A flash photolytic investigation of the photosolvolysis of α-(2,6-dimethoxyphenyl)vinyl chloride. Characterization of the 2,6-dimethoxyacetophenone keto–enol system

1993 ◽  
Vol 71 (11) ◽  
pp. 1964-1969 ◽  
Author(s):  
Yvonne Chiang ◽  
Robert Eliason ◽  
Joel Jones ◽  
A. Jerry Kresge ◽  
Kevin L. Evans ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Vinyl Chloride ◽  
Perchloric Acid ◽  
Pure Water ◽  
Acidity Constant ◽  
Transient Species ◽  
Vinyl Cation ◽  
Carbon Acid

Photosolvolysis of α-(2,6-dimethoxyphenyl)vinyl chloride in trifluoroethanol solution at 25 °C was found to produce the α-(2,6-dimethoxyphenyl)vinyl cation as a transient species with the lifetime τ = 1 μs. Addition of water reduced this lifetime markedly, until, at compositions greater than 80% water, it was too short to measure (τ < 20 ns); extrapolation of the data suggests τ = 9 ns in pure water. Hydration of this cation gave the much longer lived enol of 2,6-dimethoxyacetophenone, whose rates of ketonization were measured in dilute perchloric acid and sodium hydroxide solutions. These data, when combined with rates of enolization of the ketone determined by iodine scavenging, give pKE = 6.98 for the keto–enol equilibrium constant in the 2,6-dimethoxyacetophenone system, [Formula: see text] for the acidity constant of the enol ionizing as an oxygen acid, and [Formula: see text] for the acidity constant of the ketone ionizing as a carbon acid; these constants refer to wholly aqueous solution at 25 °C and ionic strength = 0.10 M.

Carboxylic acid amide enols: keto-enol/enolate interconversion of N-methylindoline-2-one and its 2-thione and 2-selone analogs in aqueous solution

1999 ◽  
Vol 77 (9) ◽  
pp. 1528-1536 ◽  
Author(s):  
A Jerry Kresge ◽  
Qingshui Meng
Keyword(s):  
Aqueous Solution ◽  
Isotope Effects ◽  
Acid Amide ◽  
Spectrophotometric Titration ◽  
Base Catalysis ◽  
Ionization Constants ◽  
Acidity Constant ◽  
Carbon Acid ◽  
Acid Ionization ◽  
Acid Ionization Constants

Carbon-acid ionization constants, QaK (concentration quotient at ionic strength = 0.10 M), were determined by spectrophotometric titration in aqueous solution for N-methylindoline-2-one, pQaK = 15.70, N-methylindoline-2-thione, pQaK = 8.93, and N-methylindoline-2-selone, pQaK = 7.25. Rate profiles were also constructed for the thione and selone. These were interpreted, with support from the form of acid-base catalysis as well as solvent and substrate isotope effects, as representing keto - enol/enolate ion interconversion. That led to the enol acidity constant pQaE = 4.05 and the keto-enol equilibrium constant pKE = 4.88 for the thione and estimates of the limits on these quantities, pQaE< 3 and pKE > 4, for the selone.Key words: lactam, thiolactam, selenolactam, keto-enol equilibria, carbon-acid ionization constants.

scholarly journals A study of factors influencing hydration of sodium hyaluronate from compressibility and high-precision densimetric measurements

1983 ◽  
Vol 213 (2) ◽  
pp. 363-369 ◽  
Author(s):  
A Davies ◽  
J Gormally ◽  
E Wyn-Jones ◽  
D J Wedlock ◽  
G O Phillips
Keyword(s):  
Aqueous Solution ◽  
Hyaluronic Acid ◽  
Ionic Strength ◽  
Pure Water ◽  
Bond Formation ◽  
Sodium Hyaluronate ◽  
Type Solution ◽  
Salt Form ◽  
Density Measurements ◽  
Factors Influencing

A study of the factors influencing the hydration of the biopolymer hyaluronic acid was made by compressibility and density measurements. The factors investigated were the hydration changes on glycosidic bond formation, and also the influence of counterion type, solution ionic strength and temperature. The results indicate that, with this biopolymer, the hydration of the glucuronate residue is significantly more than that of the N-acetylglucosamine residue, and further that the biopolymer is less hydrated than the sum of its component monosaccharide residues. Change of the counterion salt form of this polyelectrolyte from univalent to bivalent counterion type (Na+ to Ca2+) leads to a small though significant increase in the total hydration sheath surrounding the polymer. An increase in the background ionic strength of the solvent leads to a quantifiable lowering of the hydration of the polymer at physiological ionic strength compared with its value in salt-free aqueous solution. A decrease in hydration with increase in temperature in the range 20-50 degrees C is the opposite of previous reports, and was observed when the polymer was dissolved both in pure water and in 0.15 M-NaCl.

scholarly journals Study of the heterogeneous reaction of O<sub>3</sub> with CH<sub>3</sub>SCH<sub>3</sub> using the wetted-wall flowtube technique

2003 ◽  
Vol 3 (2) ◽  
pp. 1949-1971 ◽  
Author(s):  
M. Barcellos da Rosa ◽  
W. Behnke ◽  
C. Zetzsch
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Transport Model ◽  
Heterogeneous Reaction ◽  
Surface Film ◽  
Pure Water ◽  
Order Rate Constant ◽  
Uv Spectrophotometry ◽  
Henry's Law ◽  
Henry’S Law

Abstract. This work presents the heterogeneous kinetics of the reaction of CH3SCH3 (dimethyl sulphide, DMS) with O3 (ozone) in aqueous solution at different ionic strengths (0, 0.1 and 1.0 M NaCl) using the wetted-wall flowtube (WWFT) technique. Henry's law coefficients of DMS were determined on pure water and on different concentrations of NaCl (0.1 M–4.0 M) in the WWFT from UV spectrophotometric measurements of DMS in the gas phase using a numerical transport model of phase exchange to be H (M atm−1) = 2.16±0.5 at 274.4 K, 1.47±0.3 at 283.4 K, 0.72±0.2 at 291 K, 0.57±0.1 at 303.4 K and 0.33±0.1 at 313.4K on water, on 1.0M NaCl to be H = 1.57±0.4 at 275.7 K, 0.8±0.2 at 291 K and on 4.0 M NaCl to be H = 0.44±0.1 at 275.7 K and 0.16±0.04 at 29 K, showing a significant effect of ionic strength, mu, on the solubility of DMS according to the equation ln H = −4061 T−1 + 0.052 mu2 + 50.9 μ T−1 + 14.0. At concentrations ofDMS(liq) above 50 μ M, UV spectrophotometry of both O3(gas) and DMS(gas) enables us to observe simultaneously the reactive uptake of O3 on DMS solution and the gas-liquid equilibration of DMS along the flowtube. The uptake coefficient, gamma, of O3 on aqueous solutions of DMS, varying between 1 and 15×10−6, showed a square root-dependence on the aqueous DMS concentration (as expected for diffusive penetration into the surface film, where the reaction takes place in aqueous solution). It was smaller on NaCl solution in accord with the lower solubility of O3. The heterogeneous reaction of O3(gas) with DMS(liq) was evaluated from the observations of the second order rate constant (kII) for the homogeneous aqueous reaction O3(liq) + DMS(liq) using a numerical model of radial diffusion and reactive penetration and leading to kII (in units of 10−8M-1 s-1) = 4.1±1.2 at 291.0 K, 2.15±0.65 at 283.4 K and 1.8±0.5 at 274.4 K. Aside from the expected influence on solubility and aqueous-phase diffusion coefficient of both gases there was no significant effect of ionic strength on kII, that was determined for 0.1M NaCl, leading to kII (108M-1 s-1) = 3.2±1.0 at 288 K, 1.7±0.5 at 282 K and 1.3±0.4 at 276 K, and for 1.0 M NaCl, leading to 3.2±1.0 at 288 K, 1.3±0.4 at 282 K and 1.2±0.4 at 276 K, where the error limits include uncertainties of Henry's law constants and diffusion coefficients for DMS and O3.

Acid-catalyzed enolization of acetophenone: catalysis by bisulfate ion in sulfuric acid solutions

1986 ◽  
Vol 64 (6) ◽  
pp. 1224-1227 ◽  
Author(s):  
J. R. Keeffe ◽  
A. J. Kresge ◽  
J. Toullec
Keyword(s):  
Aqueous Solution ◽  
Sulfuric Acid ◽  
Acidity Constant ◽  
Acidity Function ◽  
Acid Solutions ◽  
Dilute Aqueous Solution ◽  
Acid Catalyzed ◽  
The Difference ◽  
Carbon Acid ◽  
Sulfuric Acid Solutions

Rates of acid-catalyzed enolization of acetophenone in dilute aqueous solution, measured under conditions where the solvated proton is the only acidic species present, give a hydrogen ion catalytic coefficient, [Formula: see text], that is 35% smaller than the value obtained by X acidity function extrapolation of measurements made in moderately concentrated sulfuric acid solutions. The difference may be attributed to catalysis by bisulfate ion in the sulfuric acid solutions; this is supported by direct measurement of the bisulfate ion catalytic coefficient in dilute sulfuric acid. This revised value of [Formula: see text] leads to new, but only slightly different, values of the keto–enol equilibrium constant for acetophenone in aqueous solution, pKE = 7.96 ± 0.04, the acidity constant for acetophenone ionizing as a carbon acid, [Formula: see text] and the encounter-controlled rate constant for the reaction of acetophenone enol with molecular bromine, k = (3.2 ± 0.4) × 109 M−1 s−1.

Extraction of hafnium(IV) with organophosphorus reagents from solutions of mineral acids mixtures

1979 ◽  
Vol 44 (12) ◽  
pp. 3656-3664
Author(s):  
Oldřich Navrátil ◽  
Jiří Smola ◽  
Rostislav Kolouch
Keyword(s):  
Ionic Strength ◽  
Aqueous Phase ◽  
Organic Phase ◽  
Perchloric Acid ◽  
Synergic Effect ◽  
Salting Out ◽  
Initial Concentration ◽  
Mixed Complexes ◽  
Synergic Extraction ◽  
Mineral Acids

Extraction of hafnium(IV) was studied from solutions of mixtures of perchloric and nitric acids and of perchloric and hydrochloric acids for constant ionic strength, I = 2, 4, 6, or 8, and for cHf 4 . 10-4 mol l-1. The organic phase was constituted by solutions of some acidic or neutral organophosphorus reagents or of 2-thenoyltrifluoroacetone, 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone, or N-benzoyl-N-phenylhydroxylamine in benzene, chloroform, or n-octane. A pronounced synergic extraction of hafnium proceeds only on applying organophosphorus reagents from an aqueous phase whose acidity is not lower than 3M-(HClO4 + HNO3) or 5M-(HClO4 + HCl). The synergic effect was not affected markedly by a variation of the initial concentration of hafnium in the range 1 . 10-8 -4 .10-4 mol l-1, it lowered with increasing initial concentration of the organophosphorus reagent and decreasing concentration of the H+ ions. It is suggested that the hafnium passes into the organic phase in the form of mixed complexes, the salting-out effect of perchloric acid playing an appreciable part.

Optical Absorption Spectroscopy of DNA-Wrapped HiPco Carbon Nanotubes

2019 ◽  
Vol 943 ◽  
pp. 95-99
Author(s):  
Li Jun Wang ◽  
Kazuo Umemura
Keyword(s):  
Carbon Nanotubes ◽  
Aqueous Solution ◽  
Optical Absorption ◽  
Absorption Spectroscopy ◽  
Near Infrared ◽  
Nir Spectroscopy ◽  
Optical Characterization ◽  
Optical Absorption Spectroscopy ◽  
Double Stranded Dna

Optical absorption spectroscopy provides evidence for individually dispersed carbon nanotubes. A common method to disperse SWCNTs into aqueous solution is to sonicate the mixture in the presence of a double-stranded DNA (dsDNA). In this paper, optical characterization of dsDNA-wrapped HiPco carbon nanotubes (dsDNA-SWCNT) was carried out using near infrared (NIR) spectroscopy and photoluminescence (PL) experiments. The findings suggest that SWCNT dispersion is very good in the environment of DNA existing. Additionally, its dispersion depends on dsDNA concentration.

Meso tetrakis ortho-, meta-, and para-N-alkylpyridiniopor-phyrins: kinetics of copper(II) and zinc(II) incorporation and zinc porphyrin demetalation

2003 ◽  
Vol 07 (03) ◽  
pp. 139-146 ◽  
Author(s):  
Peter Hambright ◽  
Ines Batinić-Haberle ◽  
Ivan Spasojević
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Effective Charge ◽  
Methyl Ethyl ◽  
Ionic Strength Dependence ◽  
Zinc Porphyrin ◽  
Cationic Porphyrin ◽  
Strength Dependence ◽  
Acid Catalyzed ◽  
Kinetics Of

The relative reactivities of the tetrakis( N -alkylpyridinium- X - yl )-porphyrins where X = 4 (alkyl = methyl, ethyl, n -propyl) , X = 3 (methyl) , and X = 2 (methyl, ethyl, n -propyl, n -butyl, n -hexyl, n -octyl) were studied in aqueous solution. From the ionic strength dependence of the metalation rate constants, the effective charge of a particular cationic porphyrin was usually larger when copper(II) rather than zinc(II) was the reactant. The kinetics of ZnOH + incorporation and the acid catalyzed removal of zinc from the porphyrins in 1.0 M HCl were also studied. In general, the more basic 4- (para-) and 3- (meta-) isomers were the most reactive, followed by the less basic 2- (ortho-) methyl to n -butyl derivatives, with the lipophilic ortho n -hexyl and n -octyl porphyrins the least reactive.

Determination of the complexation properties of a crosslinked poly(acrylic acid) gel with copper(II), nickel(II), and lead(II) in dilute aqueous solution

2001 ◽  
Vol 79 (4) ◽  
pp. 370-376 ◽  
Author(s):  
Catherine Morlay ◽  
Yolande Mouginot ◽  
Monique Cromer ◽  
Olivier Vittori
Keyword(s):  
Aqueous Solution ◽  
Ionic Strength ◽  
Acrylic Acid ◽  
Metal Ion ◽  
Conditional Stability ◽  
Binding Properties ◽  
Complex Species ◽  
Complexing Capacity ◽  
Dilute Aqueous Solution ◽  
Poly Acrylic Acid

The possible removal of copper(II), nickel(II), or lead(II) by an insoluble crosslinked poly(acrylic acid) was investigated in dilute aqueous solution. The binding properties of the polymer were examined at pH = 6.0 or 4.0 with an ionic strength of the medium µ = 0.1 or 1.0 M (NaNO3) using differential pulse polarography as an investigation means. The highest complexing capacity of the polyacid was obtained with lead(II) at pH = 6.0 with µ = 0.1 M, 4.8 mmol Pb(II)/g polymer. The conditional stability constants of the complex species formed were determined using the method proposed by Ruzic assuming that only the 1:1 complex species was formed; for lead(II) at pH = 6.0 and µ = 0.1 M, log K' = 5.3 ± 0.2. It appeared that the binding properties of the polymer increased, depending on the metal ion, in the following order: Ni(II) < Cu(II) < Pb(II). The complexing capacity and log K' values decreased with the pH or with an increase of the ionic strength. These results were in agreement with the conclusions of our previous studies of the hydrosoluble linear analogues. Finally, with the insoluble polymer, the log K' values were comparable to those previously obtained with the linear analogue whereas the complexing capacity values expressed in mmol g-1 were slightly lower.Key words: insoluble crosslinked poly(acrylic acid), copper(II), nickel(II), and lead(II) complexation.

scholarly journals STABILITY OF CODEINE: CHARACTERIZATION OF OXIDATION PRODUCTS OF CODEINE FORMED IN AQUEOUS SOLUTION

2013 ◽  
Vol 4 (7) ◽  
pp. 49-54
Author(s):  
Elahaj Babiker Mohamed ◽  
Shehab Naglaa Ahmed ◽  
Ali Heyam Saad
Keyword(s):  
Aqueous Solution ◽  
Oxidation Products
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