Room Temperature In Various Solvents Research Articles

Reaction Monitoring of Gold Oxides Prepared by an Oxygen-dc Glow Discharge from Gold Films in Various Aqueous Solutions by a Surface Plasmon Resonance-based Optical Waveguide Sensing System and X-ray Photoelectron Spectroscopy.

The chemical properties of thin (∼0.6 nm) gold oxide layers prepared by an oxygen-dc glow discharge from gold films at room temperature in various solvents and solutions were studied using a surface plasmon resonance (SPR)-based optical waveguide sensing system and X-ray photoelectron spectroscopy (XPS). New insights into the stability and reactivity of gold oxides under these conditions were obtained. The O 1s XPS spectra show three oxygen species, comprising components I, II, and III in the gold oxides, and components I and II are present in this order from the top surface of the oxide (component III). The gold oxide is stable in various solvents (water, methanol, ethanol, acetone, acetonitrile, diethyl ether, chloroform, hydrocarbons) for 10 - 30 min at room temperature. The gold oxide decomposes in aqueous 10-2 M solutions of acetaldehyde, hydrochloric acid, and sodium hydroxide during these periods. Gold oxide decomposition in these solutions was monitored by SPR and the decomposition rates were obtained. Decomposition of the gold oxides was confirmed and their surfaces were characterized after decomposition by XPS.

A Brief Synthesis of 2,2'-Arylmethylene Bis(3-hydroxy-5,5-dimethyl-2-cyclohexene-1- one) Catalyzed by TEAOH in Various Solvents.

2,2'-Arylmethylene bis(3-hydroxy-5,5-dimethyl-2-cyclohexene-1-one) having four carbonyl functionalities along with their tautomeric keto-enol forms, is an important biologically active compound and important synthetic intermediate in the synthesis of xanthenes. This study was conducted in order to develop a new and concise method of synthesis of 2,2'-arylmethylene bis (3-hydroxy-5,5-dimethyl-2- cyclohexene-1-one) derivatives. TEAOH (20 mol %) was fond to be as a simple and efficient catalyst for the preparation of 2,2'-arylmethylene bis(3-hydroxy-5,5-dimethyl-2-cyclohexene-1-one) derivatives by the Knoevenagel condensation/Michael addition tandem reactions. A concise and practical method was developed for one-pot synthesis of 2,2'-arylmethylene bis(3- hydroxy-5,5-dimethyl-2-cyclohexene-1-one) derivatives catalyzed by TEAOH at room temperature in various solvents. This strategy provides several advantages over the traditional synthetic method, and is applicable to a wide variety of aromatic and heteroaromatic aldehydes at room temperature in various solvents.

Photophysical Properties of a Novel and Biologically Active 3(2H)-Pyridazinone Derivative Using Solvatochromic Approach.

Herein, we report photophysical properties of a novel and biologically active 3(2H)-pyridazinone derivative 5-(4-chloro-2-hydoxy-phenyl)-2-phenyl-2H-pyridazin-3-one [CHP] molecule using solvatochromic approaches. Absorption and fluorescence spectra of CHP molecule have been measured at room temperature in various solvents of different polarities. From this, it is observed that the positions, intensities and shapes of the absorption and emission bands are usually modified. Experimentally, the ground and excited state dipole moments are estimated using solvatochromic shift method which involves Lippert's, Bakshiev's and Kawski-Chamma-Viallet's equations. Theoretically, the ground state dipole moment was estimated using the Gaussian-09 program. The value of ground state dipole moment estimated using experimental and theoretical methods are well correlated. This inference that the molecular geometry is taken for CHP molecule under theoretical and experimental methods are similar. Further, we observed that the excited state dipole moment (μ e ) is greater than the ground state dipole moment (μ g ) which indicates that the excited state is more polar than the ground state. Furthermore, we have estimated an angle between the ground and excited state dipole moments. In addition, we have estimated the fluorescence quantum yield of CHP molecule using Rhodamine B as a standard reference in different solvents.

English

African black soap is an indigenous African organic soap formed by esterification. This was prepared by reacting palm kernel oil and the filtrate of cocoa pod ash. Chemical analyses revealed the moisture content was 26% (w/w), total fatty matter (TFM) was 44.75% (w/w), total fatty alkaline (TFA) was 0.22% (w/w), total alkaline (TA) was 11.78% (w/w) and pH was 10. The metal complexes were formed by the reaction of the synthesized black soap with some transition metal salts which included Cu(CH3COO)2.H2O, Pb(CH3COO)2.3H2O and FeCl3. The metal:ligand ratio, that is, M:L = 3:1, while the reaction was carried out in an aqueous medium to afford [Pb(C11H23COO-K+)2(C11H23COO-)2].9H2O, [Cu(BL)4(C11H23COO-)2].4H2O and [Fe(BL)2(C11H23COO-)Cl2] with the percentage yield of 56, 48 and 41%, respectively. Characterization of the black soap and complexes was done by spectroscopic analyses and determination of physicochemical properties. The solubility of the metal complexes was determined at room temperature in various solvents. Results showed that solubility increased as polarity decreased and it was most effective with non-polar organic solvents. Potassium ester (C11H23COO-K+), commonly called African black soap, has acted either as a monodentate or bidentate ligand forming metal complexes by coordinating through one or two of its oxygen donor atoms and also by entirely replacing the potassium ion with the transition metal (displacement reaction). Spectra analyses corroborate an octahedral structure for the Pb(II), a distorted octahedral structure for the Cu(II) and an octahedral Fe(III) complex. Key words: African black soap, esterification, metal complexes.

Spectroscopic studies on newly synthesized 5-(2-hydroxy-5-methoxy-phenyl)-2-phenyl-2H-pyridazin-3-one molecule

Spectroscopic studies on newly synthesized biologically active pyridazin-3(2H)-one derivative 5-(2-hydroxy-5-methoxy-phenyl)-2-phenyl-2H-pyridazin-3-one (HMPP) molecule have been studied at room temperature in various solvents of different polarities. Theoretically, the ground state dipole moment was calculated using the Gaussian-09 program and experimentally by Guggenheim and Higasi methods. Calculated ground state dipole moment value by these three methods is well correlated. It is an inference that the molecular geometry is taken for HMPP molecule under theoretical and two experimental methods are similar. The excited state dipole moment (μe) was calculated using solvatochromic shift method which involves two equations proposed by Bakshiev's and Kawski-Chamma-Viallet's. The change in dipole moment (∆μ) was calculated both from solvatochromic shift method and microscopic solvent polarity parameter (ETN)later on the value is compared. We found that the excited state dipole moment (μe) is greater than the ground state dipole moment (μg) which indicates that the excited state is more polar than the ground state. Further, we studied the solvent effect on the spectral characteristics using the methods as suggested by Kamlet and Catalan. Furthermore, we studied the fluorescence quenching of HMPP molecule using aniline as a quencher in different solvents at room temperature, with a view to understanding the role of the activation process in a quenching mechanism. The probability of quenching per encounter (p) is determined in all solvents. Lastly, activation energy (Ea) of quenching was calculated using the literature value of activation energy for diffusion (Ed) and experimentally calculated value of p. The magnitude of these parameters indicates that the quenching phenomenon in HMPP molecule is due to an activation process.

The Solvent Effects on the Formation of Polyynes by Laser Ablation

(≥ 99.0%), n-octane (≥ 99.0%). These solvents were purchased from Sigma-Aldrich and used without further purification. The surface of the graphite target was polished with 1200grade emery paper prior to laser irradiation using a Qswitched Nd:YAG laser (Continuum, Surelite I, λ = 1064 nm, pulse duration 5 ns) operated at 10 Hz. The energy of the laser was maintained at 20 mJ/pulse in order to avoid generation of splashes. The laser beam was loosely focused using a lens with a focal length of 300 mm and the typical irradiation time was 20 min. The solution was stirred during the ablation using a magnetic stirrer. The target was also continuously rotated to minimize the effect of target aging and to provide some stirring effect. The optical properties of the nascent polyynes solutions were studied at room temperature in various solvents by a UV-vis absorption spectrophotometer (Shimadzu UV1800) and normal Raman spectra were recorded by a spectrophotometer (HORIBA T64000).

Effect of anisotropic and isotropic solvent on the dipole moment of coumarin dyes

The ground state ( μ g) and the excited state ( μ e) dipole moments of two coumarin laser dyes, coumarin 440 and 460, were studied at room temperature in various solvents, viz., general solvents, alcohols and liquid crystals at 298 K. In this work, we report dipole moment of laser dyes in different anisotropic (liquid crystal) and isotropic environments for understanding the effects of environments on the molecular dipole moment and comparing them. Ground and excited state dipole moments of coumarin dyes were evaluated by means of solvatochromic shift method. It was observed that dipole moment values of excited states ( μ e) were higher than the corresponding ground state values ( μ g) in all media.

Anisotropic media effect on the dipole moment of some coumarin dyes

The ground state ( μ g) and the excited state ( μ e) dipole moments of two coumarin laser dyes, C500 and C503, were studied at room temperature in various solvents, viz., aprotic solvents, alcohols and liquid crystals at 298 K. We report dipole moment of laser dyes in different anisotropic (liquid crystals) and isotropic environments. The dipole moments values in different media help to investigate environment effects on the molecular dipole moment and provide a straightforward method for comparing their properties. Ground and excited state dipole moments of coumarin dyes were evaluated by means of solvatochromic shift method. It was observed that dipole moment values of excited states ( μ e) were higher than corresponding ground state values ( μ g), indicating a substantial redistribution of the π-electron densities in a more polar excited state for the dyes investigated.

Chemoselective Staudinger‐Phosphite Reaction of Azides for the Phosphorylation of Proteins

Extending the toolbox: The title reaction was identified as a chemoselective means to modify azides in peptides and proteins in high yields at room temperature in various solvents including aqueous buffers at physiological pH. In combination with nonnatural protein translation the Staudinger-phosphite reaction allows the site-specific incorporation of phosphorylated Tyr analogues in proteins.

Estimation of ground and excited state dipole moments of some laser dyes

The ground state ( μ g) and the excited state ( μ e) dipole moments of three laser dyes namely 2, 5-diphenyl-1, 3, 4- oxadiazole (PPD), 2, 2″-dimethyl-p-terphenyl (DMT) and 1, 3-diphenyl benzene (MT) were studied at room temperature in various solvents. The ground state dipole moments ( μ g) of all the three laser dyes were determined experimentally by Guggenheim method. The excited state dipole moments ( μ e) were estimated from Lippert’s, Bakshiev’s and Chamma Viallet’s equations by using the variation of the Stokes shift with the solvent dielectric constant and refractive index. Ground and excited state dipole moments were evaluated by means of solvatochromic shift method and also the excited state dipole moments are determined in combination with ground state dipole moments. It was observed that dipole moment values of excited states ( μ e) were higher than corresponding ground state values ( μ g), indicating a substantial redistribution of the π-electron densities in a more polar excited state for all the dyes investigated.

Steady-state, time-resolved fluorescence polarization behaviour and determination of dipole moments of coumarin laser dye

Steady-state and time-resolved fluorescence polarization studies have been carried out on coumarin 30 laser dye. The rotational reorientation of this probe has been measured in butanol at higher values of viscosity varying temperature. It is found that coumarin 30 rotates faster in butanol than in n-octanenitrile. The ground state ( μ g) and the excited state ( μ e) dipole moments are studied at room temperature in various solvents. These have been measured using absorption and fluorescence spectral band shift in solvent with varying dielectric constant ( ε) and refractive index ( n). It is observed that the dipole moment of excited state is higher than ground state dipole moment.

Ground and excited state dipole moments of exalite 404 and exalite 417 UV laser dyes determined from solvatochromic shifts of absorption and fluorescence spectra

The ground state ( μ g) and the excited state ( μ e) dipole moments of two exalite dyes were studied at room temperature in various solvents. The dipole moments ( μ g and μ e) were estimated from solvatochromic shifts of absorption and fluorescence spectra as function of the dielectric constant ( ε) and refractive index ( n). The results show that excited state dipole moments of exalite 404 and exalite 417 dyes (radii a=4.968 and 5.902 Å) are 2.419 and 3.977 D, respectively; and the change in the dipole moments were found to be 1.243 and 2.106 D. It was observed that the dipole moments of excited state were higher than those of ground state for both the dyes.

Enantioselective conjugate addition of diethylzinc using catalytic silver(I) diaminocarbenes and Cu(OTf) 2

Chiral silver(I) diaminocarbenes act as efficient carbene transfer agents to copper salts. The catalytic species, active in the conjugate addition of diethylzinc to cyclohexenone, is prepared easily at room temperature in various solvents by simply mixing the silver carbene and Cu(OTf) 2. This method avoids the use of strong bases and polar solvents to generate the carbene. The chiral diaminocarbene–copper catalyst, formed in situ, shows a strong accelerating effect and gives enantiomeric excesses up to 23%.

Amino acid catalyzed direct asymmetric aldol reactions: a bioorganic approach to catalytic asymmetric carbon-carbon bond-forming reactions.

Direct asymmetric catalytic aldol reactions have been successfully performed using aldehydes and unmodified ketones together with commercially available chiral cyclic secondary amines as catalysts. Structure-based catalyst screening identified L-proline and 5,5-dimethyl thiazolidinium-4-carboxylate (DMTC) as the most powerful amino acid catalysts for the reaction of both acyclic and cyclic ketones as aldol donors with aromatic and aliphatic aldehydes to afford the corresponding aldol products with high regio-, diastereo-, and enantioselectivities. Reactions employing hydroxyacetone as an aldol donor provide anti-1,2-diols as the major product with ee values up to >99%. The reactions are assumed to proceed via a metal-free Zimmerman-Traxler-type transition state and involve an enamine intermediate. The observed stereochemistry of the products is in accordance with the proposed transition state. Further supporting evidence is provided by the lack of nonlinear effects. The reactions tolerate a small amount of water (<4 vol %), do not require inert reaction conditions and preformed enolate equivalents, and can be conveniently performed at room temperature in various solvents. In addition, reaction conditions that facilitate catalyst recovery as well as immobilization are described. Finally, mechanistically related addition reactions such as ketone additions to imines (Mannich-type reactions) and to nitro-olefins and alpha,beta-unsaturated diesters (Michael-type reactions) have also been developed.

Anisotropy time dependence of photoexcited C60 and C70 in transient grating experiments. Solvent effect

Anisotropy time dependence of photoexcited C50 and C70 has been measured by picosecond transient grating techniques at room temperature in various solvents. The monoexponential anisotropy decay was observed for the C60 molecule and biexponential anisotropy decay was observed for the C70 molecule. Both for the C60 and for the C70 molecules anisotropy time decay is very fast. The data obtained were analyzed in terms of the rotational reorientation of fullerene molecules in solvents. Hynes-Kapral-Weinberg theory reasonably explains the observed reorientation times of fullerenes molecules. The dielectric friction effect on the C70 rotational reorientation on the short axis is reported.

Solvent effect in the addition of thetert-butyl radical to acrylonitrile

CW and kinetic ESR spectroscopy are applied to determine rate constants for the addition of thetert-butyl radical to acrylonitrile at room temperature in various solvents. They increase with increasing solvent polarity from 2.8·106 M−1s−1 for tetradecane to 10.2·106 M−1s−1 for acetonitrile. This solvation effect indicates a substantial charge-transfer in the transition state for the addition and supports previous notations of the nucleophilicity oftert-butyl. A comparison oftert-butyl with hex-5-enyl and methyl is also given.

Reactivity of cationic molybdenum(II) complexes. Part 3. Synthesis of methoxide and carbomethoxide derivatives of η-pentamethylcyclopentadienyl–molybdenum(II) and the crystal structure determination of the oxidation product trans-[{Mo(η-C5Me5)(O)2}2(µ-O)

The complex [Mo(CO)3(η-C5Me5){P(OMe)3}]BF4(1) reacts in methanol solution with Na(OMe) to give a mixture of cis- and trans-[Mo(CO)2(η-C5Me5){P(OMe)3}(CO2Me)](3). Compound (3) decarbonylates at room temperature in various solvents giving a mixture of cis- and trans-[Mo(CO)2(η-C5Me5){P(OMe)3}(OMe)](4). The complex [Mo(CO)3(η-C5Me5)] BF4(2) reacts in methanol solution with Na(OMe) affording the insoluble complex [{Mo(CO)2(η-C5Me5)(OMe)}n](5) which is monomerized by reaction with P(OMe)3 in refluxing tetrahydrofuran (thf); trans-(4) is the main product of this reaction. Oxidation of a thf suspension of [{Mo(CO)2(η-C5Me5)(OMe)}n] by oxygen gives the MoVI derivative [{Mo(η-C5Me5)(O)2}2(µ-O)](6), together with unidentified products. The X-ray crystal structure of (6) has been established: (6) is monoclinic, space group P21/a, a= 17.677(6), b= 9.248(1), c= 21.272(6)A, β= 101.68(2)°, Z= 6.

Crystal structure and optical and magnetic properties of tetrakis(diethylamido)uranium(IV), a five-coordinate dimeric complex in the solid state

The volatile U(IV) compound U(N(C/sub 2/H/sub 5/)/sub 2/)/sub 4/ is dimeric in the solid state and exhibits an unusual and possibly unique five coordination about the U ion for an f series ion. The crystals are monoclinic, space group P2/sub 1//n. At 23/sup 0/C a = 9.326 (4) A, b = 17.283 (8) A, c = 13.867 (6) A, ..beta.. = 108.43 (5)/sup 0/, and d/sub c/ = 1.65 g/cm/sup 3/ for Z = 4. X-ray diffraction intensity data were collected by an automated diffractometer using graphite monochromated Mo K..cap alpha.. radiation. For 1809 reflections with F/sup 2/ less than 2 sigma(F/sup 2/), R/sub 1/ = 0.035 and R/sub 2/ = 0.031. The five-coordinate uranium atom is at the center of a distorted trigonal bipyramid of nitrogen atoms; two of these bipyramids share an edge to make a dimeric complex located on a center of symmetry. The nearest approach of the uranium atoms is 4.004 (1) A. The three nonbridging U--N distances average 2.22 (2) A whereas the bridging U--N distances are 2.46 and 2.57 A. The N--U--N and U--N--U angles in the central cluster are 74.4 (3) and 105.6 (3)/sup 0/, respectively. The optical and proton magnetic resonance spectramore » of U(NEt/sub 2/)/sub 4/ at room temperature in various solvents are reported. Temperature-dependent magnetic susceptibility measurements on the solid show Curie--Weiss behavior from 10 to 100/sup 0/K. Below 10/sup 0/K the susceptibility becomes temperature independent and there is no indication of magnetic ordering. A greater tendency in U amide chemistry toward oligomerization than in the d transition series is suggested.« less

Rotational isomerism: V. A nuclear magnetic resonance study of 1,2-diiodoethane

The nuclear magnetic resonance spectrum of 1,2-diiodoethane has been recorded at room temperature in various solvents and at −28° in CS 2. The protonproton coupling parameters have been obtained from an analysis of the 13 C-satellite spectra. The energy difference between the rotational isomers of 1,2-diiodoethane has been calculated as a function of the solution dielectric constant with a classical reaction field theory. An energy difference in the vapour phase of 2.45 kcal mole −1 has been derived. The vicinal coupling constants for the individual isomers have been obtained from the solvent dependence. They are: trans isomer, J t = 14.20 Hz, J g = 4.89 Hz; gauche isomer, J t+ J g' = 15.55 Hz, J g' = 3.20 Hz. Values for the gauche and trans coupling constants in ethane ( J t = 15.0 Hz, J g = 4.5 Hz) and empirical parameters for the Karplus equation have been derived.