Showing papers on "Solvent published in 1972"

4,4'-Isopropylidene-bis(3- and 4-phenyleneoxyphthalic anhydride)

Abstract: Aryloxy dianhydrides are prepared from the hydrolysis of the reaction product of a nitro-substituted phenyl dinitrile with a metal salt of a dihydroxy aryl compound in the presence of a dipolar aprotic solvent.

Preferential and absolute interactions of solvent components with proteins in mixed solvent systems

Abstract: An equation is derived relating total and preferential interactions of solvent components with macromolecules in a three-component system. Application of this equation to literature data shows that binding of non-polar solvents to proteins parallels the unfolding of the latter. This observation is discussed in terms of local inter-residue and residue-solvent interactions.

Laser Photolysis Studies on the Formation of Solvated Ion Radicals in the Pyrene–N,N-Dimethylaniline System in Various Solvents

Abstract: Formation of solvated ion radicals in the pyrene-N,N-dimethylaniline (DMA) system (which is a typical one showing heteroexcimer (HE) fluorescence) in various solvents has been studied by means of the laser photolysis and transient photoconductivity as well as transient absorption measurements Ion radical formation due to the encounter collision between an excited pyrene and DMA in moderately as well as in strongly polar solvents has been established This result is quite important in explaining the experimentally observed relation between the solvent dependent HE fluorescence quantum yield and decay time

Some studies of benzenoid-quinonoid resonance. Part 2.—The effect of solvent polarity on the structure and properties of merocyanine dyes

Abstract: The SCF π-electron theory with bond length optimization, described in part 1, has been used to calculate the effects of solvent polarity on the structure and spectroscopic properties of a simple merocyanine dye. The calculations predict a minimum in energy and oscillator strength of the first absorption band over the range of solvent parameters used, but these extrema should not occur at the same solvent compositions. The measured u.-v. spectra can be interpreted from these results, and the n.m.r. chemical shifts, which change with solvent, can be correlated with calculated net atom charges.

Surface active N-acylglutamate: I. Preparation of long chain N-acylglutamic acid

Abstract: Long chain N-acylglutamic acid was prepared in a high yield by a reaction of glutamic acid with fatty acid chloride in a mixed solvent of water and a water miscible organic solvent such as acetone, methyl ethyl ketone, dioxane, tetrahydrofuran,t-butyl alcohol or cyclohexanone. In this reaction the composition of the mixed solvent influenced the yield of N-acylated glutamic acid and the best yield was obtained when the reaction was carried out in the mixed solvent comprising 30–60% v/v of the organic solvent. Long chain N-acylaspartic acid was also obtained in a high yield by the same method. As the other method to obtain N-lauroyl-D L-glutamic acid, it was examined that N-acyl-α-aminoglutarodinitrile which was obtained by a reaction of α-aminoglutarodinitrile with fatty acid chloride was hydrolyzed with an aqueous alkaline solution. The salts of long chain N-acylglutamic acid are known as the surface active agents that react mildly on the human skin.

Separation of organic phosphorus compounds and their metal complexes from organic nitriles in the hydrocyanation of olefins

Abstract: A PROCESS FOR SEPARATING AN ORGANIC PHOSPHORUS COMPOUND SUCH AS A PHOSPHITE OR PHOSPHOKITE OR A ZEROVALENT NICKEL COMPLEX OF THE ORGANIC PHOSPHORUS COMPOUND FROM A PRODUCT FLUID CONTAINING ORGANIC NITRILES PRODUCED BY HYDROCYANATING AN ETHYLENICALLY UNSATURATED ORGANIC MONO-NITRILE SUCH AS 3-PENTENENITRILE THROUGH EXTRACTION OF THE PRODUCT FLUID WITH A PARAFFIN OR CYCLOPARAFFIN HYDROCARBON SOLVENT AT A TEMPERATURE OF ABOUT 0*C. TO ABOUT 100*C. TO PRODUCE A MULTIPHASE MIXTURE WHEREIN THE ORGANIC PHOSPHORUS COMPOUNDS AND THEIR METAL COMPLEXES ARE CONTAINED PREDOMINANTLY IN THE HYDROCARBON PHASE AND THE ORGANIC MONO-AND DINITRILES AND DEGRADATION PRODUCTS ARE CONTAINED IN A SEPARATE PHASE.

The Melting Temperature of Thermally Reversible Gel. I. Poly(vinyl chloride)–Organic Solvent Gels

Abstract: The Melting Temperature of Thermally Reversible Gel. I. Poly(vinyl chloride)–Organic Solvent Gels

The measurement of nanogram amounts of acetylcholine in tissues by pyrolysis gas chromatography.

Abstract: — A method previously described for measuring ACh in biological effluents has been simplified and extended for use with tissues. The tissue is homogenized in acetonitrile containing propionylcholine as the internal standard and after centrifugation the acetonitrile is removed by shaking with toluene. To the aqueous solution is added a solution of KI-I2 to precipitate the quaternary compounds. The precipitate is dissolved in aqueous acetonitrile and then drawn through a small column of ion-exchange resin to convert the periodides of the quaternary compounds to chlorides which are then simultaneously pyrolysed and gas chromatographed. On the column the pyrolytic product of choline has a slower retention time than that of acetylcholine; under these circumstances the choline present in tissues does not obscure the measurement of acetylcholine. Specificity was demonstrated by several procedures including mass spectroscopy. The method can measure 25 ng (171 pmoles) of acetylcholine in extracts of brain, simply, and with high reproducibility. With the usual gas chromatograph, 16 samples can be run in a working day. The content of acetylcholine in rat brain was 26.4 nmol/g or almost precisely the values found with other gas chromatographic methods. The pyrolytic method was shown to be applicable to the detection of biologically interesting substances other than choline esters, including betaine, carnitine and the non- quaternary compound, ź-aminobutyric acid, which is readily converted to a volatile compound (probably its methyl ester) when pyrolysed in the presence of tetramethylammonium hydroxide. Of additional general interest is the demonstration of the advantages of acetonitrile as a solvent for extracting water-soluble compounds from tissues.

Process for preparing sterols from tall oil pitch

Abstract: 1. A PROCESS FOR PREPARING STEROLS FROM PLANT SOURCES COMPRISING THE STEPS OF: (A) DISSOLVING A PLANT-DERIVED STEROL SOURCE IN A SOLVENT MIXTURE COMPRISING AN ALCOHOL CONTAINING FROM ABOUT 1 TO ABOUT 6 CARBON ATMS AND A LIQUID HYDROCARBON, AND ADDING WATER IN AN AMOUNT FROM ABOUT 0.5% TO ABOUT 10% BY WEIGHT OF ALCOHOL AND ALLOWING THE PHASES TO SEPARATE; (B) SAPONIFYING THE STEROL ESTERS OBTAINED FROM THE HYDROCARBON PHASE OF STEP (A) WITH AN ALKALI METAL BASE AT A TEMPERATURE FROM ABOUT 90*F. TO ABOUT 500*F. IN A LOWER ALCOHOL SOLVENT; AND (C) DISSOLVING THE STEROLS OBTAINED FROM STEP (B) IN A POLAR, APROTIC ORGANIC SOLVENT IN WHICH SOAPS ARE INSOLUBLE, DISCARDING SAID SOAPS, AND RECOVERING THE STEROLS FROM THE SOLVENT.

Significance of Molecular Alignment and Orbital Steering in Mechanisms for Enzymatic Catalysis

Abstract: Calculations of the energy required to form misaligned transition states in the confines of a solvent cage indicate that many reactions could be very considerably catalysed by precise alignment (orbital steering) in enzyme active sites.

Recovering anhydrous acrylic acid

Abstract: Acrylic acid practically devoid of water, acrolein, formaldehyde and acetic acid is obtained at particularly low cost by countercurrent scrubbing and quenching of the reaction gas formed in the catalytic oxidation of propylene and/or acrolein with a high-boiling, extremely hydrophobic solvent followed by processing of the extract.

Photodegradation of urethane model systems

Abstract: The photo-oxidation products of ethyl N-phenyl-carbamate (EPC) were identified as ethyl o-aminobenzoate, ethyl p-aminobenzoate, aniline, water, carbon dioxide, azo compounds, and other colored material. The ethylaminobenzoates, formed by intramolecular rearrangement of EPC, were precursors of the azo and colored products. Diethyl 4,4′-azobenzenedicarboxylate was produced by the ultraviolet irradiation of the precursor, ethyl p-aminobenzoate, in the presence of oxygen. Benzophenone and anthraquinone, as the triplet donors, sensitized the photo-oxidation of EPC. Quantum yields of photolysis of EPC were measured. The photorearrangement reaction was inhibited by the polar solvent (ethanol). The presence of metal ions and phenyl isocyanate in EPC showed no effect on the oxygen consumption rate.

Substitution at saturated carbon. Part XIV. Solvent effects on the free energies of ions, ion-pairs, non-electrolytes, and transition states in some SN and SE reactions

Abstract: Standard free energies of transfer from methanol to various other solvents are reported for dissociated species R4N++ X–(20–30 solvents), ion pairs R4NX (20–30 solvents), t-butyl chloride (20 solvents), t-butyl bromide (10 solvents), tetramethyltin (15 solvents), tetraethyltin (15 solvents), and tetraethyl-lead (10 solvents). A dissection on solvent influences on ΔG‡ into initial-state and transition-state contributions has been accomplished for the decomposition of t-butyl chloride (18 solvents), the decomposition of t-butyl bromide (10 solvents), the Menschutkin reaction of NN-dimethylaniline with methyl iodide (3 solvents), and the iododemetallation of tetra-alkyl-leads (8 solvents).A comparison of solvent effects on the free energies of ion pairs with solvent effects on the free energies of transition states suggests that transition states carry the following units of charge separation: [ButCl]‡ 0·70 (polar solvents), [graphic omitted] 0·5 (non-polar solvents); [ButBr]‡ 0·68 (polar solvents); [p-NO2·C6H4·CH2Cl–Me3N]‡ 0·35. Charge separation in the [R4Pb–l2]‡ transition states is probably rather higher than in the transition state of the Menschutkin reaction.

Structure and permeability of porous films of poly(hydroxy ethyl methacrylate)

Abstract: Porous films of poly(hydroxy ethyl methacrylate) have been made by photo-polymerisation of solutions of the monomer. The permeability of homogeneous films depends on the cross-link density and the concentration and composition of the polymerisation solvent. A membrane of minimum water permeability, in which the transport mechanism is principally diffusion, results from a cross-link concentration of ∼9.4 mol-% and a monomer concentration of ∼75% in an aqueous ethylene glycol solvent (20% ethylene glycol). More porous (macroporous) films were prepared by first cooling the solution such that the solvent freezes and the monomer occupies the interstices between the solvent crystals. After polymerisation and removal of the solvent, a porous structure results. The rate of freezing, the profile of the thermal gradient, and the solvent and crosslinker concentrations control the permeability of this film. Slow cooling gives random pores (K ≃6 × 10−15 cm2), but rapid, directional cooling from one face gives oriented pores with K ≃10−12 cm2. A 6-order change in K results from varying the monomer concentration from 40 to 85% in a 4:1 water: ethylene glycol solvent, and a 3-order change from increasing the ethylene glycol content of the solvent from 0 to 40% at a fixed monomer concentration.

The Photochemical Reaction of α-Diketones

Abstract: The relative photochemical reactivity of α-diketones, in particular, 9,10-phenanthraquinone, 1,2-naphthoquinone, acenaphthoquinone, benzil, 4,4′-dimethylbenzil, 2,4,6-trimethylbenzil, 2,5,2′,5′-tetramethylbenzil, 2,3,5,6-tetramethylbenzil, 2,4,6,2′,4′,6′-hexamethylbenzil, phenylglyoxal, 2,5-dimethylphenylglyoxal, and 2,4,6-trimethylphenylglyoxal was investigated in hydrogen donating solvents. Type of the product and relative reactivity differ widely according to the structure of α-dike tones. Whereas 9,10-phenanthraquinone gives 1,4-adduct (V) in a hydrogen donating solvent (THF), 2,5,2′,5′-tetramethylbenzil gives 2-hydroxy-2-(2′,5′-dimethylphenyl)indanone (VII) via intramolecular hydrogen abstraction in nearly quantitative yield. No photochemical reaction of 2,4,6-trimethylbenzil or 2,3,5,6-tetramethylbenzil could be observed in the same solvent even under a long irradiation.

Konformationsanalyse, I. Abhängigkeit der syn‐1.3‐diaxialen Wechselwirkung von der Art des Substituenten und vom Lösungsmittel Untersuchungen der Konformations‐Gleichgewichte von D‐Idopyranose‐Derivaten

Abstract: Die syn-1.3-diaxiale Wechselwirkung zweier OAc-Gruppen ist verschwindend klein gegenuber der von zwei OCH3-Gruppen. In unpolaren Losungsmitteln sind syn-1.3-diaxiale Wechselwirkung zweier OCH3-Gruppen und der anomere Effekt am grosten. In Chloroform treten Wasserstoffbruckenbeziehungen zur anomeren OCH3-Gruppe auf, die den anomeren Effekt und in der α-Reihe die 1.3-diaxiale Wechselwirkung schwachen. Das die Lage der Konformeren-Gleichgewichte bestimmende Wechselspiel von syn-1.3-diaxialer Wechselwirkung, anomerem Effekt und Einflus des Losungsmittels wird an verschieden substituierten D-Idopyranose-Derivaten der α- und β-Reihe diskutiert. Conformational Analysis, I. Dependency of syn-1.3-Diaxial Interaction on the Kind of Substituents and on the Solvent Studies on the Conformational Equilibria of D-Idopyranose Derivatives The syn-1.3-diaxial interaction of two OAc-groups is very small compared to that of two OMe-groups. syn-1.3-Diaxial interaction of two OMe-groups and anomeric effect are maximal in unpolar solvents. In chloroform hydrogen bridge linkages with the anomeric OMe-group are formed which weaken the anomeric effect and in the α-series the syn-1.3-diaxial interaction. The site of conformational equilibria which is determined by the variable influence of syn-1.3-diaxial interaction, anomeric effect, and solvent is discussed for differently substituted D-idopyranose derivatives of the α- and β-series.

Solution Properties of Synthetic Polypeptides. XI. Solvent Effect on Helix–Coil Transition in Polypeptides

Abstract: A number of synthetic polypeptides are known to undergo “inverse” thermal helix–coil transitions in solvent mixtures containing an “active” solvent such as dichloroacetic acid (DCA). A statistical mechanical theory of the effects of the active component on the transition is developed here on the assumption that the active solvent exists in the form of a dimer and that the dimerized molecules react with pairs of CO and NH groups of randomly coiled peptide units. Expressions are derived for the equilibrium constant, u, of helix formation and the cooperativity parameter, σ, and they are used to analyze data obtained for poly(γ-benzyl-L-glutamate) and poly(β-benzyl-L-aspartate) in mixtures of DCA and ethylene dichloride as functions of temperature and solvent composition. The values of the transition parameters so determined make it possible to understand not only why and how the observed values of transition enthalphy ΔH and cooperativity parameter σ depend on temperature and solvent composition, but also the general features of inverse transitions in quantitative terms. An important conclusion is that σ is profoundly affected by the binding of the active solvent on the polypeptide chain.

Heats of solution and dilution for polyethylene oxide in several solvents

Abstract: The Tian-Calvet microcalorimeter, as modified by Maron and Filisko, has been used to measure the heats of solution and dilution of a sample of polyethylene oxide (PEO) of M2 = ca. 6000 in chloroform, methylene chloride, and water. By applying the Maron theory to these measurements, it was found from the organic solvent data that the heat of fusion of the PEO sample is 57.1 cal/g polymer, independent of the solution concentration or the solvent used. However, the solution behavior in water was different because PEO in organic solvents exists as a random coil, whereas in water its conformation is helical. By combining the water and organic solvent data, it can be shown that conversion of the random coils to the helix involves the evolution of 39.3 cal of heat per gram of polymer. This heat evolution accounts, in all probability, for the solubility of PEO in water.