Anhydrous Organic Solvents Research Articles

Thermokinetic Studies of Porphyrin Complexation in Non-Aqueous Solutions by Heat Conduction Microcalorimetry

Abstract Porphyrins are known as unique ligands forming some of the most stable complexes with various metal ions. In this work the thermokinetic investigations of complex formation of tetraphenylporphyrins with copper(II) acetate were carried out in two anhydrous organic solvents: acetic acid and DMF at 25C. Measurements were performed in a heat conduction microcalorimeter [7] adapted for non-aqueous solvents. Total heat effects and thermokinetics were determined. The results were discussed together with spectrophotometric data. Taking into account the high stability of metalloporphyrin complexes, the heat of their formation is rather small (in the case of acetic acid ΔQ=32.71.2 kJ mol−1, for DMF ΔQ=26.21.3 kJ mol−1). Such result can suggest that: 1) the stability of complexes is influenced strongly by an entropy factor, 2) the complexation involves breaking of the NH-bond in the porphyrin coordination centre, accompanied by high consumption of energy.

A Reinvestigation of Nitration of Phenols with Metal Nitrates under Non-Aqueous and Aprotic Conditions

Nitration of phenol and various 4-substituted phenols with Cu(NO3)2.3H2O, Cu(NO3)2.3H2O/SiO2, 9H2O and Cr(NO3)2. 9H2O in different anhydrous organic solvents are investigated. High selectivity ratio of para vs ortho isomers has been observed. Mono- and dinitro compounds from phenol and 4-substituted phenols by choosing the proper solvents and reaction conditions, are also obtained with high selectivity in excellent yields. Rate enhancement for mononitration of phenols in the presence of LiClO4 with Cu(NO3)2.3H2O is observed.

Organic Phase Enzyme Electrodes Based on Organohydrogel

A dimethylformamide−polyhydroxyl cellulose organohydrogel has been prepared, and its applications for enzyme immobilization in construction of organic phase biosensors have been exploited. With horseradish peroxidase, tyrosinase, and bilirubin oxidase immobilized in the organohydrogel, enzyme electrodes can be operated in various situations, including aqueous buffer, oil/water mixtures, and anhydrous organic solvents, and even in dimethylformamide, to determine analytes of different solubilities, e.g., organic peroxides, phenolic compounds and bilirubin. Biosensing has no restrictions in terms of measuring media and solubilities of analytes.

Environ-friendly approaches to densely functionalized β-lactams

A convenient approach to densely functionalized α-allyl-β-lactams has been developed using organometallic reagents and α-keto-β-lactams. Indium mediated Barbier reaction in aqueous media proceeded with a higher level of diastereoselectivity and chemical yield than zinc mediated Barbier reaction in anhydrous organic solvents.

Effect of organic solvents on enantioselectivity of protease catalysis

The protease-catalyzed transesterifications between N-trifluoroacetyl-DL-phenylalanine 2,2,2-trifluoroethyl ester and 1-propanol were studied in a variety of anhydrous organic solvents at 30 degrees C. The protease preparations lyophilized from phosphate buffer solutions (pH 8.0) were used as catalysts. The organic solvent affected both rate of reaction and enantioselectivity differently. Proteases such as Aspergillus oryzae protease, subtilisin Carlsberg, and subtilisin BPN' always preferred the L-enantiomer in both hydrophilic and hydrophobic solvents, indicating no inversion of the L-specificity in hydrophobic solvents such as toluene. However, enantioselectivity was rather poor, with E (enantiomeric ratio) values not exceeding even one order of magnitude except for acetonitrile. There was a weak inverse correlation between E values of subtilisin Carlsberg and solvent hydrophobicity (logP). Acetonitrile was a preferable solvent in terms of both rate of reaction and enantioselectivity (E= 15 to 25) for processing L-amino acid derivatives in organic media. Organic solvents generally have potential advantages of processing D-amino acid derivatives. (c) 1997 John Wiley & Sons, Inc.

The effect of organic solvent properties on a catalase enzyme sensor for monitoring hydrogen peroxide in nonaqueous solutions

AbstractA catalase based biosensor for determining hydrogen peroxide in organic solvents, operating directly in nonaqueous solutions, was prepared, characterized (using water saturated chloroform as solvent) and applied in comparative tests using four different anhydrous organic solvents in order to determine their effect on biosensor sensitivity and thus on enzymatic activity in different organic solvents. Results are discussed in terms of log P and dielectric constant (DEC) values of the solvents considered.

Low temperature organic phase biocatalysis using cold-adapted lipase from psychrotrophic Pseudomonas P38

Lipase produced by a psychrotroph, Pseudomonas fluorescens P38, was found to catalyse the synthesis of butyl caprylate in n-heptane at low temperatures. The optimum yield of ester synthesis was 75% at 20 °C with an organic phase water concentration of 0.25% ( v v ). The results are discussed in terms of the structural flexibility of psychrotroph-derived lipase and the activity of this enzyme within a nearly anhydrous organic solvent phase.

Lipase-Assisted Synthesis of β-Gal-(1→3)-GalNAc

Regiospecific ethanolysis of anomeric acetate (1, 2, and 3) and benzoylation on 6-OH (7) by lipase in anhydrous organic solvents will be described. The derivatives are applied to the synthesis of β-Gal-(1→3)-GalNAc.

SelectiveN-Sulfation of Glucosamine Derivatives using Phenyl Chlorosulfate in Non-Aqueous Solvent

Abstract The selective N-sulfation of 2-amino-2-deoxy-D-glucopyranose derivatives having unprotected hydroxyl groups with phenyl chlorosulfate and triethylamine in anhydrous organic solvent followed by addition of aqueous sodium bicarbonate affords high yields of the 2-deoxy-2-sulfoamino-D-glucopyranose products.

Long-term preservation of antibody activity and binding to polyester cloth by dessication

During 70 days of dessicated storage at 32°C over CaSO4, rabbit IgG and rabbit antihorseradish peroxidase antibody remained adsorbed onto polyester cloth, retaining full immunoactivity both as an antibody and an antigen. After dessicated storage, the adsorbed antibody could not be released from the polyester cloth by agitated washing in any of the following anhydrous water-mixable organic solvents: methanol, glacial acetic acid, dimethyl sulfoxide, dimethylformamide, or 1,4-dioxane.

Visible spectrum of dinitrogen trioxide in aqueous solution

The visible absorption spectrum of N2O3 has been measured by stopped-flow mixing of solutions of NaNO2 and HNO3. It has a maximum at 630 nm, Iµ= 29.3 dm3 mol–1 cm–1. The spectrum is similar to that reported for solutions of N2O3 in anhydrous organic solvents at low temperatures. Comparison with the blue species observed for solutions of NaNO2 in moderately concentrated HClO4 and HNO3 shows that although the spectra are very similar there must be an additional species present in these very acidic media, possibly N2O3H+.

Enzymatic polytransesterification of aromatic diols in organic solvents

Enzymatic polytransesterification of aromatic diols was carried out in anhydrous organic solvents. The protease from Bacillus licheniformis catalyzed the polytransesterification of a diester of glutaric acid with aromatic diols such as benzenedimethanol. Gel permeation chromatography (GPC) provided Mw values of 400–1400 daltons for the aromatic polyesters. Bis(2,2,2-trifluoroethyl) glutarate and 1,4-benzenedimethanol were used as model compounds to study the influence of aromaticity, solvent, and water content.

Effects of acyl groups and ethanol ratios on lipase-catalyzed regioselective deacylation in peracylated methyl glycopyranosides

Regioselective ethanolysis of peracylated methyl β, α-D-glucopyranoside and methyl α-D-mannopyranoside in anhydrous organic solvent (n-hexane/EtOH = 99/1) could afford 6-OH derivatives exclusively by Candida rugosa lipase (CRL). No 4 → 6 acyl migration was observed in such an anhydrous solvent system. Substrates with propanoyl groups were more reactive than with acetyl groups on CRL-catalyzed reactions.

Polysilylated Coenzyme A for a High-Yielding Preparation of Very Lipophilic Acyl Coenzymes A in Anhydrous Organic Solvents

Polysilylated Coenzyme A for a High-Yielding Preparation of Very Lipophilic Acyl Coenzymes A in Anhydrous Organic Solvents

Enzymatic Synthesis of Various Aromatic Polyesters in Anhydrous Organic Solvents

Lipases and proteases from various sources were tested in aromatic polyester synthesis in organic solvents. A commercial protease from Bacillus licheniformis efficiently catalyzed the transesterifica-tion of a diester of terephthalic acid and 1,4-butanediol in anhydrous tetrahydrofuran (THF). This protease was used as a catalyst in the synthesis of aromatic polyesters in THF. Oligomers with average molecular weights from 400 to 1000 daltons were obtained using various diols and aromatic diesters.

Kinetic analysis of the mechanism for subtilisin in essentially anhydrous organic solvents

Steady-state kinetic analysis has been used to confirm the catalytic mechanism of lyophilized subtilisin suspended in a variety of organic solvents. Specifically, this article demonstrates that partial reactions can occur between subtilisin and ester substrates in organic solvents. Partitioning of common intermediates between competing acceptors at a constant ratio of products has also been described. The decomposition of a common intermediate formed from different substrates at the same rate is also further evidence of an acyl-enzyme mechanism for subtilisin suspended in anhydrous solvents. Partitioning of a common intermediate to give two products at a constant total rate, and saturation kinetics at varying substrate concentrations, complete a kinetic investigation of the enzyme mechanism. All the data generated support the formation of a stable acyl enzyme during the transesterification reaction catalzyed by subtilisin in the solvents used.

The hydration of proteins in nearly anhydrous organic solvent suspensions.

Water sorption isotherms at 27 degrees C have been measured for lysozyme and chymotrypsin in suspensions of toluene, di(n-butyl) ether, n-propanol, and a solution of 1M n-propanol in benzene. Sorption isotherms for the different suspensions are compared by converting solvent water content to the thermodynamic activity of water in each solvent. The sorption behavior is also compared to that for the two proteins hydrated from the vapor phase. At low water activities, all sorption isotherms are similar when compared on the basis of water activity. However, at higher activities, water sorption by the proteins in the organic suspensions is suppressed relative to the sorption of water vapor. The greatest suppression is observed for n-propanol, which suggests that the suppression may be due to a competition for water-binding sites on the protein by the organic solvent. Sorption isotherms at low water activities have also been predicted using a thermodynamic model in which it is assumed that water binds selectively to the ionizable residues on the surface of the protein. A comparison of predicted and measured sorption isotherms shows that the model can provide reasonable estimates of water sorption in nonpolar or moderately polar organic solvent suspensions at low levels of hydration.

Determination of equilibrium and individual rate constants for subtilisin‐catalyzed transesterification in anhydrous environments

We report here the first determinations of individual rate constants and equilibrium constants for enzymatic reactions in essentially anhydrous organic solvents. Using the added nucleophile method we have measured the effect of changing solvent on the binding and catalytic steps for subtilisin-catalyzed transesterification of N-protected amino acid esters. The detailed information generated indicates that once the substrate has bound to the enzyme, the catalytic machinery can work at rates equivalent to those in water. The decreased overall rates for subtilisin suspended in anhydrous solvents are merely the result of extremely high values for K(s), in most cases, coupled with low concentrations of nucleophile ( approximately 1.0M in organic solvents, and 55M in water). The method described, which is generally applicable, and straightforward experimentally, will, we believe, enable a clearer understanding of how changing solvent can predictably affect the activity and specificity of the enzyme.

Activity of Thiolsubtilisin in Organic Solvents

AbstractIn this paper, we compare the activities of subtilisin and thiolsubtilisin in anhydrous organic solvents and in mixtures of water and miscible organic media. The information obtained indicates that changing from one organic solvent to another does not significantly affect the stability of the transition state for the reaction. Thus, since the transition state is charged, it is likely that the active site of the enzyme is electrostatically protected from bulk solvent. Further, since the activities of subtilisin and thiolsubtilisin are different in the solvents used, it is clear that the active site serine is a catalytically important residue in both water and organic solvents.

Role of diffusion in nonaqueous enzymology. 1. Theory

Using a set of standard equations, we have calculated the role of internal and external mass transfer in limiting the rate of enzyme-catalysed reactions in anhydrous organic solvents and supercritical fluids. We have shown that enzyme particles suspended in anhydrous organic solvents will be subject to increasing diffusional limitation as the enzyme activity and particle size increase. Using particle dimensions, as measured by scanning electron microscopy, we have prepared a series of graphs that will enable investigators to determine whether their combination of particle size and activity will result in internal or external diffusional limitations. We have shown that supercritical fluids can be expected to enhance the activity of enzymes in nonaqueous environments as a result of the high diffusivity of the bulk solvent. The plots also clearly indicate that enzyme particles in supercritical fluids require nearly two orders of magnitude less agitation than those suspended in conventional solvents in order to overcome any external mass transfer limitations.