scispace - formally typeset
Search or ask a question

Showing papers on "Reaction rate constant published in 1971"


Journal ArticleDOI
TL;DR: It is concluded that the formation of a helical nucleus is the rate-determining step of recombination in the oligoadenylic—oligouridylic acid system and that three A · U base pairs form a stable nucleus.

404 citations


Journal ArticleDOI
TL;DR: Relaxation measurements on the kinetics of dimer formation by self complementary oligoribonucleotides of the form A(pA)n−1 (pU)n, 4 ≤ n ≤ 7.1 indicate longer helices grow more rapidly than they dissociate, with an activation energy roughly proportional to chain length.

389 citations


Journal ArticleDOI
TL;DR: Electrical relaxation experiments have been performed with phosphatidylinositol bilayer membranes in the presence of the ion carrier valinomycin, and the equilibrium constant of the heterogeneous association reaction M(+) (solution) + S (membrane) --> MS(+) (memBRane) is found to be approximately 1 M(-1), about 10(6) times smaller than the association constant in ethanolic solution.

215 citations


Journal ArticleDOI
TL;DR: In this paper, the authors show that the kinetics of mass transfer among aluminosilicates and aqueous solutions can be described by a simple parabolic rate law, which is consistent with diffusional mass transfer and applicable to incongruent as well as congruent reactions.

213 citations


Journal ArticleDOI
TL;DR: The study of the reaction between deoxyhemoglobin and a haptoglobin solution saturated with carbon monoxide indicates that hemoglobin tetramer is incapable of binding haPToglobin and its dissociation to dimers is a prerequisite for the reaction.

183 citations


Journal ArticleDOI
TL;DR: In this article, the rate constants for the deactivation of O2(1Δg) and relative rate constants of O 2(1 Δg+) have been deduced.

164 citations


Journal ArticleDOI
TL;DR: In this article, the effect of heat of reaction is considered based on the zone reaction model presented in Part I. The experimental thermal and transitional instabilities are compared with those from the grain model.

160 citations


Journal ArticleDOI
TL;DR: The activation energy for this reaction is 20 Kcal per mole as discussed by the authors, which is the activation energy of the Franck-Condon addition of an electron to ferricytochrome c in room temperature.

150 citations


Journal ArticleDOI
TL;DR: It is shown that weaker one-electron oxidizing agents made by reaction of OH with Br− or other solutes will oxidize NADH stoichiometrically to the NAD, and that the semiquinone made either by oxidation of NADH or reduction of NAD+ is produced.

148 citations


Journal ArticleDOI
TL;DR: In this article, the treatment of diffusion-controlled bimolecular chemical reactions is extended to molecules with axially symmetrical distributions of reactivity on their spherical surfaces, and the physically more interesting solution at large times can be obtained only approximately (though to any required degree of accuracy) by solving sets of linear equations.
Abstract: The treatment of diffusion‐controlled bimolecular chemical reactions is extended to molecules with axially symmetrical distributions of reactivity on their spherical surfaces. Whereas an explicit solution exists for the time‐dependent effective rate constant at small times, the physically more interesting solution at large times can be obtained only approximately (though to any required degree of accuracy) by solving sets of linear equations.

127 citations




Journal ArticleDOI
TL;DR: Comparison of the monolayer and bulk methods showed that both techniques are complementary, and the pH dependence and calcium requirements of the enzymatic reaction are similar under monolayers and bulk conditions.

Journal ArticleDOI
TL;DR: In this paper, the rate constants for adsorption and surface reaction were derived for a fixed-bed catalytic reactor with axial dispersion, particle-to-fluid diffusion, intraparticle diffusion, adaption, and a surface reaction.


Journal ArticleDOI
TL;DR: In this paper, the combustion rates of four size-graded fractions of semi-anthracite (78, 49, 22, and 6 μm) have been measured in the temperature range 1400-2200°K and at oxygen partial pressures of 0.1 and 0.2 atm.

Journal ArticleDOI
TL;DR: In this article, a fully converged, close-coupling calculation, using natural collision coordinates, is presented for the collinear H + H2 system, on a Porter-Karplus potential energy surface in the energy range of 9 to 35 kcal/mole.
Abstract: A fully converged, close-coupling calculation, using natural collision coordinates, is presented for the collinear H + H2 system, on a Porter-Karplus potential energy surface in the energy range of 9 to 35 kcal/mole. Eight closed channels were required for convergence in the threshold region. Inclusion of the closed channels alters considerably the numerical results. The effects of the vibrational non-adiabatic coupling terms were demonstrated. Particularly pronounced is the influence of the (energy dependent) inertial centrifugal energy due to the curvature of the reaction path. No evidence for tunnelling was obtained. The considerable difference between the quantal and classical reaction probabilities in the threshold energy region is entirely due to the non-adiabatic coupling terms, which tend to reduce the kinetic energy available along the reaction path, more so in the classical case, thereby leading to a higher dynamic threshold. The Arrhenius plot of the collinear rate constant shows more curvature...

Journal ArticleDOI
D.E. Nierode1, B.B. Williams1
TL;DR: A kinetic model for the reaction of hydrochloric acid with limestone has been determined in this paper, where acid reacted with a single calcium carbonate plate and the resulting model accurately represents the acid reaction process at the rock surface and is independent of mass-transfer rate.
Abstract: A kinetic model for the reaction of hydrochloric acid with limestone has been determined. Reaction order and rate constant for this model were calculated from experiments where acid reacted with a single calcium carbonate plate. Experiments were performed so that acid flow past the plate and mass transfer rate to the rock surface could be calculated theoretically. The resulting model, therefore, accurately represents the acid reaction process at the rock surface and is independent of mass-transfer rate. Combination of this model with existing theory allows prediction of acid reaction during acid-fracturing operations. A model for acid reaction in wormholes created during matrix acidization treatments is presented along with data for reaction of hydrochloric, formic, and acetic acids in a wormhole. Factors limiting stimulation in acid fracturing or matrix acidizing treatments are discussed. (27 refs.)

Journal ArticleDOI
TL;DR: The transient absorption spectra observed on pulse radiolysis of neutral aqueous solutions containing p-benzoquinone and excess methanol, ethanol, isopropanol and formate, saturated with nitrous oxide are reported in this paper.
Abstract: The transient absorption spectra observed on pulse radiolysis of neutral aqueous solutions containing p-benzoquinone and excess methanol, ethanol, isopropanol and formate, saturated with nitrous oxide are reported. The spectra are analogous to those obtained in solutions containing excess t-butanol and N2, O2, nicotinamide adenine dinucleotide or thymine and are attributed to the semiquinone radical-anion formed by electron transfer reactions with bimolecular rate constants k=ca. 109-1010 M–1 s–1. This assignment is supported by measurements of the acid dissociation constant of the absorbing product (pKa= 4.1) in solutions containing excess acetone and isopropanol.

Journal ArticleDOI
TL;DR: The change in rate constants of acylation on going from the aqueous phase into the micellar phase is dependent on the nature (aliphatic or aromatic) and the size of the side group R of the carboxylate and is interpreted as due to a different orientation of the reagent molecules in the micelle.

Journal ArticleDOI
TL;DR: In this article, the second-order rate constant for reaction with the hydrated electron did not change in the concentration range studied, and this was attributed to incomplete formation of the ionic atmosphere around the hydrate before reaction.
Abstract: Rate constants for reactions of the hydrated electron with a wide range of compounds, including simple salts and amino acids, have been measured in the time region 20–350 psec. In nearly all cases the second‐order rate constant for reaction with the hydrated electron did not change in the concentration range studied. However, the measured rate constant was in general different to that obtained in dilute solutions, and this was attributed to incomplete formation of the ionic atmosphere around the hydrated electron before reaction. Apart from the hydronium ion, Haq+, nearly all compounds decreased the initial hydrated electron yield: in all cases this decrease showed an exponential dependence on concentration. Compounds most efficient at decreasing the hydrated electron yield were cystine and cadmium salts, in both cases 0.39 mole/liter being needed to reduce the initial yield to 37%. The ability to reduce the initial yield showed no direct correlation with the corresponding hydrated electron rates. This an...

Journal ArticleDOI
TL;DR: In this article, an extrapolation technique was used to obtain relative rate constants for direct chemical population of the various vibrational levels for hydrogen fluoride formed in the gas-phase atom-molecule exchange reactions of atomic fluorine with hydrogen and methane.
Abstract: Infra-red emission has been detected from hydrogen fluoride formed in the gas-phase atom-molecule exchange reactions of atomic fluorine with hydrogen and methane. Emission was limited to that from vibrational levels v′ˇ-3 in each case. An extrapolation technique has been used to obtain relative rate constants for direct chemical population of the various vibrational levels. The values found were k 3tk2=0·76, k 2tk1=3·4 for the F + H2 reaction and k 3tk2=0·23, k 2 k 1=3·0 for the F + CH4 case.


Journal ArticleDOI
TL;DR: In this article, the high temperature, low pressure chlorination of single-crystal germanium and silicon was studied using modulated molecular beam techniques with mass spectrometric phase-sensitive detection.


Journal ArticleDOI
TL;DR: In this article, the collisional deactivation rate constants for O2(1Δg) by minor atmospheric constituents and other gases were determined by monitoring the intensity of its emission at 1.27 μ.
Abstract: This paper reports determinations of collisional deactivation rate constants for O2(1Δg) by minor atmospheric constituents and other gases. The benzene–oxygen photochemical system was used to produce O2(1Δg), and relative concentrations were measured by monitoring the intensity of its emission at 1.27 μ. The rate constants for the reaction O2(1Δg)+M→O2+M were 4.53 × 10−18, 5.60 × 10−18, and (0.5–1.0) × 10−19 (cm3 molecule−1·sec−1) for M=H2, H2O, and N2O, respectively. Upper limits were obtained for deactivation by He, Ar, CO2, and SF6 of 8.0 × 10−21, 8.3 × 10−21, 1.5 × 10−20, and 1.2 × 10−20, respectively. The temperature dependence of the deactivation of O2(1Δg) by oxygen has been investigated. The rate constant can be expressed in the form kO2 = 2.22 ± 0.09 × 10−18 (T / 300)n, where n = 0.78 ± 0.32 and T is the temperature in degrees Kelvin.

Journal ArticleDOI
TL;DR: Findings strongly support a mechanism in which the cyclodextrin reacts with HOCl to form a hypochlorite, and delivers this chlorine selectively to anisole bound in its cavity.

Journal ArticleDOI
TL;DR: In this paper, afterglow techniques have been employed to determine reaction rate constants for ions reacting in NO-H2O gas mixtures, and rate constants and/or equilibrium constants are provided for all forward and all reverse reactions at 296°K.
Abstract: Stationary afterglow techniques have been employed to determine reaction rate constants for ions reacting in NO–H2O gas mixtures. Krypton resonance radiation at 123.6 and 116.5 nm is used to ionize only the NO molecules. The NO+ ion is the precursor to a chain of reactions which result in NO+·nNO(n = 1,2), NO+·nH2O(n = 1,2,3), and H3O+·nH2O(n = 2,3,4) being formed. Rate constants and/or equilibrium constants are provided for all forward and all reverse reactions at 296°K.

Journal ArticleDOI
TL;DR: The main reaction of free-radical formation in oxidized polypropylene is of the type: ROOH + RH + RH → RH + R˙, which plays an important part in transport of free valence through solid polymer.
Abstract: Samples of polypropylene with adjacent and isolated hydroperoxide groups have been prepared. The rate constants of free-radical formation from solid hydroperoxides were measured by the inhibitor method. It was found that the free radicals yielded by adjacent hydroperoxide groups are formed more rapidly. The main reaction of free-radical formation in oxidized polypropylene is of the type: ROOH + ROOH → RO + H2O + RO2˙. The average yield of free radicals from polypropylene hydroperoxide is 2–4%. Oxygen has no effect on the yield of free radicals. However, the pressure of oxygen Po2 affects the rate of degenerate chain branching in polypropylene. The number of adjacent hydroperoxide groups and the rate of initiation increase with Po2. Consequently, a reaction of the type, R˙, + RH → RH + R˙, plays an important part in transport of free valence through solid polymer. This reaction is very fast in polyethylene, and no adjacent hydroperoxide groups are formed. The free radicals from polyethylene hydroperoxide are found to form by a reaction of the type: ROOH → RO˙ + HO˙.

Journal ArticleDOI
TL;DR: This work states that hydrolysis of esters in the presence of cr-chymotrypsin proceeds according to a mechanism involving at least three steps, and proposes a simple and reliable method of determining the constants.