 2 x 10-4 M was irradiated in stop- pered silica cuvettes. The sample was scanned in the UV- visible range. The decrease of absorbance at 253 nm was measured as an indication of degradation or other change of this herbicide. Larger volumes of buthidazole solution were irradiated in an attempt to convert enough compound(s) 4 M buthi- for IR detection. Fifty milliliters of 2 x 10- dazole was put in a 90mm(dia) petri dish, with aluminum foil at bottom (outside) to enhance the light intensity of irradiation by reflection. The solution was irradiated with 254 nm UV-light for 100 hours, evaporated and dried alongside phosphorus pentoxide. A KBr pellet was made and scanned in the IR region. A high concentration of buthidazole will decrease the penetration of the UV-light, leading to a low percentage of photoconversion of the compounds. The solution mixtures of buthidazole and different salts (CuCl2 and CaClz) were also irradiated, to test photodecomposition rate in metal complexes. The 24 mixture was in the ratio CaCl2 (or CuClZ):buthidazole = 1:1 (mole/mole). Bioactivity Study of Buthidazole (1) Formulation of Nutrient Solution for Sand Culture The formula of the nutrient solution in this experi- ment was designed by Arnon and Hoagland (1940). The compo— sition of the solution was listed in Table l in detail. (2) Preparation of Quartz Sands in Sand Culture IWedron silica from Wedron Plant-Wedron Silica Division was used in this experiment. The diameter ranged from 0.3 to 1.0 mm, with 99.9% purity. The quartz sand were washed with 0.lN HCl and 0.1N NaOH and then rinsed with distilled water. The water holding capacity is around 8.5% and bulk density around 1:8. These data were used in preparing the pots and in irrigation during the growth period of the corn. (3) Tested Plant: Corn Corn (E23 gays, Michigan 407) seeds were provided by the Department of Crop and Soil Sciences, Michigan State University. The seeds were soaked in a wet filter paper in petri dish to incubate for 2 days at 25°C. Those of the same shape were selected for the assay study. (4) Cultivation of the Tested Plant Techniques and principles of bioassay stated by Hurle (1977) were followed. Buthidazole 0.75 and 7.5 mg were added to 1.5g clay or soil suspension 50 ml, 25 Table 1. Composition of the Nutrient Solution Chemicals KNO3 NH4H2PO4 MgSO4.7H20 H3BO3 MnCl .4H 0 2 2 4.5H20 ZnSO4.7H20 H2M004.H20 FeSO4 solution 0.5% CuSO Tartaric acid 0.4% Concentration 1.02 g/l (0.01M) 0.708 g/l (0.03M) 0.230 g/l (0.002M) 0.49 g/l (0.002M) 2.68 mg/l 1.81 mg/l 0.08 mg/l 0.22 mg/l 0.09 mg/l 0.3 ml/l 0.3 ml/l 26 respectively, equilibrated for 24 hours. The suspension was transferred to 750g of quartz sand, mixed thoroughly, and air-dried. The quartz sand was placed in 500 ml-plastic cup with a hole in the bottom. A pre—germinated corn seed was then planted. The sand culture was irrigated from bottom with nutrient solution to prevent the leaching of the clay particles and herbicide. Generally, the field application of buthidazole ranged from 0.3 to 0.45 kg/hectare of soil. In this experi- ment, the buthidazole was mixed thoroughly in the sands and the rate was around six times the field application at low level. Irrigation was continued every other day until harvest (15 days). Three replicatiOns were performed for each treatment. A buthidazole-free series were also carried along as a control test for comparison. The growth condition and dry weight were measured. RESULTS AND DISCUSS ION I. Crystal Structure of Buthidazole The newly developed herbicide, buthidazole, 3-{5- (1,1-dimethylethy1)-1,3,4-thiadiazol-2-yl}-4-hydroxy-l- methyl-Z-imidazolidinone, is made up of white needle-like crystals. The empiricalformula is C10H16N4OZS. The powdered X-ray diffraction pattern (Figure 1) showed that it is very close to the orthorhombic (a s b s c, a=8=y=90°). The theoretical values (calculated) and the experimental values of the peaks are listed in Table 2. The unit cell dimensions are a = 11.73A, b = 11.10A, and c = 9.27A. II. Adsorption Phenomena of Buthidazole on Clay Minerals and Soils A. Swelling Properties of Clays The thickness of the buthidazole molecule would be around 4.23A, theoretically calculated from the radius of iso-butyl group: 1.54A {I + Cos (180° - 109.3°)} + 1.09A x 2 = 4.23A where the average distance of C-C bond and C-H bond are 1.54A and 1.09A, respectively. As indicated in Table 3, the X-ray diffraction patterns of the lower buthidazole-Clay 27 28 Table 2. X-Ray Diffraction Data of Powdered Buthidazole 28 d observed(A) hkl d calculated(A) Intensity 8.63* 9.2515 001 - w 9.55 9.3531 001 9.2655 vs 15.13 5.8507 200 5.8656 m 15.26 5.8012 ? ? 5 16.04 5.5208 020 5.5478 S 17.30* 4.6283 002 - w 17.62 5.0291 120 5.0153 w 19.11 4.6402 002 4.6328 vs 19.64 4.5162 211 4.5251 3 21.60 4.1106 220 4.0306 w 22.72 3.9104 300 3.9104 m 24.14 3.6835 030 3.6881 m 25.20 3.5309 130 3.6985 w 26.36 3.3781 122 3.5274 m 26.76 3.3285 ? ? m 26.98 3.3019 131 3.2966 w 28.85 3.0920 003 3.0885 v 30.83 2.8978 400 2.9328 w 32.96 2.7152 040 2.7626 m 36.28 2.4740 240 2.5076 w 36.59 2.4537 223 2.4515 w 38.76 2.3212 500 2.3462 m 38.86 2.3155 004 2.3164 m 39.47 2.2811 050 2.2191 w 45.00 2.0128 440 2.0153 w 45.10 2.0085 ? ? w 46.40 1.9552 600 1.9552 w 49.00 1.8574 ? ? w 49.12 1.8531 005 1.8531 w 49.23 1.8493 060 1.8493 w *Diffraction of K81(1.39217A) of COpper # vs = very strong; strong; m = medium; w 29 Table 3. X-Ray Diffraction Data of Buthidazole-Clay System Exchange d -spacing(A) . 001 Cation Air-dried 110C 250C 300C 400C Untreated Smectite Cu 12.44 12.0 9.6 Ca 15.21 13.0 9.6 14.47 A1 14.02 12.1 9.9 .14.70 Na 11.78 9.8 9.8 H 12.5 9.9 9.9 9.9 Buthidazole-Intercalated Smectite Cu 12.8 13.5 12.6 11.2 Ca - 14.3 14.1 14.1 10.9 A1 13.8 13.8 12.6 11.0 Na 13.6 13.4 10.9 H 13.0 13.0 12.8 13.6 3O ratio (1:2, mole/equivalent Charge) showed that the air— dried buthidazole smectites have a d-spacing ranging from 12.8 to 14.3A. When they were heated to 110°C, the d- spacing still remained about the same. This means that buthidazole entered into the interlamellar space of the expansible clay minerals. Further heating caused a little destruction of the herbicide (Table 3) and disruption of the spacing. The decomposition temperature is 237°C (Mullison 1979). After heating to 400°C, the diffraction peak became broader. Some heat-decomposition products still remain in the internal regions and lead to the ir- regular periodicity of the layers. At higher buthidazole— clay ratio (4:1), more layers of buthidazole entered the lattice. Some of air-dried lattice spacing reached 19.6A, which could be two or three layers of buthidazole. No Significant difference in d-spacing in the smectite was observed for different exchangeable cations after treatment with the compound. B. Isothermic Adsorption of Buthidazole 1. Adsorption Models The buthidazole is neither a good proton donor nor a good proton accepter in water solution. The water sol- ution of buthidazole is almost neutral. Though it contains many heterocyclic nitrogens, the acid-base titration curve does not show any inflection in water. Thus the adsorption phenomenon is naturally not due to ion exchange. The X-ray 31 diffraction study described earlier showed that the mole- cules of the buthidazole could get into the interlayer of the expansible clay just as those of glycerol or ethylene glycol reported by Brindley (1966). Some of the results are plotted according to Lang- muir and Freundlich adsorption models. The equilibrium can be shown as K1(adsorption) \ B + Clay B—Clay )I K2(desorption) Where B denotes buthidazole; then in the Langmuir equation: KbC 1 + KC where: x is the amount of adsorption per unit weight of adsorbent. K K = E; , which is equilibration constant of adsorp- 2 tion desorption. C is concentration of buthidazole. b is the maximum amount of adsorption. After manipulation, the equation becomes: 0 _ 1 1 ‘fit-S'C 8D< When C/x/m is plotted against C, empirical b and K can be 32 determined. In the Freundlich model, the equation is x/m = KCl/n or log(x/m) = l/n log C + log K If log (x/m) is plotted against log C, then K and l/n can be obtained. 2. Isothermic Adsorption of Buthidazole on Clay Minerals The adsorption isotherms Show that the Cu(II)-smectite adsorbs 5 to 6 times as much as Cu(II)-kaolinite (Figures 4, 5, 6, and 7). In Cu(II)-clays, the adsorption data obey Langmuir adsorption model very well (Figures 8, 9, 10, and 11). From Table 4, the results of adsorption showed that the maximum amount of adsorption by Cu(II)-smectite (150 and 126 m moles/100g at 50°C and 20°C, respectively) is larger than that of Cu(II)-kaolinite (29 and 21 m moles/ 1009 at 50°C and 21.5°C, respectively). The K values are larger at the lower temperature for the same clay. This suggests the adsorption is exothermic. The most interesting thing in the adsorption phenom- ena is that Cu(II)-clays adsorbed much more buthidazole than those of the other metal—clays in the concentration range of interest (Figures 4, 5, 6, and 7). This suggested that the coordination of Cu(II) and the buthidazole took place. The Cu(II) ion can from many complexes with organic ligands. The complexes were formed by the donation of 33 .UOom um muwuowEm scum: >2 mHonpwnuzm mo :ofluQHOmps omeumcDOmH .v musmflm 34 s... .2525: 13.2.3 1:: a n o n v n N — \I J 1 n u 1 2:35. : < 2:35.: . ‘1‘“ , \ o C: o 0 Q *0 V N p- a SooI/salom m ‘paqmspv alozepgqing lo '1'” DO 6 N o: £2 35 .UOON um mufluomfim scum: >9 mHoncflcusm mo :OHumH0mC4 CHEMOCDOmH .m musmflm 36 53 6.32.23. 2 .355 5...: o. o a a o , m c n u _ o O N O V O O a a 6 9. m: Boat/snow In ‘paqmsw anzepmna Io 'imu \\ 4 \ Camcoo—Emo a: n 223......- 3 .. 2:25- _ a a 328...”. .5 ON— 37 m . m uficfiaomx coomz >9 mHonnwnusm mo COHDQHOmcm UHEWMMMOMH .m musmflm 38 :53. a v.— .:=~<=.=;a 3 .2289 2:93v 0.0 0.. a; 6.. ad \C\ CAMII. I.N“W°6\III\° 49:-dc < 43?: c 2:23-: n 42:59 o "In SOOI/SB‘IOW II ‘IBSIIOSIIV NOZVOIILIIIS O— a. .v- c— :IO 'lWII 39 .UOm.HN um muficflaomm coon: xn OHONmpflcusm mo coflumu0mU< oHEuTQDOmH .5 musmflm 4O 53:: 8 $3325.... 3 .2239 453 o.~ oh— 0.; .m— «m . Om:— od 0.0 to «.0 o G I \\ O o . N \\ I . o \ . v \o o O\ . O . o 43..-: a .2 :55. .. 5 u 42..-: a a. .85.- =9 . . v— AV'IO SON/SNOW III ‘GJHIIOSOII JIOZIIIIIIIIIIS :IO 'lWV 41 Figure 8. Plot of adsorption of buthidazole on Cu(II)- smectite at 50°C (Langmuir equation) (10'3) C/X/M 42 O 0 r2: 0.9827 /0 I'0 0 I 2 3 4 5 J7 EQIIIL COHEN” M MOLAR 43 Figure 9. Plot of adsorption of buthidazole on Cu(II)- smectite at 20°C (Langmuir equation). I-‘ _ 1 _ + b C gal. 71 U‘ (10‘3) C/X/M 44 r2 = 0.9978 I- o I I 1 L 1 i O 'l 2 3 4 5 6 7 [NHL CONCN., M MOLAR 45 Figure 10. Plot of adsorption of buthidazole on Cu(II)- kaolinite at 50°C (Langmuir equation). BINIO ’21 U‘ U‘ (10'3) c/x/II 46 12 .- 0/ IO " r2 = 0.9815 4 I- 2 .- O 1 1 l 1 l l l I 1 0 0.2 0.4 0 6 0.3 1.0 1.2 1.4 1.6 1.8 EQIIIL. CONCN., M MOI-AR 47 Figure 11. Plot of adsorption of buthidazole on Cu(II)- kaolinite at 21.50C. (Langmuir equation). 1 l "755‘“‘15—‘3 BIXIO (10‘3) C/X/M 48 14L r2: 0.8766 o l I 1 I 1 1 1 I A 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Lb 1.8 EQUIL. WHOM, III MOUIR 49 Table 4. Constants of Langmuir and Freundlich Adsorption Models. Exchangeable . . Cation or gemp. Langmuir Freundlich Treatment C K b(m moles K n ‘100g ) Smectite A1 50 - - - - Cu 50 0.5775 150 48.144 1.8042 Ca 50 - - - - ' Al 20 - - 10.638 0.8906 Cu 20 0.7808 122 45.308 1.7994 Ca 20 - - - - Kaolinite Al 50 - - 2.775 0.8468 Cu 50 0.6097 29 12.279 1.0107 Ca! 50 - - - - Na 50 - - 2.884 0.7875 A1 21.5 - - - - Cu 21.5 0.9584 21 - - Ca 21.5 - - - - Na 21.5 - - - - Brookston Loam Natural 50 - - - — w/o OM 50 - - - - Natural 21 - - - - w/o OM 21 - - - - Houghton Muck Natural 50 - - - - Cu: 50 - - 1.551 1.0355 Ca 50 - - - - Natural 21 - - - - - Cu 21 0.1537 18 2.425 1.4627 Ca 21 0.0787 22 1.555 1.1500 *Blank (without datum) means low correlation in the tested model. 50 electron pairs by the buthidazole to the Cu(II). It is proposed that the electorns were donated by the oxygen atom in the carboxyl group to Cu(II). The complex formation by exchangeable Cu(II) in clays is strong enough to reduce the concentration of buthidazole in solution. Attempts to detect the complexes as crystallized entities using X-ray diffraction failed. However, infrared spectrOSCOpy succeeded and will be dis- cussed later. 3. Isothermic Adsorption of Buthidazole on Soils The isothermic adsorption of pesticides by soil depends on several factors, such as surface area, soil reaction, surface acidity, organic matter, etc. (Bailey and White 1970). The organic-matter free Brookston loam adsorbed less buthidazole than natural one at 50°C (Figure 12) as most reports stated, but the amount absorbed was not significantly different at 21°C (Figure 13). In Hough- ton muck, which contains about 42% organic matter, the amount of adsorption indicated that the effects of different cations are not as great as in clays. -This suggests that the organic matter itself predominates in the adsorption of buthidazole in organic soils (Figures 14 and 15). 4. Thermodynamic Considerations from the Isothermic Adsorp- tion of Buthidazole Normally, the higher the temperature, the less the adsorption. But in this adsorption experiment, some of 51 .OOom um Smog coumxooum xn mHonpflcusm mo cowumuompm OHEchuomH .NH musmflm 52 < < E 5' =5 :2 ‘5' G a: n: g— at— ; B 1 D I I I l I I Q. 05 O Q '0 V —- - —= o o‘ 6 INS flow/SNOW W ‘IIEIHIIOSIIII BIOZIIIIIIIIIIG :IO '.lWlI EQIIIL ONION. 0F BIIIIIIIMIIILE, M HOUR 53 . UOHN HM SODA coumxooum >3 wHonpflnusm mo :oflumHOmpé anumnuomH .MH wusmflm :55. 5 £322.53 .3 .2923 453 as a _ 3 I S 3 ad ad to me o - q d d d 54 .8 .e 2; < \\ . N0 I ‘0 0.0 0.0 .0.— N.- . V.— 0.. INS 9001/5310“ W 13880807 SIOZVIIIIIIIIS :IO '1'” 55 .DOom um x052 coucmsom an mHonpflcusm mo coflumnompa OHEHOLDOmH .ea Guzman d 56 IO O a Is 0 In cc I \\ W I u‘ 9 a E ‘3 52= .EE ~ «an :99 <0- 0 1 1 1 Q N O '0 P — — ”as SOOI/sanuI III ‘PWOSPV anzevIlIms 40 WW Email. Comm. of IIIIIIIIIIaloIe . 57 00 .m x052 coucmsom >3 mHonpflcusm mo :oHumHOmp< anuwwmowH .mH musmflm 58 2... 3.32.225 .s .355 .____E o. a s n e _ n a _ o a q a J a q a q \ o v \. .u m... a m. 4 m P d a v fl\.. «4. , -o m \. m. . . w .a m m. .23. 3 ._ N m ‘2...— so a .o— 0 I 3 \a\ .3... .23... a m. \ .2 59 the results did not indicate a general exothermic reaction. The reason might be due to the enhancement of the solubility of buthidazole in water at higher temperature. Exceptions to expected exothermic reactions have been reported for some herbicide adsorptions at different temperatures. Harris and Warren (1964) found that diquat had the same adsorption at 0 and 50°C. Freed et al. (1962) found increased adsorption of S-ethyl dipropylthiocarbamate (EPTC) at higher temperature. From the solubility-tempera- ture effect on the adsorption of benzene hexachloride (BHC) by soil, Mills and Biggar (1969) discovered the competition of nonpolar BHC and water led to the fact that adsorption increased with rising temperature. They stated that the amount adsorbed is not only dependent on the energy of adsorption, but also on the effect of temperature on the adsorption of BHC. McClamery and Sliffe (1966) also stated that more atrazine was adsorbed by humic acid at higher temperature. From the equilibrium constant of Langmuir's model of adsorption (Table 4), we can calculate the molar heat of adsorption, AH, for the buthidazole adsorbed by Cu(II)- smectite and Cu(II)-kaolinite, both of which exhibited more normal temperature dependence. Using the Clausius- Clapeyron equation: K 2 AH l 1 1n ‘-—(———- ) Kl R T2 T1 K R In 2 K1 or AH = - l - 1 T2 1 where K1 is the equilibrium constant of adsorption at temperature Tl’ K2 is the equilibrium constant of adsorption at temperature T2, R is the gas constant. Using this formula, AH for Cu(II)-smectite is -l900 cal mole"1 and AH for Cu(II)-kaolinite is -3000 cal mole-l. These values are near those found for Cu(II) complex formation with other ligands. 5. Relationship of Laboratory Studies to Field Application Some of the adsorption data at the concentration range of interest appeared to be a linear relation between the amount of adsorption and the concentration. This is not surprising because at low concentration, the desorption constant K is negligible: 2 KKC x _ 1 2 . i=KKC or—’-‘—--Kc hreK-KK m 12 m“ 'we ‘12 The final equation indicates that at low concentration, the amount of adsorption, x/m, is directly proportional to the concentration, C. In practice, the concentration 61 of the field application is very low. According to the Herbicide Handbook (Mullison 1979), the application rate is 0.33 lb./acre, or 0.36 kg/hectare. If the field moisture is kept at 20% of the top l-cm soil, the amount of adsorption, x/m, and equilibrium concentration, C, can be calculated by the following system of equations: 0 '..: '..: X SIX (A) or (B) 39' ll 0 <: + Ix 2 3’ ll 0 <1 + 2 where A is applied amount of buthidazole per hectare (0.36 kg), V is the water moisture content in top l-cm soil 4 . . . (2.6 x 10 kg), w 13 the weight in top l-cm soil (1.3 x 105 kg). Then in Ca-Houghton muck at 21°C, the estimated amount of adsorption reaches 98.7% of application according to equation (A), (Langmuir model, Figure 16). In natural Houghton muck and natural Brookston loam (with organic matter) at 21°C, which are estimated by equation (B), they are 77% and 75%, respectively. C. Complex Formation of Buthidazole The infrared spectroscopy was used as an important tool for complex study. The IR spectrum of buthidazole is very complicated (Figure 3). In the finger print region of the IR spectrum, many bands affect each other. The possible 62 Figure 16. Plot of Adsorption of Buthidazole on Ca- Houghton Muck at 21°C (Langmuir Equation). _ l l ‘ Kb + bC 8...]. c/X/M (10'?) 10)- 63 r2: 0.7941 2 3 Equil. Concn.. III M L. 64 atoms of interest in terms of coordination, N, S, O, in this molecule are assigned several bands. By using clay- film techniques, some problems in clay surface chemistry have been solved. It is known that the mercaptan organic compounds, which contain sulfur atom(s), would coordinate with the Cu or other transition metal ions. Buthidazole contains one sulfur atom in the l, 3, 4-thiadiazole ring, however the C-S-C linkage does not coordinate with Cu(II) as >C = 0 does. 1. Coordination Complexes of Buthidazole with Transition Metals The complex formation of Cu(II) and buthidazole has been proved by the change of IR spectrum (Figure 17). A very strong band at 1720 cm.1 due to original buthidazole C = 0 stretching, shifts to 1690 cm.1 when Cu(II) is present. Carboxyl oxygen shares the electrons with Cu(II). The exchangeable Cu(II) in the smectite results in the same coordination phenomena as free Cu(II). The 2>C = 0 stretching band of buthidazole at 1690 cm-1 is affected by Cu(II) coordination and is similar to acetone complex- ation with Cu-montmorillonite (Parfitt and Mortland 1968). The IR spectra (Figure 18) also showed that the shift of the carboxyl band depends on the ratio of cation to ligand. No crystal formation of this coordination complex was detected by X-ray diffraction as mentioned before. The complex is not stable in this sense. If the 65 .o memEoo mHmNmpwsusnnmufluomEmlAHHVSU can .n xmameoo oHonpwnusnl H050 .m mHonpfinusb mo muuowmm commumsH .nH oudmflm 66 O— .-.5 oo— ~ 52.55:: a. 3 o. o— “ ‘ 0691 2. 4 8891 ,OZLL 7'3)" "" .‘fi— b '---‘-- .. uogssgmsuul 67 maoumegnusm .o mHonnflgusn . maoso .n mHoncflsusn . maoso .m N H H H II II .Amumaamm Humzv mOwumu NHUSU mo muuommm UmumumcH unmumMMHU CH mmxmamaoo mHoNMpflnusni .mH musmflm 68 7.3 $2.53.; 8... . 8.. 2.5. new. 8.... co... co... a O u w m 11.. . ‘a I x? . p p b p . n - uogssgusuul 69 buthidazole to Cu(II) ratio is l to 1, the band at 1720 cm-1 almost disappeared. But if the ratio increases (for example, 2:1), then both bands coexist. This suggests the presence of both complexed and uncoordinated forms. From the stoichiometric study, the ratio of ligand and Cu(II) is 1 to 1. The other coordination members of this complex are suggested to be water molecules. Thiophene was chosen as a model molecule with ring sulfur to check the coordination complex formation with pure Cu(II) and Cu(II)-smectite system. Through IR spectral analysis, it seemed that no complex formed. The thiophene molecule could get into the clay interlamellar space and gave a d-spacing of 13.2A. Other transition metals such as Ni(II), Co(II), and Fe(II) were successful in making coordination complexes with buthidazole. They were also detected by IR spectra (Figure 19). The complex showed the same shifting of ::C = 0 band as in Cu(II)-buthidazole. However, there 1 for 1:1 still exists a pretty strong band at 1710 cm- ratio in nicke1(II) system. This showed that the complex is not so stable in Cu(II) system. 2. Interaction between Other Cations and Buthidazole Judging from the lack of shift of the C = 0 band (1720 cm"1 ), it showed no interaction between Ca and Na ions and buthidazole. It is apparent that Ca and Na ions do not form coordination complexes (Figure 20). 70 maoamofiausm Naomm NBoo Naoflz .6 .0 .n .M .Amuwaamm me. mmxmamfioo maonpflnuSQsHmumancofluflmcmuu mo mupommm commumcH .mH musmflm 71 7...: ..u._.......2£ GON— ooe ‘ 8.. 82 4‘ ’----. -O---‘---.C..- '-----O----.-----’------. :imm... uogssgmsuul 72 mHonpwnusnumuHuomEmIHomz «Homo mHonwflnusngmaomo mHONmoflsusm onmEoo mHONmpflnusnlmufluomEm: .6 .U .n .0 .mHonowcuonlmz cam sou mo muuommm UmumuwcH .om musmflm 73 7.... co. . £25.33; O— N— v- 0.. 0— O« on 1 J « J < . . d . . 4 . a < q 4 II. N w m m . K ...... . a B. . o . u u n m m a b P u p b .- + r L b p p p u b b ral 74 The buthidazole spectra in Al- and H-smectite systems seem to suggest protonation of the molecule. The C = 0 1 band (1720 cm-1) is shifted to around 1750 cm- in the HCl salt of buthidazole at pH 2.56, which is the pH of the H-smectite suspension (Figure 21). The 1555 cm-1 band at H-smectite may be due to the protonated buthi- l in HCl- dazole imine group(s), -$H+. The 1570 cm- buthidazole may be due to the salt of imine, —$H+Cl-. The C = 0 band shifting to the larger wavenumber in Al- and H-smectite is similar to the HCl salt of buthi- dazole. 3. Complexes of Organic Matter annguthidazole Due to the heterogeneity of soil organic matter, it is very difficult to obtain information from the IR spectra that reveals reactions between herbicides and soil organic matter. No significant modification of the IR spectra of buthidazole had been observed when it is desorbed from the Houghton muck. The water soluble organic matter also showed non-significant interaction with this herbicide as far as effects on the IR spectrum (Figure 22) are concerned. 4. Coordination Complexes of Tebuthiuron and Cu(II) Tebuthiuron (N-{S-(lrl-dimethylethyl)-1,3,4-thiadiazol- 2-yl}-N,N'-dimethylurea) is an analogous compound of buthidazole. It has been tested for the formation of coordination complexes with Cu(II). The 23C = 0 band at mHonpflzuznumufluomEmlm .w Homumaoumofinusm .6 Ammucme010m. mHonpwcuonlmufluomEmlad .o .EH.M smao. mHoneflnusnumufluomamuaa .n macameflsusm .m .mufiuomfim 75 sAHHHvad new I+m CH oaonpflnqu mo ouuommm poumumcH .HN musmflm 76 7.... co. . £25.33: 0 a D— N. v— 0— - . 0‘1 .- ---~----o---0 {I../iii nogssgmsuul 77 x05: counmsom Eoum mHonpfisusm UmQHommpIHmumz Hmuumz oficmmuo aflom monomuuxm nouns £UH3 pmxmameou mHonpfinusm mHonpflzusm Hmuamz oflcmmuo pmuomuuxm Hmpmz .U .0 .n .6 .xosz :ounmdom Sony Hmuumz owcmmuo Hwom £UH3 mHonpHnusm omuomnwucH mo muuommm pmumumcH .NN musmflm 78 7.5 cc. .. 22.22333 c— ON Om 4! d o a o_ N— V— 0— q 4 q 4 ‘------- 4 -- GUI uogssgmsueq 79 1676 cm“1 is shifted to 1634 cm"1 indicating complexing between Cu(II) and the oxygen atom of tebuthiuron (Figure 23). Penland et al. (1956) reported that urea formed several coordination complexes with Fe(III), Cr(III), Cu(II), Pt(II), and other metal ions through metal-oxygen interaction. The 22C = 0 band at 1683 cm"1 either increases for Pt(II) or decreases for Cu(II). Neither color change nor crystal formation occurred in the mixutre of Cu(II) and tebuthiuron. D. Catalytic Alteration of Buthidazole by Clays There are many reported catalytic reactions of organic matter caused by clay minerals (Faust 1940, Hauser and Leggett 1940, Ziechmann 1959, Mortland 1966, Fripiat et a1. 1966, Walker 1967, and Pinnavaia et a1. 1979). The IR spectra of the buthidazole extracted from the mixture of Cu(II)-smectite suspension showed some change. The sharp band at 1305 cm-1 disappeared. The band at 1485 cm-1 increased in intensity. For the same treatment in H- l l l smectite, the bands at 1342 cm- , 1305 cm- and 1280 cm” disappared (Figure 24). It is difficult to say what structural change resulting from any catalytic reaction(s) occurred because of the highly complicated spectrum of buthidazole. In Ca-smectite, the spectrum did not change at all. These results suggest that the protonation of buthidazole by the H-smectite and coordination by Cu(II) smectite may lead to alteration. 80 memEou cousflzusnmulsu .n consecusbme .m .Emum>m couswnusnme aw muuommm pmumumcH .mm musmfim 81 2’ Ts... . 35.5.53: coat ace ope. 1.; . } 919! uogssgmsuul 82 mHonpwnusm case .p muwuomamlm ha own>amumu .o mufluomEmIAHHvdu an Umnwamumo .n .5: «mm as :ofiuMficmnufi uanHI>D mo mHoNMUflsusm pmuwaouonm .m .coHuHmomEoomo mHonpflcusm mo poopoum mo muuowmm cmumumcH .vm musmflm 83 7.3 co... ..2........:.: o o. a. . v. e. a. on, ‘ V.) q I. ‘1 .vII'o .‘ ,. t 1.1 o . , C .v.. ll... .‘I.... I ont‘ 0.. . 7.161.. 9. .000 J I.» l I! 00.111 l 01149.7n0110'“ ‘..‘i'4nlllvldll m m » On 5.1.1-. 11.190513. 5 a. I-.. . uogssgmsunl 84 III. Photolysis of Buthidazole Results showed that buthidazole is labile to UV- light irradiation (Figure 25). The rate of photochemical decomposition was studied when the herbicide was exposed to light. The results indicated that the decomposition under irradiation of 254-um UV-light is a first order reaction (Figure 26): ——-— = - KC, or C = C e where C is the concentration of buthidazole, t is time of irradiation, K is a constant which is dependent on the intensity of the irradiation and other environmental fac— tors affecting the intensity. The absorbance of the irradiated solution does not increase upon standing for a long time. That means this photochemical reaction is not reversible, although other further chemical changes might be expected. Irradiation under 366-hm UV-light shows no concentration decrease of the buthidazole (Figure 25). Neither did the exposure under the regular light in the room for more than a year. Practically speaking, the whole spectrum of visible light does not cause the buthidazole solution to be significantly photolyzed. Crosby (1969) stated that most UV radiation that affects the pesticide decomposition is in the range 290 to 400 nm. However, this range of the spectrum does not cause the 85 .cowuflmomsoomo mHoncflsusm co :umcmam>mz >3 wo uomwmm one .mN musmflm 86 2...... .2...— 552.3... oo . . 0% CW GM 6... O.m c a O _ O a . n O No Q . / 332.33: < «d 6 6.22:5...— 3 t .3... can ‘ 222.22... .5 o /O L to D 4 0 ed .95 4 eggs... 6 6 2 9.22.3.2. 3 .. £2.62” 0.32.2.2. .5 c A 4 . N.— Ilq < - 5V q A.“ III. . . I /. u .1131: C i] o A v.— alozepmna )0 1:0qu aagielag JO aaueqiosqv 87 .AUOONV Es vmm um oHonpflnusm mo mfimwaouonm .mm musmflm Absorhance or Relative comm. oi Buthidazole 3.0 2.0 1.0: 38. .0 u D N 8 v88, L . 0 Cu Buthidazole a Ca Buthidazole 3;: A Buthidazole L L o 43 610 310 1100 Irradiation Time. Hours ' 89 photolysis of buthidazole. Apparently the lower wavelength UV-light is very specific for photodecomposi- tion of this compound. When buthidazole was irradiated at 254 nm in water solution, a very typical sharp IR band at 2250 cm.1 arose (Figure 24). Evidently, the photolytic compound(s) containing -N = C = 0 were formed. The Cu(II)-buthidazole I complex resists photolysis as mentioned before. The Cu(II) coordination must protect the breakdown of the N-C bond in the -N-C-N- structure. Krants and Laureni (1977, 1978) and Zeller et al. (1972) have reported L photolysis of thiadiazole, and identified many products formed in UV-light irradiation. But no success was achieved in cleavage of the thiodiazole ring of buthi- dazole. Munakta and Kuwahara (1969) stated that penta- chlorophenol (PCP) photodegraded through free radical formation and formed dimers, trimers or even polymers. The photolytic product(s) of buthidazole remains for further characterization. In terms of photodecomposition, Cu(II)-buthidazole mixture is resistant to irradiation when compared to those of Ca-buthidazole and buthidazole itself (Figure 25). The relative rates of calculated photodecomposition from Figure 26 are: Buthidazole/Ca-buthidazole/Cu-buthidazole = l/l.13/ 0.609. The rates of decomposition showed that the 90 combination of Cu(II) and buthidazole is different from Ca and buthidazole. The rate of Ca-buthidazole decomposi- tion is close to that of the pure buthidazole solution. These phenomena confirm the IR results that Cu(II) com- plexes with herbicide, and in so doing, affects the rate of photolysis. Photolytic products of buthidazole decomposition have not been identified as yet. The report of Mullison (1979) suggested that its photodecomposition and/or volatilization in water cause great loss when exposed to sunlight. Its half life is 20 to 25 days. A little structural modification of buthidazole under sunlight exposure which decreases the bioactivity, but is not sensitive to UV-visible or IR spectroscopic detection, is possible. In field application, a water film contain— ing the compound either on the soil or leaves may be very thin, therefore, the photolysis of buthidazole may become significant. Volatilization under such conditions is very great. IV. Bioactivity Study of Buthidazole Complexes The phytotoxicity of buthidazole upon corn in clays with different exchangeable cations showed no significant difference. The exchangeable Cu(II) not only did not decrease the apparent toxicity of buthidazole, but also retarded the germination of corn. The organic matter 91 in Houghton muck does not decrease the toxicity of buthidazole either. The different adsorption power of buthidazole in smectite and kaolinite did not make any difference in phytotoxic action on corn. Even compared to the unadsorbed buthidazole in the quartz sands, results showed no difference in phytotoxicity (Table 5). Chapman (1966) stated that the activity of atrazine decreased with increase of muck content in sands. As a rule of thumb, the organic matter content can be expected to increase with clay content of soils. Adams (1973) stated that it is quite difficult to establish the organic matter content of soil as the principal cause of pesticide behavior. Greenland (1971) considered that soil was not a mixture of separate particles of clay, organic matter and amorphous sesquioxides, but rather an intricate and complicated product of their varied properties. Buthidazole may bond with clays tightly under dry condition. Thus bioactivity of bonded herbicides may decrease or even lose phytotoxicity. In this experiment, the adsorbed buthidazole was assayed under wet conditions. It was loosely adsorbed through coordination formation as in Cu(II)-clays or other mechanism(s). The results suggest that the exchangeable cations in soil did not significantly affect the phytotoxicity under these experimental conditions. 92 .mocmHOMMHo OCMOHMflcmfim 0: 30cm Hmuuma mfimm mo mucoun.m .Amwmuomo .coomz. wuwcwaomxumouxnmo .Amcwfiows Gouda. OUfluomEmlmoumnmu .Acounmsom. x052": .ncmm unannouo t ammo.o NhH.o mm.a naoa.o hma.o wv.H ammo.o mmH.o N¢.H nohc.o eoH.o va.a namo.o ova.o NH.H bmmoé onH.o ov.H tho.o mha.o ~5.H ammo.o omH.o av.a ammo.o HvH.H ~m.oa memo + samum mama + xamum + uoom News + samum + boom Am. usmwm3 amp .m>< Am%xpnmfloz nos .m>¢ Emu oa Mlmo Ema H xnmu and OH mumo Sam A mlmu and o. 2 Sam A 2 see e. o Ema H O 0 «ucmfiummue .mafiom can mamHU uCOMOMMfiQ ca nusouw :Hou co maonpflnunm mo vommmm .m manna SUMMARY AND CONCLUSION The new herbicide, buthidazole, 3-{5-(1,l—dimethy1- ethyl)-l,3,4-thiadiazol-2-yl}-4-hydroxy-1-methy1-2-imi- dazolidinone, forms white needle-like crystals. Its unit cell dimensions are a = 11.73A, b = 11.10A, and c = 9.27A; a = B = y = 90° (Orthorhombic). The inter- action of buthidazole with clay minerals and soils can be summarized as following: (1) The buthidazole molecule can enter into the interlamellar space of the smectite. Exchangeable cations do not affect the d-spacing upon intercalation of buthi- dazole in smectite. (2) From the isothermic adsorption study, the Cu (II)-smectite and Cu(II)-kaolinite adsorb buthidazole according to the Langmuir model. The maximum amounts of adsoprtion of buthidazole on Cu(II)-smectite are 150 and 126 m moles/100g clay at 50°C and 20°C, respec- tively; those on Cu(II)-kaolinite are 29 and 21 m moles/ 100g clay at 50°C and 21.50C, respectively. Cu(II)-clays adsorb‘ more buthidazole than other non-transitional exchangeable cations because of their complexing character with buthidazole. In the Cu(II)-clays, the maximum 93 94 adsorption ratio of smectite to kaolinite is very close to the ratio of their CEC (around 7 to 1). In organic soil, the organic matter is predominately responsible for the adsorption of buthidazole, and exchangeable cations become less important. (3) Some results showed increase in adsorption with increase in temperature. Adsorption in wet systems does not significantly decrease the phytotoxicity. % (4) Infrared spectroscoPic studies prove the complex formation of buthidazole with transition metals, such as Cu(II), Ni(II), Co(II), and Fe(II). The complex formation ' takes place through the electron sharing of transition metals and oxygen in carboxyl group. The carboxyl C = 0 stretching band at 1720 cm“1 shifts to 1690 cm"1 after complex formation. The coordination ratio of Cu(II) to buthidazole is l to 1. Water molecules are suggested as other coordination members. No COpper and sulfur inter- action has been detected in IR spectra. Tebuthiuron (an analogous herbicide of buthidazole with carboxyl group) also forms complexes with Cu(II). No significant interaction of buthidazole with soil organic matter is found in Houghton muck, as far as changes in IR spectra is concerned. (5) The interaction of buthidazole in Al(III)- and H+-smectite is very similar. Protonation of the imine group was suggested as a possible mechanism. The 1720 cm—1 95 (c = 0) band shifts to 1750 cm‘l. (6) Some modification of the buthidazole structure has been revealed upon reaction with H-smectite and l, 1305 cm-1, and Cu(II)-smectite. Bands at 1342 cm- 1280 cm.1 disappeared when the material was adsorbed on H-smectite and the C = 0 stretching vibration lowered upon adsorption on Cu(II)-smectite. (7) Buthidazole is labile to UV-light. The photo- conversion of buthidazole by irradiation at 254 nm is a first order reaction. A wavelength of 366 nm did not cause significant decomposition of buthidazole. The photolytic product(s) typically have a very sharp IR band at 2250 cm-1, which is assigned as -N = C = 0. The Cu(II)-buthidazole complex formation reduces the rate of breakdown of the ring structure, however the Ca- buthidazole system does not. No significant photolysis of buthidazole takes place under normal room lighting. (8) Organic matter and exchangeable cations do not affect the bioactivity of buthidazole upon corn. This means there is no significant decrease of phytotoxicity of adsorbed buthidazole. ' In brief, the conclusion of this study is as follows: (a) Copper (II) and some other transition metals form complexes with buthidazole through :zC = 0 . . . M interaction. (b) The amounts of adsorption of buthidazole on clay minerals or soils depend mainly on the amount of (C) (d) 96 organic matter and exchangeable cations present (transition metal). Apparently, surface area is not a direct factor in transition-metal-clay and organic soils. Adsorbed buthidazole does not decrease the phyto- toxicity significantly in the environments provided in this study. Ultra violet light at 254 nm causes photolysis of buthidazole. The decomposed product(s) include -N = C = 0 structure. Complex formation of buthi- dazole can retard the photolysis. LI ST OF REFERENCES LIST OF REFERENCES Adams, R. 8. Jr. 1973. Factors influencing soil adsorption and bioactivity of pesticides. Residue Review. 47:1-54. Arnon, D. I. and D. R. Hoagland. 1940. Crop production in artificial culture solutions and in soils with special reference to factors influencing yields and absorption of inorganic nutrients. Soil Science. 50:463. Ashton, F. M. 1963. Fate of amitrole in soil. Weeds. 11:167-170. Bailey, G. W. and J. L. White. 1970. Factors influencing the adsorption, desorption, and movement of pesticides in soil. Residue Review. 32:29-92. Black, C. A. 1977. A "Comment from CAST" to Secretary Bergland. News from CAST. 4:66-67. Brindley, G. W. 1966. 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