MeOH System Research Articles

Sorptive Behavior of Sorgoleone in Ultisol in Two Solvent Systems and Determination of Its Lipophilicity

Sorgoleone (SGL) exuded by sorghum roots inhibits the development of some weeds. Due to its high hydrophobicity, it is expected that SGL presents low soil mobility and limited allelopathic activity in the field. This work aims to evaluate the sorptivity of sorgoleone in octanol-water and in soil under two solvent systems. The two solvent systems were methanol:water (60:40) (MeOH:H2O) and pure methanol (MeOH). These two solvent systems promote different conditions for SGL solubility. Treatments were arranged in a 2 × 6 factorial (solvent systems × equilibrium concentrations in the solution (EC)). For each solvent, the sorption was achieved by shaking 500 mg of soil with 10 ml of 0, 5, 10, 15, 25, 40, and 60 mg L−1 of SGL solution, during 24 h. After centrifugation, the supernatant was filtered and the SGL concentration was determined by high performance liquid chromatography (HPLC). Data of sorbed amount of SGL were submitted to variance analysis, using a hierarchic factorial model. The data of sorbed amount (x/m) and equilibrium concentration (C) were fitted to the linear (x/m = a + K d C) and to the Freundlich (x/m = K f C 1/n ) models. The isotherm obtained for the MeOH:H2O system presented linear shape, whereas for the MeOH system a two subsequent linear isotherm was fitted. Sorgoleone is a highly hydrophobic compound, presenting a log K ow of 6.1. The sorption of sorgoleone to the soil was very high. The organic environment stimulated the sorgoleone sorption to the soil.

Determination of sorption kinetic parameters using the relaxation‐dependent solubility model in the methanol vapor—Poly(methyl methacrylate) system

AbstractThe relaxation‐dependent solubility model was applied to simulate the experimentally observed sorption kinetic behavior of the PMMA–vapor MeOH system at 25°C, to obtain the main transport parameters. Application of the model in series of successive sorption kinetic runs covering small concentration intervals revealed certain trends in the concentration dependence of the diffusion coefficient of the system, not detectable by a previous simpler analysis of the data. Following excess free volume fill up, relaxation frequencies exhibit a weak exponential dependence on concentration. The functional dependence of the thermodynamic diffusivity on the concentration, deduced from the aforementioned simulation procedure, was tested and found to reproduce reasonably well the series of sorption kinetic runs covering considerably larger concentration intervals. In addition, this analysis indicates a strong dependence of the relaxation mechanism on the concentration interval. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2278–2288, 2006

The First Catalytic Asymmetric Allylation of Imines with the Tetraallylsilane—TBAF—MeOH System, Using the Chiral Bis‐π‐allylpalladium Complex.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Preparation of a sulfonated fused-silica capillary and its application in capillary electrophoresis and electrochromatography

In the present paper, two new methods, sol–gel and chemical bonding methods, were proposed for preparation of sulfonated fused-silica capillaries. In the sol–gel method, a fused-silica capillary was coated with the sol solution obtained by hydrolysis of 3-mercaptopropyltrimethoxysilane (MPTS) and tetramethoxysilane, and followed by age; while in the chemical bonding method, a capillary was chemically bonded directly with MPTS. Then, both the resulting capillaries were oxidized with an aqueous solution of hydrogen peroxide solution (H 2O 2) (30%, m/m) to obtain the sulfonated capillaries. The electroosmotic flow (EOF) for the sulfonated capillaries was found to remain almost constant within the studied pH range, and greater than that of the uncoated capillary. However, the coating efficiency of the capillary prepared by chemical bonding method was higher than that by sol–gel method, by comparing their magnitude of the EOF, the degree of disguise of the silanol and reproducibility of preparation procedure. The effects of the electrolyte’s concentration and the content of methanol (MeOH) on the EOF were also studied. Especially, the study of the apparent pH (pH ∗) on the EOF in a water–MeOH system was reported. Finally, capillary electrophoretic separation of seven organic acids was achieved within 6.5 min under optimal condition using the chemically bonded sulfonated capillary. Moreover, separation of four alkaloids on the sulfonated capillary was compared with that on uncoated capillary in different conditions. Ion-exchange mechanism was found to play a key role for separation of these four basic analytes on the sulfonated capillary.

Fabrication of poly(phosphoester) nerve guides by immersion precipitation and the control of porosity

Immersion precipitation was employed as a method for the fabrication of polymeric conduits from P(BHET-EOP/TC), a poly(phosphoester) with an ethylene terephthalate backbone, to be applied as guidance channels for nerve regeneration. Coatings of various porosities could be obtained by immersing mandrels coated with a solution of the polymer in chloroform into non-solvent immersion baths, followed by freeze or vacuum-drying. The porosity of the coatings decreased with an increase in polymer molecular weight, drying time before precipitation and concentration of polymer solution. The effects of these parameters can be rationalized by employing ternary phase diagrams, where porosity is directly related to the degree of phase separation available to the system before gelation occurs. To afford improved porosity control, a new system was developed which employed the contrasting phase-separation behavior of P(BHET-EOP/TC)/chloroform solution in methanol and water. As water is essentially a non-solvent for the polymer, the demixing boundary of the P(BHET-EOP/TC)–CHCl 3–H 2O system is located close to the polymer-solvent edge of the phase diagram, while that of the P(BHET-EOP/TC)–CHCl 3–MeOH system is located further away. A mixture of methanol and water allows the demixing boundary to be shifted to intermediate coordinates. By immersing P(BHET-EOP/TC) coatings in immersion baths containing different ratios of water and methanol, then gradually titrating the bath with methanol to a concentration of 70% (v/v) methanol, surface porosities ranging from 2 to 58% could be achieved.

Chemical modification of chitin and chitosan 2: preparation and water soluble property of N-acylated or N-alkylated partially deacetylated chitins

N-Acylated partially deacetylated chitin (DAC-88) derivatives were prepared via ring-opening reactions with various cyclic acid anhydrides in aqueous MeOH system. N-Alkylation of DAC-88 were also performed in aqueous MeOH with various aldehydes, monosaccharides, and disaccharides. The water solubility of N-acylated and N-alkylated chitosan derivatives at various pHs were studied.

Ions with a strong symmetrical H bond in the HCl−BuiOH system by IR spectroscopy data

Ion-molecular interactions in the HCl−BuiOH system with different compositions (from neat isobutyl alcohol to 37 mol.% HCl) were studied by Multiple Attenuated Total Reflectance (MATR) IR spectroscopy at 30 °C. Proton disolvates (Bui(H)O…H…O(H)Bui)+ with strong symmetrical H bonds are formed upon the addition of HCl to BuiOH. At high concentrations of HCl (C 0 HCl>33 mol.%), (Cl…H…Cl)− ions are formed along with (BuiOH)2H+. The spectra of positively and negatively charged proton disolvates were compared to those of similar ions in the HCl−PriOH and HCl−MeOH systems.

Mechanism of the reduction of molecular nitrogen to hydrazine by niobium (iii) hydroxide

The effect of the concentration of water on the rate of reduction of molecular nitrogen to hydrazine by niobium(iii) hydroxide in alkaline H2O−MeOH and D2O−MeOD mixtures was studied. In both cases, the reaction rate is maximum when [H2O]=4 mol L−1, and the inverse isotopic effect (KD/kH>1) is observed when [H2O]<20 mol L−1. Similar regularity was observed for the reaction of hydrogen elimination. It was found that HD is formed in the H2O−MeOH system in the presence of D2. The conclusion was made that the ratedetermining stage in hydrazine formation is the transfer of a hydride ion to the dinitrogen molecule coordinated to the binuclear NbIII center. A kinetic scheme satisfactorily explaining the effect of the concentration of water ([H2O]=1.5−49.0 mol L−1) on the reaction rate constant was proposed.

Reductive coupling of carbonyl compounds to pinacols by using SmI 2MeOH or SmI 2Ti(O iPr) 4MeOH systems

The coupling reaction of aromatic carbonyl compounds was performed with SmI 2 or SmI 2Ti(O i Pr) 4 in methanol. Meso isomer was mainly produced in the presence of Ti(O i Pr) 4.

A novel stereoselective and catalytic C [sbnd]C coupling reaction: acetylene dimerization accompanied by addition of iodine to yield ( E,E)-1,4-diiodobuta-1,3-diene in the Pt IV–I ––I 2–MeOH system

A new catalytic reaction-dimerization of acetylene accompanied by addition of iodine to yield (E,E)-1,4-diiodobuta-1,3-diene at 30°C in a methanolic solution of NaI, PtIV and I2 has been found; a plausible reaction mechanism involves intermediate formation of a cis-divinyl derivative of platinum(IV) through two subsequent triple bond iodoplatination steps followed by reductive elimination of the final product.

A novel ferrocenylalkylating reagent. Ferrocenylalkylation of imidazole and its derivatives

Reactions of α-(1-benzotriazolyl)ethylferrocene (1) with 1,2,4-triazole, imidazole, benzimidazole, and edenine have been studied in the MeOH−HCl, MeOH, and AcOH systems. Compound 1 is a novel ferrocenylalkylating reagent which, unlike α-hydroxyalkylferrocenes, is capable of alkylating imidazole, benzimidazole (even in the absence of an acid catalyst), and adenine (regioselectively at the N(3) position). The antitumor activity discovered for ferrocenylalkylazoles of the type 1 may be attributed to the ability of such compounds to ferrocenylalkylate nucleic bases.

Use of high‐field 119Sn NMR and the pairwise additivity model for chemical shifts in the identification of complexes in the SnBr4–KSCN–MeOH system

AbstractThe interaction of SnBr4 and KSCN in methanol solution has been studied by 119Sn NMR at 149 MHz and −30°C. Evidence was obtained for the existence of both the cis and trans isomeric forms of SnBr4·2MeOH. A pairwise additivity model for chemical shifts was used to explain the observed peaks and many of the possible species, SnBrn(NCS)4‐n·2MeOH. [SnBrn(NCS)5‐n·MeOH]‐ and [SnBrn(NCS)6‐n2−], (n=0–4), and their somecies, forms were identified and shown to exist simultaneously in solution in complex equilibria. In some cases 119Sn–14N coupling was observed. The implications for possible synthesis of these types of compounds and the necessity for measurement at high field are discussed.

Impact of biological matrix and isolation methods on detectability and interlaboratory variations of TLC Rf-values in systematic toxicological analysis.

The retention behavior of eight basic and neutral drugs, extracted from plasma, blood, and liver by five different methods (XAD-2, Extrelut, Elut-X, Elut-C18, chloroform) and developed in three chromatographic systems [MeOH, Me OH:BuOH:NaBr, CHCl3:MeOH (KOH)] was observed in parallel in two laboratories. The corrected Rf-values were compared with reference data from a data base with data for pure drugs. The biological matrix and/or the extraction severely lowered the precision and, to a lesser extent, the accuracy of the Rf-values as compared to pure drug data and to reference Rf-values. The intra- and interlaboratory variation was smallest in the MeOH system and largest in the CHCl3:MeOH (KOH) system. The observed irreproducibility is caused by the biological matrix (extraction has a large negative impact on the potentials of TLC in identification procedures). Precision and accuracy of extracted drugs were independent of the biological matrix and on the extraction method used.

Studies on the mechanism of catechol oxidation with the CuCl—Pyridine—MeOH System

Studies on the mechanism of catechol oxidation with the CuCl—Pyridine—MeOH System

Conformation et réactivité de dérivés [4.n.0] bicycliques à jonction trans—XXVI: Méthanolyse du tosylate de phényl-4a bicyclo(4.2.0]-octyle-3a trans et du tosylate de phényl-4e bicyclo[4.2.0]octyle-3e trans en l'absence et en présence de MeONa. mise en évidence d'un intérmediaire ion phénonium

The structure of the reaction products and the rate constants for methanolysis of 4a-phenyl 3a-tosyloxy bicyclo[4.2.0]octane trans 1 and 4e-phenyl 3e-tosyloxy bicyclo(4.2.0]octane trans 2 in different MeO−/MeOH systems, suggest that these reactions do not involve a phenyl-assisted, but an ion-pairing process. The secondary cation formed in a first slow step leads to the phenyl-bridged ion by a phenyl shift. Owing to steric hindrance, solvent attack is not observed on the covalent compound 1, and a solvent change causes the mechanism to change: phenyl participation which has been previously established in CF 3CH 2OH, a convenient solvent for this assisted process, is not observed in MeOH. So in a more nucleophilic medium when solvent assistance is inhibited, unlike β phenylalkyl primary derivatives, a secondary β phenyl substrate may not react by phenyl participation but may present a nearly limiting behavior.