Catalysis by α-cyclodextrin of the reaction of formic acid with bromine

1990 ◽  
Vol 68 (11) ◽  
pp. 2119-2121 ◽  
Author(s):  
Oswald S. Tee ◽  
Bushra Javed ◽  
Susan R. Mikkelsen
Keyword(s):  
Formic Acid ◽  
Dissociation Constant ◽  
Rate Constants ◽  
Reaction Conditions ◽  
Value Analysis ◽  
Potentiometric Measurements

α-Cyclodextrin (CD) modestly increases the rate of oxidation of formic acid by bromine. The variation of rate constants with [Br−] is consistent with dominance of the formation of a CD•Br3− complex in determining the fraction of free Br2 and the CD•Br2 complex, under the reaction conditions. Potentiometric measurements support a dissociation constant of about 0.2 mM for the CD•Br3− complex, in agreement with an earlier spectrophotometric value. Analysis of the rate increases with [CD] implies that CD•Br2 is more reactive (~10 times) than free Br2 towards formate ion, as was found for phenols. These conclusions differ from those of another recent study. Keywords: catalysis, α-cyclodextrin, oxidation, formic acid, bromine.

scholarly journals Prebiotic Route to Thymine from Formamide—A Combined Experimental–Theoretical Study

Molecules ◽  
2021 ◽  
Vol 26 (8) ◽  
pp. 2248
Author(s):  
Lukáš Petera ◽  
Klaudia Mrazikova ◽  
Lukas Nejdl ◽  
Kristyna Zemankova ◽  
Marketa Vaculovicova ◽  
...  
Keyword(s):  
Formic Acid ◽  
Quantum Chemical ◽  
Prebiotic Chemistry ◽  
Theoretical Study ◽  
Reaction Pathway ◽  
Hydrolysis Product ◽  
Current Paper ◽  
Reaction Conditions ◽  
Chemical Modeling ◽  
Chemistry Research

Synthesis of RNA nucleobases from formamide is one of the recurring topics of prebiotic chemistry research. Earlier reports suggest that thymine, the substitute for uracil in DNA, may also be synthesized from formamide in the presence of catalysts enabling conversion of formamide to formaldehyde. In the current paper, we show that to a lesser extent conversion of uracil to thymine may occur even in the absence of catalysts. This is enabled by the presence of formic acid in the reaction mixture that forms as the hydrolysis product of formamide. Under the reaction conditions of our study, the disproportionation of formic acid may produce formaldehyde that hydroxymethylates uracil in the first step of the conversion process. The experiments are supplemented by quantum chemical modeling of the reaction pathway, supporting the plausibility of the mechanism suggested by Saladino and coworkers.

An efficient and eco-friendly method for the thiol-Michael addition in aqueous solutions using amino acid ionic liquids (AAILs) as organocatalysts

2020 ◽  
Vol 92 (1) ◽  
pp. 97-106
Author(s):  
Roberto Figueroa Guíñez ◽  
José G. Santos ◽  
Ricardo A. Tapia ◽  
Jackson J. Alcazar ◽  
Margarita E. Aliaga ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Ionic Liquids ◽  
Amino Acid ◽  
Efficient Method ◽  
Michael Addition ◽  
Rate Constants ◽  
Michael Reaction ◽  
High Rate ◽  
Reusable Catalyst ◽  
Reaction Conditions

AbstractA series of amino-acid based ionic liquids (Bmim[AA]s) have been synthesized and evaluated as catalysts, in aqueous solution. The results of a kinetic study of the thiol-Michael reaction of L-Cysteine with trans-β-nitrostyrene demonstrated the advantages of using (Bmim[AA]s) as organocatalysts. The benefits include high rate constants; mild reaction conditions; and, a reusable catalyst, which leads to a simple and efficient method for these important kinds of reactions.

scholarly journals The accessibility of protein-bound dinitrophenyl groups to univalent fragments of anti-dinitrophenyl antibody

1976 ◽  
Vol 159 (2) ◽  
pp. 323-333 ◽  
Author(s):  
C G Knight ◽  
N M Green
Keyword(s):  
Dissociation Constant ◽  
Rate Constants ◽  
Alkyl Chain ◽  
Dissociation Constants ◽  
Tryptophan Fluorescence ◽  
Thiol Group ◽  
Second Order ◽  
Thiol Compounds ◽  
Order Rate ◽  
Chain Lengths

A series of N-(N-dinitrophenylaminoalkyl)maleimides were sythesized with alkyl-chain lengths of two, four and six carbon atoms. When these compounds reacted with the thiol group of mercaptalbumin, the tryptophan fluorescence of the protein was quenched. This change in fluorescence was used to determine the rate of reaction of the Dnp (dinitrophenyl)-maleimides with mercaptalbumin. The second-order rate constants were similar to those observed in reactions between low-molecular-weight thiol compounds and maleimides. When N-(N-Dnp-aminoalkyl)succinimidomercaptalbumins were added to univalent fragments of anti-Dnp antibody the antibody fluorescence was quenched. Florescence-quenching titrations showed that the protein-bound Dnp groups were fully available to the antibody even when the alkyl chain was short. The apparent dissociation constants were significantly > that of the interaction between anti-Dnp antibody and the free hapten, 6-(N-Dnp)-aminohexanoate. The antibody fluorescence was quenched efficienty by [dnp-Lys41]ribonuclease A, also with an increased dissociation constant. It could be concluded from the increase in dissociation constant that the Dnp group spent no more than 0.1% of its time in the dissociated state, available to antibody. The second-order rate constants for the association between the Dnp-mercaptablumins and the antibody were determined and were similar in magnitude to those observed in other interactions between protein and anti-protein antibody.

Kinetics and Modelling of Bulk and Solution Diallyl Terephthalate Polymerization

2006 ◽  
Vol 4 (1) ◽  
Author(s):  
Iztok Hace
Keyword(s):  
Kinetic Model ◽  
Kinetic Parameters ◽  
Rate Constants ◽  
Chain Transfer ◽  
Average Molecular Weight ◽  
Propagation Rate ◽  
Reaction Conditions ◽  
Diffusion Limitations ◽  
Kinetics Of ◽  
Dicyclohexyl Peroxydicarbonate

Free radical polymerization kinetics of diallyl terephthalate (DAT) in solution was investigated with two different peroxide initiators: dicyclohexyl peroxydicarbonate (CHPC) and benzoyl peroxide (BPO) in temperature range from 50°C to 110°C, where ortho-xylene was used as a solvent. Conversion points were measured using Fourier Transform Infrared (FTIR) measurements. Previously developed kinetic model for bulk DAT polymerization, was extended to solution DAT polymerization. The ratio of solvent chain - transfer rate constants to propagation rate constants of the polymerization system were found between 1.25 10-4 to 1.68 10-4 for various reaction conditions. They were obtained using the calculated initial polymerization rates and the number average molecular weight measurements made by GPC. The effect of different solvent fractions and initiator concentrations on the diffusion limitations were investigated. Only two kinetic parameters, kpd0 and ktd0 were obtained by fitting the kinetic model onto measured conversions for various reaction conditions at 0.2, 0.5 and 0.8 solvent fractions. Thus obtained kpd0 and ktd0 kinetic parameters were extrapolated to zero solvent fractions and from obtained values of kinetic parameters the conversion points for bulk DAT polymerization were calculated and compared to measured conversion points.

scholarly journals Kinetic Evidence for Near Irreversible Nonionic Micellar Entrapment ofN-(2′-Methoxyphenyl)phthalimide (1) under the Typical Alkaline Reaction Conditions

2014 ◽  
Vol 2014 ◽  
pp. 1-6
Author(s):  
M. Niyaz Khan ◽  
Yoke-Leng Sim ◽  
Azhar Ariffin
Keyword(s):  
Kinetic Analysis ◽  
Alkaline Hydrolysis ◽  
Rate Constants ◽  
Total Concentration ◽  
Reaction Conditions ◽  
First Order ◽  
Order Rate ◽  
Alkaline Reaction ◽  
Pseudo First Order ◽  
Hydrolysis Of

The values of pseudo-first-order rate constants (kobs) for alkaline hydrolysis of1, obtained at 1.0 mM NaOH and withinCmEnT(total concentration ofCmEn) range of 3.0–5.0 mM forC12E23and 10–20 mM forC18E20, fail to obey pseudophase micellar (PM) model. The values of the fraction of near irreversibleCmEnmicellar trapped1molecules (FIT1) vary in the range ~0–0.75 forC12E23and ~0–0.83 forC18E20under such conditions. The values ofFIT1become 1.0 at ≥10 mMC12E23and 50 mMC18E20. Kinetic analysis of the observed data at ≥10 mMC12E23shows near irreversible micellar entrapment of1molecules under such conditions.

The thermal decomposition of diethyl ether. II. Analytical survey of the reaction products as a function of reaction conditions

1958 ◽  
Vol 245 (1240) ◽  
pp. 40-48 ◽  
Keyword(s):  
Thermal Decomposition ◽  
Rate Constants ◽  
Vapour Phase ◽  
Mass Spectrometric ◽  
Spectrometric Analysis ◽  
Reaction Products ◽  
Reaction Conditions ◽  
True Rate ◽  
Carbon Tetrafluoride ◽  
Pressure Changes

By mass-spectrometric analysis combined with vapour-phase chromatography the reaction products from the thermal decomposition of ether have been determined at various stages of the reaction (uninhibited and inhibited by nitric oxide) for initial ether pressures of 80 to 1000 mm. The effects of added hydrogen and of carbon tetrafluoride on the composition of the products have also been examined. No major changes in the chemistry of the reaction occur with these variations in conditions. Factors are given for calculating true rate constants from pressure changes accompanying the reaction. Corrected values of rate constants vary with the conditions in the same way as the values derived from uncorrected pressure changes, the correspondence being close for the uninhibited reaction.

STUDIES IN THE WAGNER–MEERWEIN REARRANGEMENT: PART V. RATES OF FORMOLYSIS OF SOME 9-ALKYL-9-FLUORENYLMETHYL TOSYLATES

1965 ◽  
Vol 43 (9) ◽  
pp. 2465-2467 ◽  
Author(s):  
F. A. L. Anet ◽  
P. M. G. Bavin
Keyword(s):  
Formic Acid ◽  
Rate Constants ◽  
Alkyl Group

For a series of 9-alkyl-9-fluorenylmethyl p-toluenesulfonates, the rates of decomposition in formic acid increase with the size of the alkyl group. Changes in the rate constants are associated with changes in ΔS≠.

scholarly journals Equilibrium and Kinetic Properties of the Interaction between Tetrodotoxin and the Excitable Membrane of the Squid Giant Axon

1970 ◽  
Vol 55 (3) ◽  
pp. 309-335 ◽  
Author(s):  
Leon Andres Cuervo ◽  
William J. Adelman
Keyword(s):  
Dissociation Constant ◽  
Rate Constants ◽  
Sodium Current ◽  
Giant Axon ◽  
Kinetic Properties ◽  
Bathing Solution ◽  
Thermodynamic Quantities ◽  
Partial Recovery ◽  
Reactive Site ◽  
Membrane Complex

Squid giant axons were treated with tetrodotoxin (TTX) in concentrations ranging from 1 nM to 25 nM and the resulting decrease in sodium current was followed in time using the voltage clamp technique. The removal of TTX from the bathing solution produced only partial recovery of the sodium current. This suggests that the over-all interaction is more complex than just a reversible reaction. By correcting for the partial irreversibility of the decrease in sodium current, a dissociation constant of 3.31 x 10-9 M was calculated for the reaction between TTX and the reactive site of the membrane. The data obtained fit a dose-response curve modified to incorporate the correction for partial irreversibility when calculated for a one-to-one stoichiometry. The fit disagreed with that calculated for a reaction between two molecules of TTX with a single membrane-reactive site, but neither supported nor disproved the possibility of a complex formed by two reactive sites with one molecule of TTX. Values of the rate constants for the formation and dissociation of the TTX-membrane complex, k1 and k2, respectively, were obtained from the kinetic data. The values are: k1 = 0.202 x 108 M-1, and k2 = 0.116 min-1. The magnitude of the dissociation constant derived from these values is 5.74 x 10-9 M, which has the same order of magnitude as that obtained from equilibrium measurements. Arrhenius plots of the rate constants gave values for the thermodynamic quantities of activation.

General Catalytic Methylation of Amines with Formic Acid under Mild Reaction Conditions

2014 ◽  
Vol 20 (26) ◽  
pp. 7878-7883 ◽  
Author(s):  
Iván Sorribes ◽  
Kathrin Junge ◽  
Matthias Beller
Keyword(s):  
Formic Acid ◽  
Reaction Conditions
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