Chemical toughening of epoxies. I. Structural modification of epoxy resins by reaction with hydroxy-terminated poly (butadiene-co-acrylonitrile)

In an attempt to toughen the epoxy resin matrix for fiber-reinforced composite applications, a chemical modification procedure of a commercially available bisphenol-A-based epoxy resin using reactive liquid rubber HTBN [hydroxy-terminated poly(butadiene-co-acrylonitrile)] and TDI (tolylene diisocyanate) is described. The progress of the reaction and the structural changes during modification process are studied using IR spectroscopy, viscosity data, and chemical analysis (epoxy value determination). The studies support the proposition that TDI acts as a coupling agent between the epoxy and HTBN, forming a urethane linkage with the former and an oxazolidone ring with the latter. The chemical reactions that possibly take place during the modification are discussed.

Chemical toughening of epoxies. I. Structural modification of epoxy resins by reaction with hydroxy-terminated poly(butadiene-co-acrylonitrile)

In an attempt to toughen the epoxy resin matrix for fiber-reinforced composite applications, a chemical modification procedure of a commercially available bisphenol-A-based epoxy resin using reactive liquid rubber HTBN [hydroxy-terminated poly(butadiene-co-acrylonitrile)] and TDI (tolylene diisocyanate) is described. The progress of the reaction and the structural changes during modification process are studied using IR spectroscopy, viscosity data, and chemical analysis (epoxy value determination). The studies support the proposition that TDI acts as a coupling agent between the epoxy and HTBN, forming a urethane linkage with the former and an oxazolidone ring with the latter. The chemical reactions that possibly take place during the modification are discussed.

Irreversible inactivation of 3-hydroxy-3-methylglutaryl-CoA reductase by H2O2

A concentration-dependent inactivation of 3-hydroxy-3-methyl-glutaryl-CoA (HMG-CoA) reductase was found on reincubation of rat liver microsomal preparations with H2O2 and at lower concentrations in the presence of KCN which inhibited the contaminating catalase. The inactivation was not affected in the presence quenchers of hydroxyl radicals and singlet oxygen and was also obtained when H2O2 was added during the reaction. HMG-CoA, but not NADPH, partially protected the enzyme from H2O2-inactivation. Even at high concentration DTT was unable to reverse this inactivation. The soluble 50 kDa-enzyme was similarly inactivated by H2O2, and the tryptic-digest of the inactivated protein indicated the presence of a disulfide-containing peptide. The results support the view that H2O2 by directly acting on the catalytic domain possibly converts an active thiol group to an inaccessible disulfide and irreversibly HMG-CoA reductase.

One pot synthesis of polycyclic oxygen aromatics. Part IV reaction of THP ether of 2-bromomethyl phenols

Reaction of 2-bromomethyl-1-(2′-tetrahydropyranyloxy) benzene 3a with tetrachlorocatechol(TCC) in acetone in presence of anhydrous K2CO3 resulted in the formation of diastereomeric products to which cis- & trans- 6-chloro-8-hydroxy-8-(2-oxopropyl)spiro[9H-benzo[a]xanthen- 9,2′(1′H) benzofuran]-7(8H)-one (7a & 8a) structures were assigned, along with tetrachlorocatechol ethers (5a & 6a). Similar reaction of 3a with tetrabromocatechol(TBC) gave the expected monobromo compounds 7d & 8d along with the ethers 5d & 6d. When the reaction was repeated with substrates 3b–c with TCC/TBC in ketonic solvents(acetone/methyl ethyl ketone), the corresponding compounds 5b–c to 8b–c, 5e–f to 6e–f, 7e–g & 8e–h were obtained. A suitable explanation has been given for the formation of acetonyl compound 6 in this reaction.

Construction of energy-level diagram of oriented benzene using connectivity information obtained by modified z-cosy experiment

Experiments involving selective perturbation of a transition yield information about the directly connected transitions, which in turn yield information for deriving the parameters of the spin Hamiltonian of oriented molecules. Problems involved with selective perturbation are removed by the use of a two-dimensional experiment, namely, the modified Z-COSY-experiment, The use of this experiment is demonstrated for obtaining the connectivity information and for determining the parameters of the spin Hamiltonian of oriented benzene, a strongly coupled six-spin system

Physical characterization of the organic nonlinear optical crystal � 3-methoxy 4-hydroxy benzaldehyde

We highlight our recent experimental work on an efficient molecular nonlinear optical crystal, 3-methoxy 4-hydroxy benzaldehyde (MHBA). Optical quality single crystals of MHBA were grown from mixtures of solvents and from melt. The overall absorption and transparency window were improved by growing them in a mixture of chloroform and acetone. The grown crystals were characterized for their optical transmission, mechanical hardness and laser damage. We have observed a strong correlation between mechanical properties and laser induced damage.

Preparation of a soluble 58kDa-3-hydroxy-3-methylglutaryl CoA reductase from liver microsomes and its inhibition by ethoxysilatrane, a hypocholesterolemic compound

On repeated thawing at room temperature of frozen preparations of heavy microsomes from rat livers, HMGCoA reductase activity was solubilized due to limited proteolysis. This soluble enzyme was partially purified by fractionation with ammonium sulfate and filtration on Sephacryl S-200 column. The active enzyme was coeluted with a major 92 kDa-protein and was identified as a 58kDa-protein after separation by SDS-PAGE and immunoblotting. Ethoxysilatrane, a hypocholesterolemic compound, which decreased the liver-microsomal activity of HMGCoA reductase on intra-peritonial treatment of animals, showed little effect on the enzyme activity with isolated microsomes or the 50kDa-soluble enzyme when added in the assay. But it was able to inhibit the activity of the soluble 58kDa-enzyme in a concentration-dependent, reversible manner. Cholesterol and an oxycholesterol were without effect whereas chlorophenoxyisobutyrate and ubiquinone showed small inhibition under these conditions. The extra region that links the active site domain (50kDa protein) to the membrane, present in the 58kDa-protein appears to be involved in mediating the inhibition by silatrane.

Solubilities of Benzene Derivatives in Supercritical Carbon Dioxide

The solubilities of benzene derivatives in supercritical carbon dioxide was determined by the saturation method over the pressure range (9.5 to 14.5) MPa. The solubilities were determined at (308 and 313) K for 1-chloro-2,4-dinitrobenzene and (308, 318, and 328) K for m-dinitrobenzene. At 308K, the solubility (in mole fraction) of 1-chloro-2,4-dinitrobenzene varied from (2.83 to 5.88).10(-3) while the solubility of m-dinitrobenzene increased from (2.05 to 5.54).10(-3) as the pressure increased from (9.5 to 14.5) MPa. However, the solubilities of both compounds decreased with increasing temperature. Models based on the solubility parameter and semiempirical models such as the Mendez-Santiago-Teja model, the Gordillo model, and the association model, were used to correlate the experimental solubility data for the benzene derivatives.

Synthesis and reactivity of chiral tellurium azomethines: Pseudopolymorphism of [o-((((1S,2R)-2-hydroxy-2-phenyl-1-methylethyl)amino)methinyl)phenyl] tellurium(IV) bromide

A range of novel chiral tellurium compounds having an azomethine functional group in the position ortho to tellurium has been synthesized by the reaction of the tellurium-containing aldehydes bis(o-formylphenyl) telluride (1) and o-(butyltelluro)benzaldehyde (4) with chiral amines (R)-(+)-(1-pheylethylamine) and (1R,2S)-(-)-norephedrine, respectively. The precursor aldehydes were prepared by using a reported procedure with slight but advantageous modifications. During the preparation of o-(butyltelluro)benzaldehyde, interesting side products, namely bis(o-formylphenyl) ditelluride ethylene acetal 5, bis(o-formylphenyl) tritelluride (6), and bis(o-formylphenyl) ditelluride (7) were isolated in moderate yields. The ditelluride 7 has been characterized by single-crystal X-ray diffraction studies. The liquid Schiff bases 10 and 11 were further characterized by derivatizing with liquid bromine. The title compound was obtained in excellent yield by reacting the Schiff base 11 with elemental bromine. Detailed NMR studies indicated the presence of a rigid environment for the hydroxyl group. Single-crystal X-ray determinations of the crystals obtained from the different batches indicated. the presence of the two pseudopolymorphic forms 13a and 13b, respectively. In the case of 13a there is one molecule of CH3CN as solvent of crystallization, whereas in 13b half a molecule of CH3CN per molecule of the title compound lies along the 2-fold axis. In 13a the hydroxyl hydrogen is hydrogen-bonded to the nitrogen of the solvent molecule, whereas in 13b it is hydrogen-bonded to the bromine of the neighboring molecule.

Crystal and molecular structure of synthetic cholesterol compounds vitamin D3-analogues (I) 24(S)-hydroxy coprastan-3-one & (II) 24(R)-hydroxy coprastan-3-one

The title compound I (24-(S)-Hydroxy Coprastan-3-one) crystallises in orthorhombic space group P2(1)2(1)2(1) with Z = 4. The unit cell dimensions are a = 6.701(2)Angstrom, b = 11.506(8)Angstrom, c = 32.183(4)Angstrom, V = 2481(2)Angstrom (3), D-cal = 1.077 Mg/m(3). The tide compound II (24-(R)-Hydroxy Coprastan-3-one) crystallises in orthorhombic space group P212121 with two molecules per assymetric unit and with Z = 8. The Unit cell dimensions are a = 10.954(2)Angstrom, b = 21.757(6)Angstrom, c = 21.130(7)Angstrom, V = 5035.0(2)Angstrom (3), D-cal = 1.062 Mg/m(3). In compound I and in both the molecules of compound II, the rings A, B & C are in chair conformation and the five membered ring D is in envelope conformation. The priority sequence attached to the chiral carbon C24 has "S" designation in compound I and "R" designation in compound II. The structures are stabilized by C-H . . .O and O-H---O hydrogen bonds.

Kinetics of catalytic degradation of polycarbonate in benzene

The degradation kinetics of polycarbonate [poly(bisphenol A carbonate)] in benzene catalyzed by commercial (rutile) TiO2 (BET surface area = 11 m(2)/g), anatase TiO2 (156 m(2)/g), and 1 atom % Pt/TiO2 (111 m2/g), prepared by the solution combustion technique, was investigated at various temperatures (230-280 degreesC) and 50 atm. The time evolution of the molecular weight distribution (MWD) was determined by gel permeation chromatography (GPC) and modeled with continuous distribution kinetics to obtain the degradation rate coefficients. The rate coefficients for the catalytic degradation of polycarbonate increased by factors of 20, 3.5, and 1.3 compared to the rate coefficients for thermal degradation when catalyzed by nanosized TiO2 anatase, Pt/TiO2 anatase, and commercial TiO2, respectively, at 280 degreesC. The increased catalytic activity of combustion for synthesized TiO2 and 1% Pt/TiO2 might be due to the increased acidity and BET surface area. The activation energies, determined from the temperature dependencies of the rate coefficients, were 16.3, 21.5, and 39.1 kcal/mol for commercial TiO2, combustion-synthesized Pt/TiO2, and anatase TiO2, respectively.

2-{[{2-Hydroxy-3-[2-methyl-5-(propan-2-yl)phenoxy]propyl}(pyridin -2-ylmethyl)amino]methyl}phenol

In the title racemic compound, C(26)H(32)N(2)O(3), an intramolecular O-H center dot center dot center dot N hydrogen bond is formed between the phenolic OH group and the tertiary amine N atom. Another O-H center dot center dot center dot N hydrogen bond that is formed between the OH group and the pyridine N atom links the molecules into a polymeric chain extending along the a axis. The structure is further stabilized by intramolecular and intermolecular C-H center dot center dot center dot O interactions.

Direct Infrared Absorption Spectroscopy of Benzene Dimer

The direct infrared (IR) absorption spectrum of benzene dimer formed in a free-jet expansion was recorded in the 3.3 mu m region for the first time. This has led to the observation of the C H stretching fundamental mode nu(13) (B(1u)), which is both IR and Raman forbidden in the monomer. Moreover, the IR forbidden and Raman allowed nu(7) (E(2g)) mode has been observed as well. These two modes were found to be red-shifted along with the IR allowed nu(20) (E(1u)) mode, as previously reported by Erlekam et al. [Erlekam; Frankowski; Meijer; Gert von Helden J. Chem. Phys. 2006, 124, 171101], using ion-dip spectroscopy, contrary to the blue-shift predicted earlier by theoretical studies. The observation of the nu(13) band indicates that the symmetry is reduced in the dimer, confirming the T-shaped structure observed by Erlekam et al. Our experimental results have not provided any direct evidence for the presence of the parallel displaced geometry, the main objective of the present work, as predicted by theoretical calculations.

Three-Component Chiral Derivatizing Protocols for NMR Spectroscopic Enantiodiscrimination of Hydroxy Acids and Primary Amines

The novel three-component chiral derivatization protocols have been derived for (1)H and (19)F NMR spectroscopic discrimination of a series of chiral hydroxy acids by their coordination and self-assembly with optically active a-methylbenzylamine and 2-formylphenylboronic acid. In addition, the optically pure (S)-mandelic acid in combination with 2-formylphenylboronic acid permits visualization of enantiomers of primary amines. These protocols have been demonstrated on enantiodiscrimination of chiral amines and hydroxy acids.