Zirconium tetra-n-butylate modified with different organic acids: Hydrolysis and polymerization of the products

In this work, (a) complexation reaction of zirconium tetra-n-butylate, Zr(OBu ⁿ )₄, with MAc and different organic acids, (b) the hydrolysis reaction of modified Zr species, and (c) the polymerization reaction of complex products are studied. Zr(OBu ⁿ )₄ was reacted with different mole ratios of methacrylic acid (MAc) at room temperature and the maximum combination ratio was found to be 1:2 [Zr(OBu ⁿ )₄:MAc] by FT-IR. The modification of zirconium tetra-n-butylate with the acid mixtures [methacrylic acid-acetic acid (MeCOOH), methacrylic acid-propionic acid (EtCOOH), methacrylic acid-butyric acid (PrCOOH)] was made for a combination ratio of 1:1:1 [MAc:RCOOH:Zr(OBu ⁿ )₄; R: Me, Et, Pr] and the products were characterized by¹H-NMR, FT-IR, and UV spectroscopies. Following their synthesis, hydrolysis of the complexes with various amounts of water and polymerization with benzoyl peroxide were realized. The hydrolysis and polymerization products of the complexes were studied by Karl-Fischer coulometric titration and thermal analysis, respectively. Methyl ethyl ketone(MEK) and chloroform were chosen as solvents.     

Preparation of methyl 11,14,17-eicosatrienoate-8,8,9,9-d 4 and methyl 8,11,14,17-eicosatetraenoate-8,9-d 2

Methyl 11,14,17-eicosatrienoate-8,8,9,9-d ₄ was obtained by Wittig coupling of 3,6-nonadienyltriphenylphosphonium iodide with methyl 11-oxoundecanoate-8,8,9,9-d ₄. For the synthesis of the phosphonium salt, 2-pentynol was converted to 1-bromo-2-pentyne with triphenylphosphine dibromide. Grignard coupling of 1-bromo-2-pentyne with 3-butynol in the presence of cuprous chloride gave 3,6-nonadiynol. The latter was hydrogenated in the presence of P-2 nickel catalyst to yield 3,6-nonadienol. The dienol was convertedvia the bromide and iodide to the phosphonium salt. The aldehyde ester was prepared starting with the coupling of 7-bromoheptanoic acid and 3-butynol with lithium amide in liquid ammonia. The hydroxyalkynoic acid obtained was converted to the methyl ester and the hydroxy group was converted to the tetrahydropyranyloxy group. Subsequent deuteration of the methyl 11-(2-tetrahydropyranyloxy)-8-undecynoate with deuterium gas andtris-(triphenylphosphine)chlorohodium gave the corresponding tetradeuterated product. The tetrahydropyranyl group was removed and the methyl 11-hydroxy-undecanoate-8,8,9,9-d ₄ was oxidized to the aldehyde ester with pyridinium chlorochromate. Methyl 8,11,14,17-eicosatetraenoate-8,9-d ₂ was obtained by a similar sequence of reactions. The methyl 11-oxo-8-undecenoate-8,9-d ₂ required for the Wittig coupling was obtained by Lindlar deuteration of the protected alkynoic ester to methyl 11-(2-tetrahydropyranyloxy)-8-undecenoate-8,9d ₂. The unsaturated hydroxy ester was oxidized to the aldehyde ester by periodinane with negligible isomerization. The allcis isomers were isolated by silver resin chromatography. The mention of firm names or trade products does not imply that they are endorsed or recommended by the U.S. Department of Agriculture over other firms or similar products not mentioned.     

Biodiesel production by the transesterification of cottonseed oil by solid acid catalysts

Methyl esters (biodiesel) were produced by the transesterification of cottonseed oil with methanol in the presence of solid acids as heterogeneous catalysts. The solid acids were prepared by mounting H₂SO₄ on TiO₂ · nH₂O and Zr(OH)₄, respectively, followed by calcining at 823K. TiO₂-SO₄ ²⁻ and ZrO₂-SO₄ ²⁻ showed high activity for the transesterification. The yield of methyl esters was over 90% under the conditions of 230°C, methanol/oil mole ratio of 12:1, reaction time 8 h and catalyst amount (catalyst/oil) of 2% (w). The solid acid catalysts showed more better adaptability than solid base catalysts when the oil has high acidity. IR spectral analysis of absorbed pyridine on the samples showed that there were Lewis and Br?nsted acid sites on the catalysts. Translated from The Chinese Journal of Process Engineering, 2006, 6(4): 571–575 [译自: 过程工程学报]     

Synthesis of tetrazole from α, β—Unsaturated carbonyl fatty acid

Methyl 4-oxo-trans-2-octadecenoate (II), when treated with excess hydrazoic acid in the presence of BF₃-etherate, produced 66% methyl 5-aza-nonadec-trans-2-enoate (4,5-d)-tetrazole (III), 10% methyl 5-aza-nonadec-4-oxo-trans-2-enoate (IV) and 7% pentadecamide (V). Individual products were characterized by spectral and elemental methods.     

Phospholipases A<Subscript>1</Subscript> from <Emphasis Type="Italic">Armillaria ostoyae</Emphasis> Provide Insight into the Substrate Recognition of α/β-Hydrolase Fold Enzymes

Four enzymes with phospholipase A₁ (PLA₁) activity were purified from the fruiting bodies of the basidiomycete Armillaria ostoyae. The enzymes (PLA₁-1, -2, -3 and -4) showed similar isoelectric points (4.3, 3.9, 4.0 and 4.0) and apparent molecular masses in the range of 35–47 kDa. Mass spectrometric analyses of proteolytic fragments revealed sequences homologous to α/β-hydrolase fold enzymes. The enzymes share one conserved region with fungal phospholipases B and the active site sequence with bacterial esterases and PLA₁s. PLA₁-1 cleaves phospholipids and lysophospholipids with an optimum activity at pH 5.3. In contrast, PLA₁-2, -3 and -4 are characterized by broad pH optima in the slightly acidic to neutral range and are additionally capable of hydrolyzing mono- and diglycerides as well as fatty acid methyl esters. All enzymes favor glycerol-based lipids with a single medium-sized fatty acid moiety in the sn-1 position but show reduced activity towards the corresponding 1,2-diacyl derivatives with bulky long-chain or inflexible saturated fatty acid moieties in the sn-2 position. The enzymes prefer zwitterionic phospholipid substrates and are unable to hydrolyze triglycerides. From the selectivity of these broad-spectrum α/β-hydrolase fold enzymes towards the different classes of their substrates a regiospecific steric hindrance and a head group recognition are concluded.     

Products of the Reaction Between Alcohols and Phosphorus Pentoxide. III. Identification by Infrared Spectrophotometry

The various compounds obtained by the reaction P₄O₁₀ + 4ROH (where R represents hydrocarbon radicals of various length and structure) were identified by infrared spectrophotometry of the fractions separated by column chromatography. The identification was made possible by a comparison between the relative values of the integrated absorption for the P = O, P-O-P, P-O-C and O-H bands with those of known standards. For the reaction of phosphorus pentoxide with ethanol, the compounds formed were found to be: mono-, di- and triethyl phosphate, mono-, (1, 2) di- and triethyl-pyrophosphate; (1, 3) di- and (1, 2, 3) triethyl triphosphate; mono- and diethyl trimetaphosphate. With other alcohols, only homologs of these compounds were found, but always fewer compounds. Uncertainty between possible isomers was resolved by identification of their acid hydrolysis products.     

Preparation and properties ofgem-dichlorocyclopropane derivatives of long-chain fatty esters

Methyl oleate (18∶1) and linoleate (18∶2) were readily transformed to the correspondinggem-dichlorocyclopropane derivatives in high yield, using triethylbenzylammonium chloride as the phase-transfer catalyst in the presence of aqueous NaOH and CHCl₃. Reaction of dichlorocarbene with methyl 12-hydroxystearate furnished methyl 12-chlorostearate (49%) and 12-O-formylstearate (19%). The hydroxy group in methyl ricinoleate was protected (O-tetrahydropyran-2′-yl) prior to dichlorocyclopropanation of the ethylenic bond. Removal of the protecting group allowed the hydroxy group to be converted to a chloride,O-acetyl, azido orO-formyl function. Treatment of methyl ricinoleate with thionyl chloride, followed by the reaction with dichlorocarbene gave the corresponding 12-chloro-dichlorocyclopropane derivative. The dichlorocyclopropane derivative of oleic acid was transformed to a C₁₉ allenic fatty acid when treated witht-butyl lithium. However, the remaining dichlorocyclopropane derivatives, containing an additional functional group in the alkyl chain, failed to yield the corresponding allenic derivatives. All derivatives were characterized by a combination of spectroscopic and chromatographic techniques, including infrared,¹H nuclear magnetic resonance (NMR), and¹³C NMR spectroscopy.     

Initiation system effects in the cationic copolymerization of tetrahydrofuran (THF)

Summary Macromonomeric peroxy initiator, poly tetrahydrofuran (poly-THF=inimer) were synthesized via cationic polymerization of THF by the mono- (t-BuBP) and tetra-bromo methyl benzoyl peroxides (BDBP)/ZnCl₂ initiating system. The macromonomers were characterized by ¹H-NMR, IR, and GPC techniques. Methyl methacrylate (MMA) polymerization initiated by poly-THF inimers at 80°C and different times in bulk gave crosslinked poly-THF-b-polymethyl methacrylate block copolymers. Swelling ratios of the crosslinked block copolymers obtained by taking in same amounts of poly-THF inimer and MMA monomer in CHCl₃ were decreased versus time. It was compared the results obtained from t-BuBP-, BDBP-ZnCl₂ initiating systems with t-BuBP-, BDBP-AgSbF₆ initiating systems for THF monomer. Poly(THF-b-MMA) crosslinked block copolymers containing undecomposed peroxide groups initiated the thermal polymerization of styrene, S, were used to obtain poly(THF-b-MM_A-b-S) crosslinked multicomponent copolymers at 90°C. The crosslinked multi component copolymers were investigated sol-gel analysis and swelling ratios in CHCl₃. "Active" poly(THF-b-MM_A) having peroxygen group were used in the free radical coupling reaction of poly butadien (Poly Bd). Poly(THF-b-MM_A)-polybutadien crosslinked blend soluble graft copolymers were obtained. Received: 31 July 2001/Revised version: 16 June 2002/ Accepted: 5 July 2002     

The alpha-sulfonation of alkyl palmitates and stearates

Methyl, ethyl, and isopropyl esters of palmitic or stearic acid werea-sulfonated directly by the dropwise addition of a 2.4 molar ratio of liquid sulfur trioxide to the ester, with or without solvent, at 0C. Scission of the ester apparently takes place during sulfonation. Yield of the ester RCH-(SO₃Na)CO₂R was increased, and yield of by-product disodium salt was decreased by reesterification with methyl, ethyl, or isopropyl alcohol prior to neutralization. Direct sulfonation of the ester by sulfur trioxide, without solvent, gave 70-80% yields, increased 10% by the presence of a small amount of CCl₄ as the solvent (1 ml/g of ester). Mixtures of thea-sulfo ester and the disodium salt can be analyzed by infrared spectra. 1 Presented at the AOCS Meeting in Philadelphia, October 1966 2 E. Utiliz. Res. Dev. Div., ARS, USDA.     

α-Substituierte Phosphonate. XXXIV. Zur Veresterung und N-Formylierung von α-Aminomethan-bisphosphonsäuren mit Orthoameisensäuretriethylester

α-Substituted Phosphonates. XXXIV. Esterification and N-Formylation of α-Aminomethane-bisphosphonic Acids with Triethylorthoformate In contrast to simple mono- and bisphosphonic acids esterification of dialkylaminomethanebisphosphonic acids with orthoformate (OAE) proceeds very slowly. Monoalkyl and monoarylaminomethanebisphosphonic acids, respectively react with OAE in constrast to analogous hydroxy compounds more readily primarily by formylating the N-atom and then esterification to formyl aminomethane bisphosphonictetraesters 10 . Acetaminomethanephosphonic acid ( 12 ) reacts without N-formylation, while the aminomethanebisphosphonic acid ( 14 ) reacted to give a mixture of mono- and bis-formylated products 15 and 16 . By acidic hydrolysis of 10 the ester- and formylgroups are splitt off, while the ester group can selectively be removed by reaction with Me₃SiBr/H₂O. – As shown by ¹H-, ¹³C- and ³¹P-n.m.r. spectroscopy the phosphorylated formamides 10 exists in two rotameres, the ratio depending on the solvent. The n.m.r. signals could be correlated to E-resp. Z-form undoubtedly by using shift-agents or the benzene-diluting technique. A rotational barrier of 22,8 kcal for 10c could be calculated.     

Enantioselective formation of an α, β-epoxy alcohol by reaction of methyl 13(S)-hydroperoxy-9(Z), 11(E)-octadecadienoate with titanium isopropoxide

Methyl 11(R), 12(R)-epoxy-13(S)-hydroxy-9(Z)-octadecenoate (threo isomer) was generated from linoleic acid by the sequential action of an enzyme and two chemical reagents. Linoleic acid was treated with lipoxygenase to yield its corresponding hydroperoxide [13(S)-hydroperoxy-9(Z), 11(E)-octadecadienoic acid]. After methylation with CH₂N₂, the hydroperoxide was treated with titanium (IV) isopropoxide [Ti(O-i-Pr)₄] at 5°C for 1 h. The products were separated by normal-phase high-performance liquid chromatography and characterized with gas chromatography-mass spectrometry, infrared spectroscopy, and nuclear magnetic resonance spectroscopy. Approximately 30% of the product was methyl 13(S)-hydroxy-9(Z), 11(E)-octadecadienoate. Over 60% of the isolated product was methyl 11(R), 12(R)-epoxy-13(S)-hydroxy-9(Z)-octadecenoate. After quenching Ti(O-i-Pr)₄ with water, the spent catalyst could be removed from the fatty products by partitioning between CH₂Cl₂ and water. These results demonstrate that Ti(O-i-Pr)₄ selectively promotes the formation of an α-epoxide with the threo configuration. It was critically important to start with dry methyl 13(S)-hydroperoxy-9(Z),11(E)-octadecadienoate because the presence of small amounts of water in the reaction medium resulted in the complete hydrolysis of epoxy alcohol to trihydroxy products.     

On the acidity of liquid and solid acid catalysts. Part 3. Esterification of benzoic and mesitoic acids

Methyl esters of benzoic and mesitoic acid have been prepared with high yields (>98 wt%) from the corresponding carboxylic acids + methanol in aprotic solvents over samples of H₂SO₄/SiO₂ at 60°C. The results show a high catalytic efficiency of the solids but also suggest an acid strength comparable to that observed in concentrated aqueous H₂SO₄ (range >90 wt%) when the acid requirements for the esterification of analogous compounds in aqueous acid solutions are taken into account. Indeed, different reacting species, i.e., ArC(OH) ₂ ⁺ from benzoic acid and 2,4,6‐triMe‐ArC=O⁺ from mesitoic acid are involved in the esterification, but the mesitoyl cation can be formed and esterified in the acidity ranges between 92 and 98 wt% H₂SO₄. This revised version was published online in July 2006 with corrections to the Cover Date.     

Preparation of deuterated methyl 6,9,12-octadecatrienoates and methyl 6,9,12,15-octadecatetraenoates

Methyl 6,9,12-octadecatrienoate-15,15,16,16-d ₄ was obtained by Wittig coupling between 6,6,7,7-tetradeutero-3-nonenyltriphenylphosphonium iodide, 8, and the aldehyde ester, methyl 9-oxo-6-nonenoate. Methyl 6-oxohexanoate, obtained by ozonolysis of cyclohexene, was coupled in a Wittig reaction with [2-(1,3-dioxan-2-yl)ethyl]triphenylphosphonium bromide to give methyl 8-dioxanyl-6-octenoate. This compound was transacetalized to methyl 9,9-dimethoxy-6-nonenoate, which was then hydrolyzed to the aldehyde ester. For the preparation of compound 8, the tetrahydropyranyl ether of 2-pentynol was deuterated with deuterium gas and tris-(triphenylphosphine)chlororhodium. The tetradeuterated tetrahydropyranyl ether was converted to the bromide with triphenylphosphine dibromide, and the bromide was coupled with 3-butynol by means of lithium amide in liquid ammonia to give 3-nonynol-6,6,7,7-d ₄. Hydrogenation over Lindlar's catalyst converted the deuterated alkynol to 3-nonenol-6,6,7,7-d ₄. This deuterated alkenol was converted to the bromide with triphenylphosphine dibromide, then to the iodide with sodium iodide in acetone, and finally to 8 with triphenylphosphine in acetonitrile. Methyl 6,9,12,15-octadecatetraenoate-12,13,15,16-d ₄ was obtained by Wittig coupling between methyl 9-oxo-6-nonenoate and 3,4,6,7-tetradeutero-3,6-nonadienyltriphenylphosphonium iodide, 15. For the preparation of compound 15, the bromide obtained from the reaction of 2-pentynol with triphenylphosphine dibromide was coupled with 3-butynol with lithium amide in liquid ammonia. The resulting 3,6-nonadiynol was deuterated with deuterium gas in the presence of P-2 nickel, and the resultant deuterated nonadienol was converted to 15 through the bromide and iodide. The final products were separated from isomers formed during the synthetic sequences by silver resin chromatography.     

Poly[(maleic acid)-co-styrene]–platinum complex; a catalyst for the hydrogenation of methyl formate

Coordinate bonds form between oxygen and platinum atoms in crosslinked poly[(maleic acid)-co-styrene]–platinum complex according to FTIR and XPS measurements. The complex is demonstrated to be an active and selective catalyst for the hydrogenation of methyl formate under mild conditions (25°C, 1 atm H₂). Methyl formate can be converted selectively to methanol in 82·6% yield within 6h at a COOH/Pt mole ratio of 17·85 in the complex with n-propanol as the solvent. The catalyst exhibits high stability, with turnover number (mol of methyl formate converted/mol of platinum) of the catalyst reaching 1064 within 48 h.     

Model study on the aqueous-phase hydrodechlorination of clopyralid on noble metal catalysts

The aqueous-phase catalytic hydrodechlorination (HDC) of the herbicide clopyralid was studied for the first time. The reaction was carried out on platinum- (Pt), palladium- (Pd) and gold- (Au) based mono- and bimetallic catalysts at 25 °C and atmospheric pressure using a batch reactor. Clopyralid (3,6-dichloropyridine-2-carboxylic acid) is a systemic herbicide from the chemical class of pyridine compounds, which has a high potential to contaminate water sources. The hydrodechlorination of clopyralid (C₆H₃NO₂Cl₂) proceeds step-wise to the monochlorinated intermediates 3-chloropyridine-2-carboxylic acid and 6-chloropyridine-2-carboxylic acid (C₆H₄NO₂Cl) and to the dechlorinated intermediate picolinic acid (C₆H₅NO₂). The dechlorination is followed by hydrogenation with formation of the harmless end product pipecolinic acid (C₆H₁₀NO₂). With different alumina supported mono- and bimetallic catalysts a complete dechlorination and hydrogenation of clopyralid could be achieved. Pd and PdAu catalysts showed the highest activity for the dechlorination steps whereas the Pt and PtAu catalysts are most active in the complete conversion of clopyralid, i.e. combined dechlorination and hydrogenation. Summarizing, HDC is an easily applicable way to remove clopyralid from water.     

Assignment of13C nuclear magnetic resonance signals in fatty compounds with allylic hydroxy groups

¹³C Nuclear magnetic resonance (NMR) signals in several fatty compounds with allylic mono- and dihydroxy groups were assigned by comparing compounds with and without other functional groups (allylic hydroxy, carboxylic acid, respectively, methyl ester at C₁). The simple¹³C NMR spectra of hydroxylated compounds derived from symmetrical alkenes are particularly useful in making assignments. The compounds whose signals were partially assigned are 8-hydroxy-9(E)-octadecenoic acid, 11-hydroxy-9(E)-octadecenoic acid, 8, 11-dihydroxy-9(E)-octadecenoic acid, 9(E)-octadecen-8-ol, and 9(E)-octadecene-8, 11-diol. The present evaluation can be used for assigning signals in other fatty compounds.     

Solvent extraction and separation of rare earths from chloride media using α-aminophosphonic acid extractant HEHAMP

Solvent extraction and separation of rare earths (REs: La ~ Lu, plus Y and Sc) by a novel synthesized extractant, (2-ethylhexylamino)methyl phosphonic acid mono-2-ethylhexyl ester (HEHAMP, abbreviated as H₂A₂), were investigated in chloride medium. The favorable separation factors (SFs) between adjacent heavy REs suggested that HEHAMP has a better separation performance than P507. The extracted complex of trivalent REs was determined to be REClH₂A₄ by the slope analysis method. Thermodynamic parameters (ΔH, ΔG, and ΔS) of Lu were calculated as 7.47 kJ mol^?1, ?6.05 kJ mol^?1, and 45.4 J mol^?1 K^?1 at 298.15 K, respectively, which indicate that the extraction reaction of Lu is an endothermic process. The loading capacity of 30% (v/v) HEHAMP toward Lu(III), Yb(III), and Y(III) was about 15.17 g Lu₂O₃/L, 14.46 g Yb₂O₃/L, and 12.64 g Y₂O₃/L, respectively. HCl is the most efficient stripping acid, and 92% of the loaded Yb(III) can be stripped by one-stage stripping with 2 mol/L HCl.     

Synthesis of pentavalent imidovanadium complexes and their catalyses for the polymerization of ethylene and propylene

Imidovanadium complexes with cyclopentadienyl (Cp) ligands—(Cp)V(?NC₆H₄Me‐4)Cl₂ (1), (Cp)V(?N^tBu)Cl₂ (2), and (^tBuCp)V(?N^tBu)Cl₂ (3; ^tBuCp = tert‐butylcyclopentadienyl)—were synthesized through the reaction of imidovanadium trichloride with (trimethylsilyl)cyclopentadiene derivatives. The molecular structure of 3 was determined by X‐ray crystallography. The monocyclopentadienyl complex 1 exhibited moderate activity in combination with methylaluminoxane [MAO; 10.3 kg of polyethylene (mol of V)^?1 h^?1 atm^?1], whereas similar complexes with bulky ^tBu groups, 2 and 3, were less active. (2‐Methyl‐8‐quinolinolato)imidovanadium complexes, V(?NR)(O ?N)Cl₂ (R = C₆H₃ⁱPr₂‐2,6 (4) or n‐hexyl (5), O ?N = 2‐methyl‐8‐quinolinolato), were obtained from the reaction of imidovanadium trichloride with 2‐methyl‐8‐quinolinol. Upon activation with modified MAO, complex 4 showed moderate activities for the polymerization of ethylene at room temperature. The complex 5/MAO system also exhibited moderate activity at 0°C. The polyethylenes obtained by these complexes had considerably high melting points, which indicated the formation of linear polyethylene. Moreover, the 5/dried MAO system showed propylene polymerization activities and produced polymers with considerably high molecular weights and narrow molecular weight distributions. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1008–1015, 2005     

Electrochemical acetoxylation of 2-methylnaphthalene

The oxidation of 2-methylnaphthalene in the solution of lithium acetate in glacial acetic acid has been investigated. It has been found that, within the range of potentials 1.10–1.25 V vs saturated mercury acetate electrode in glacial acetic acid, the oxidation process results in mono- and diacetates of 2-methylnaphthalene formation. The values of E_τ/4 for 2-methylnaphthalene, 1-acetate-2-methylnaphthyl and 1,4-diacetate-2-methylnaphthyl oxidation have been determined as 1.09, 1.05 and 1.13 V, respectively. The degree of 2-methylnaphthalene conversion to monoacetate reaches its maximum value at 1.25 V which is 32.8%.     

Zirconium tetra-n-butylate modified with different organic acids: Hydrolysis and polymerization of the products

In this work, (a) complexation reaction of zirconium tetra-n-butylate, Zr(OBu ⁿ )₄, with MAc and different organic acids, (b) the hydrolysis reaction of modified Zr species, and (c) the polymerization reaction of complex products are studied. Zr(OBu ⁿ )₄ was reacted with different mole ratios of methacrylic acid (MAc) at room temperature and the maximum combination ratio was found to be 1:2 [Zr(OBu ⁿ )₄:MAc] by FT-IR. The modification of zirconium tetra-n-butylate with the acid mixtures [methacrylic acid-acetic acid (MeCOOH), methacrylic acid-propionic acid (EtCOOH), methacrylic acid-butyric acid (PrCOOH)] was made for a combination ratio of 1:1:1 [MAc:RCOOH:Zr(OBu ⁿ )₄; R: Me, Et, Pr] and the products were characterized by¹H-NMR, FT-IR, and UV spectroscopies. Following their synthesis, hydrolysis of the complexes with various amounts of water and polymerization with benzoyl peroxide were realized. The hydrolysis and polymerization products of the complexes were studied by Karl-Fischer coulometric titration and thermal analysis, respectively. Methyl ethyl ketone(MEK) and chloroform were chosen as solvents.