Kinetics and Mechanism of the Copper-Catalyzed Etching of Silicon by F2

1987 ◽  
Vol 111 ◽  
Author(s):  
N. Selamoglu ◽  
J. A. Mucha ◽  
D. L. Flamm ◽  
D. E. Ibbotson
Keyword(s):  
Etch Rate ◽  
Reaction Rate ◽  
Active Species ◽  
Zero Order ◽  
Feature Size ◽  
First Order ◽  
Size Dependent ◽  
Copper Compounds ◽  
Catalytically Active ◽  
Active Intermediates

AbstractThe copper catalyzed fluorination of silicon is first-order in [F2] and in [Cu]s until the coverage reaches ∼4 monolayers. Above ∼4 monolayers the reaction rate is zero order in copper, suggesting a limited number of catalytically active Cu/Si sites. Surface diffusion of copper leads to decrease in the etch rate as a function of time as well as feature size-dependent etch depths. The copper compounds CuF2, CuO, and copper silicides, Cu5 Si and Cu3 Si all catalyzed the F2-Si reaction which suggests that they are all converted to the same active species. The results can be explained by mechanisms involving copper fluorides or copper silicides as active intermediates.

Kinetics and mechanism of the osmium-tetroxide-catalysed oxidation of mandelate ion by hexacyanoferrate(III) ion

1968 ◽  
Vol 21 (12) ◽  
pp. 2913 ◽  
Author(s):  
NP Singh ◽  
VN Singh ◽  
MP Singh
Keyword(s):  
Benzoic Acid ◽  
Oxidation Product ◽  
Osmium Tetroxide ◽  
Reaction Rate ◽  
Zero Order ◽  
Ion Concentration ◽  
First Order ◽  
First Order Kinetics ◽  
Catalysed Oxidation ◽  
Hydroxyl Ion

The osmium-tetroxide-catalysed oxidation of mandelate ion by hexacyanoferrate(111) ion has been studied kinetically. The reaction rate has been found to be independent of hexacyanoferrate(111) ion while the order with respect to both osmium tetroxide and mandelate ion comes out to be unity. The reaction rate follows first-order kinetics at low hydroxyl ion concentration and becomes zero order at higher concentrations. The course of the reaction has been considered to proceed through the formation of an activated mandelate-OsO4, complex which decomposes in alkaline medium giving reduced osmium(V1) followed by a fast oxidation by hexacyanoferrate(111) ion. The probable course of the reactions is also described with the help of its oxidation product, benzoic acid.

scholarly journals Kinetic intermediates of unfolding of dimeric prostatic phosphatase.

2007 ◽  
Vol 54 (2) ◽  
pp. 371-377
Author(s):  
Radosława Kuciel ◽  
Aleksandra Mazurkiewicz ◽  
Paulina Dudzik
Keyword(s):  
Rate Constants ◽  
Congo Red ◽  
Reaction Rate ◽  
Enzyme Inactivation ◽  
Thiol Groups ◽  
Ans Binding ◽  
First Order ◽  
Activity Measurements ◽  
Catalytically Active ◽  
Pseudo First Order

Kinetics of guanidine hydrochloride (GdnHCl)-induced unfolding of human prostatic acid phosphatase (hPAP), a homodimer of 50 kDa subunit molecular mass was investigated with enzyme activity measurements, capacity for binding an external hydrophobic probe, 1-anilinonaphtalene-8-sulfonate (ANS), accessibility of thiols to reaction with 5,5'-dithiobis(2-nitrobenzoic acid) (DTNB) and 2-(4'-maleimidylanilino)naphthalene-6-sulfonate (MIANS) and ability to bind Congo red dye. Kinetic analysis was performed to describe a possible mechanism of hPAP unfolding and dissociation that leads to generation of an inactive monomeric intermediate that resembles, in solution of 1.25 M GdnHCl pH 7.5, at 20 degrees C, in equilibrium, a molten globule state. The reaction of hPAP inactivation in 1.25 M GdnHCl followed first order kinetics with the reaction rate constant 0.0715 +/- 0.0024 min(-1) . The rate constants of similar range were found for the pseudo-first-order reactions of ANS and Congo red binding: 0.0366 +/- 0.0018 min(-1) and 0.0409 +/- 0.0052 min(-1), respectively. Free thiol groups, inaccessible in the native protein, were gradually becoming, with the progress of unfolding, exposed for the reactions with DTNB and MIANS, with the pseudo-first-order reaction rate constants 0.327 +/- 0.014 min(-1) and 0.216 +/- 0.010 min(-1), respectively. The data indicated that in the course of hPAP denaturation exposure of thiol groups to reagents took place faster than the enzyme inactivation and exposure of the protein hydrophobic surface. This suggested the existence of a catalytically active, partially unfolded, but probably dimeric kinetic intermediate in the process of hPAP unfolding. On the other hand, the protein inactivation was accompanied by exposure of a hydrophobic, ANS-binding surface, and with an increased capacity to bind Congo red. Together with previous studies these results suggest that the stability of the catalytically active conformation of the enzyme depends mainly on the dimeric structure of the native hPAP.

scholarly journals Occurrence and Some Characterization Studies of Invertase in the Green Plantain Fruit (Musa parasidiaca)

1969 ◽  
Vol 46 (2) ◽  
pp. 120-126
Author(s):  
Betty G. García
Keyword(s):  
Crude Protein ◽  
Reaction Rate ◽  
Order Reaction ◽  
Zero Order ◽  
Optimum Temperature ◽  
First Order ◽  
Sucrose Solutions ◽  
Optimum Ph ◽  
Characterization Studies ◽  
Substrate Concentrations

The crude-protein fraction of green plantains was isolated and found to cause an inversion of sucrose solutions. The rate of inversion of sucrose by the invertase of the green plantain is proportional to the concentration of enzyme. The inversion of sucrose, when catalyzed by green-plantain invertase, appears to follow a first-order reaction rate at low substrate concentrations (below 6 percent). As the concentration of sucrose exceeds 6 percent the rate of the reaction changes to zero order. An optimum pH of 4.15 and an optimum temperature of 44.4° C. were obtained for the activity of green-plantain invertase.

Rhodium(I) catalyzed E/Z isomerization of dimethyl butenedioate

1985 ◽  
Vol 50 (6) ◽  
pp. 1274-1282 ◽  
Author(s):  
Jaroslav Podlaha ◽  
Miloš Procházka
Keyword(s):  
Experimental Evidence ◽  
Triphenylphosphine Oxide ◽  
Active Species ◽  
Equimolar Mixture ◽  
Rhodium Complexes ◽  
Hydride Complexes ◽  
High Substrate ◽  
First Order ◽  
Highly Effective ◽  
Catalytically Active

Hydride complexes of Rh(I) represent highly effective homogeneous catalysts of the isomerization of (Z)-dimethyl butenedioate (I) yielding (E)-dimethyl butenedioate (II) in benzene at 25 °C. The reaction catalyzed by RhH(P(C6H5)3)4 is first order both in I and in the catalyst, k = 0.51 l mol-1 s-1, Ea = 48 kJ mol-1, ΔS≠ = -46 J mol-1 K-1. At high substrate-to-catalyst ratios the catalyst is inactivated, which consists mainly in deoxygenation and decarbonylation of the E- and Z-esters with formation of methyl 2-butenoate, triphenylphosphine oxide, and carbonylocomplexes of Rh(I). Statistical redistribution of deuterium during the isomerization of equimolar mixture of I and [2,3-2H2]-I and other experimental evidence are consistent with the addition-elimination hydride mechanism of the isomerization involving σ-alkyl rhodium complexes as the intermediates and RhH(P(C6H5)3)2 as the catalytically active species.

Mechanism of Hg(II) Oxidation of D-Galactose in Alkaline Medium

1978 ◽  
Vol 33 (6) ◽  
pp. 657-659 ◽  
Author(s):  
M. P. Singh ◽  
A. K. Singh ◽  
Mandhir Kumar
Keyword(s):  
Alkaline Medium ◽  
Reaction Rate ◽  
Reducing Sugar ◽  
Zero Order ◽  
Ion Concentration ◽  
Kinetics Of Oxidation ◽  
Ion Concentrations ◽  
First Order ◽  
Kinetics Of ◽  
Direct Proportionality

Abstract The present paper deals with the kinetics of oxidation of D-galactose by Nessler's reagent in alkaline medium. The reaction is zero order with respect to Hg(II) and first order with respect to reducing sugar. The direct proportionality of the reaction rate at low hydroxide ion concentrations shows retarding trend at higher concentrations. The reaction rate is inversely proportional to iodide ion concentration. A mechanism has been proposed taking HgI3- as the reacting species

Mechanism of the oxidation of triphenyl derivatives of P, As, and Sb by peroxodiphosphate

1985 ◽  
Vol 63 (8) ◽  
pp. 2285-2289 ◽  
Author(s):  
C. Srinivasan ◽  
K. Pitchumani
Keyword(s):  
Ionic Strength ◽  
Reaction Rate ◽  
Relative Rate ◽  
Active Species ◽  
Second Order ◽  
Rate Coefficients ◽  
General Mechanism ◽  
First Order ◽  
Nucleophilic Displacement ◽  
Derivatives Of

Rate coefficients have been determined for the oxidation of Ph3M (M = P, As, Sb) by potassium peroxodiphosphate. The reaction is found to follow second-order kinetics, first order in each in the oxidant and Ph3M. [H+] has a pronounced accelerating effect on the reaction rate. An interesting dependence of the active species on the nature of the substrate has been observed. The reaction rate is influenced by changing the ionic strength of the medium. Acrylonitrile has no effect on the rate of oxidation. On the basis of the kinetic evidence, a general mechanism involving a biomolecular nucleophilic displacement of the substrate on the peroxo ion has been proposed. The relative rate order is found to be Ph3P > Ph3Sb > Ph3As and an explanation has been offered for the transposition of Ph3Sb and Ph3As.

The uncatalysed, and the imidazole and o-mercaptobenzoic acid catalysed, hydrolysis of p-nitrophenyl N-benzyloxycarbonylglycinate

1969 ◽  
Vol 22 (1) ◽  
pp. 109 ◽  
Author(s):  
RW Hay ◽  
RJ Trethewey
Keyword(s):  
Active Species ◽  
Ion Concentration ◽  
Nucleophilic Catalysis ◽  
First Order ◽  
Catalysed Reaction ◽  
Catalytically Active ◽  
Ph Range ◽  
Rapid Hydrolysis ◽  
Rate Profile ◽  
Hydrolysis Of

The uncatalysed hydrolysis of p-nitrophenyl N- benzyloxycarbonylglycinate has been studied in 40% (v/v) ethanol-water over the pH range 7.6-8.5. The reaction shows a first-order dependence on the hydroxide ion concentration. The quite rapid hydrolysis (k = (4.4�0.4) x 104 1. mole-1 min-1 at 20�) may possibly indicate the formation of a 2-benzyloxyoxazoline-5-one intermediate. ��� Unlike the hydrolysis of the p-nitrophenyl esters of α-amino acids, the hydrolysis of the N-protected derivatives is not catalysed by carbon dioxide. The hydrolysis of p-nitrophenyl N- benzyloxycarbonylglycinate is, however, catalysed by imidazole in 40% v/v ethanol-water. Unprotonated imidazole (Im) is the catalytically active species. N-Benzyloxycarbonylaminoacetylimidazole has been detected spectrophotometrically as an intermediate in the reaction, indicating nucleophilic catalysis by the base. o-Mercaptobenzoic acid was also found to catalyse the hydrolysis of p-nitrophenyl N- benzyloxycarbonylglycinate. pH-rate profile studies indicate that the dianion of o-mercaptobenzoic acid is the catalytically active species, the substrate presumably hydrolysing via the thioester intermediate Z- NHCH2COSC6H4COO-, although efforts to detect such an intermediate have been unsuccessful. Some evidence for a thioester intermediate in the L- cysteine-catalysed reaction has been obtained.

scholarly journals Kinetics and Mechanism of Oxidation of Malic Acid by N-Bromonicotinamide (NBN) in the Presence of a Micellar System

2015 ◽  
Vol 52 ◽  
pp. 111-119
Author(s):  
L. Pushpalatha
Keyword(s):  
Malic Acid ◽  
Reaction Rate ◽  
Activation Parameters ◽  
Zero Order ◽  
Micellar System ◽  
First Order ◽  
First Order Kinetics ◽  
Rate Of Reaction ◽  
Different Temperatures ◽  
Experimental Findings

The oxidation of malic acid by N-bromonicotinamide in the presence of micellar system is studied. First order kinetics with respect to NBN is observed. The kinetics results indicate that the first order kinetics in hydroxy acid at lower concentrations tends towards a zero order at its higher concentrations. Inverse fractional order in [H+] and [nicotinamide] are noted throughout its tenfold variation. Variation of [Hg (OAc)2] and ionic strength of the medium do not bring about any significant change in the rate of reaction. Rate of the reaction increases with a decrease in the percentage of acetic acid. Decrease in the rate constant was observed with the increase in [SDS]. The values of rate constants observed at four different temperatures were utilized to calculate the activation parameters. A suitable mechanism consistent with the experimental findings has been proposed.

Rate of reaction of dithionite ion with oxygen in aqueous solution

1964 ◽  
Vol 19 (3) ◽  
pp. 522-525 ◽  
Author(s):  
J. A. Morello ◽  
Margot R. Craw ◽  
H. P. Constantine ◽  
R. E. Forster
Keyword(s):  
Aqueous Solution ◽  
Reaction Rate ◽  
Initial Rate ◽  
Sodium Dithionite ◽  
Zero Order ◽  
Flowing Liquid ◽  
First Order ◽  
Rate Of Reaction ◽  
Dithionite Ion ◽  
Kinetics Of

The rate of removal of oxygen from aqueous solution by sodium dithionite in 0.1 m sodium hydroxide was studied in a rapid-reaction apparatus using a membrane-covered polarographic cell to determine Po2 in the flowing liquid. The measurements were made at 37 C, so that the data would be applicable in studies of the kinetics of oxyhemoglobin in blood. The initial concentrations in the mixed reacting solution were between 8 x 10-5 m and 47.5 x 10-5 m for dithionite, and either 10 x 10-5 m or 47.8 x 10-5 m for O2. The reaction over the first 40 msec was found to be first order with respect to dithionite and zero order with respect to molecular oxygen. The initial rate constant was 42.5 ± sd 3.6 sec-1. oxygen reduction by dithionite; hemoglobin; deoxygenation rate; dithionite-oxygen reaction rate Submitted on June 17, 1963

scholarly journals Catalytically Active Gold Nanoparticles Synthesized using Diabetic Sugar Via Rapid, Simple, Greener Process

2019 ◽  
Vol 35 (5) ◽  
pp. 1519-1528
Author(s):  
Nurdiani Nurdiani ◽  
Foliatini Foliatini
Keyword(s):  
Reaction Rate ◽  
Au Nanoparticles ◽  
Colloidal Solution ◽  
Oxidation Process ◽  
Infrared Spectrophotometry ◽  
Pseudo First Order Reaction ◽  
First Order ◽  
Catalytically Active ◽  
Kinetics Of ◽  
Hydrolysis Of

Au nanoparticles were successfully synthesized using diabetic sugar as reducing agent, with and without the aid of microwave heating. The hydrolysis of diabetic sugar was carried out using HCl, prior to the synthesis. By adjusting pH of the mixture to basic condition, the formation of the nanoparticles effectively occurred resulting purple colloidal solution. The solution was centrifuged or left overnight to yield precipitate of Au nanoparticles. The as-formed Au nanoparticles were characterized by UV-Vis spectrophotometry, Fourier-Transform infrared spectrophotometry and scanning electron microscopy. The result showed that the Au nanoparticles played a significant role as catalyst for oxidation of methylene blue by H2O2. The kinetics of the oxidation process followed pseudo first order reaction rate with the rate constant depending on the AuNP characteristic and experimental condition.

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