Phosphoryl to carbonyl migration of amino groups in mixed anhydrides

1986 ◽  
Vol 64 (9) ◽  
pp. 1702-1708 ◽  
Author(s):  
Jill Symes ◽  
Tomasz A. Modro
Keyword(s):  
Transition State ◽  
Lewis Acids ◽  
Reaction Rate ◽  
Functional Group ◽  
Substituent Effects ◽  
Activation Parameters ◽  
Amino Group ◽  
Amino Groups ◽  
Group Transfer ◽  
Mixed Anhydrides

Mixed anhydrides derived from carboxylic and amidophosphoric acids, (RO)(R′2N)P(O)OC(O)R″ (1), undergo unimolecular fragmentation yielding carboxyamides, R″C(O)NR′2, and metaphosphate esters, ROPO2. The mechanism of the amino group transfer was studied for substrate 1a (1, R = R′ = Me; R″ = Ph); solvent as well as substituent effects indicate little (if any) charge development in the transition state. The effects of solvents and Lewis acids on the reaction rate and the activation parameters determined for 1a can be explained best in terms of stabilizing interactions with either carboxyamide or metaphosphate being formed in the course of reaction. The transfer of a functional group from one acyl center to another was investigated for other anhydride systems and the relative contributions of the fragmentation vs. disproportionation of substrates are discussed.

Nucleophilic cleavage of diaryl disulphides

1973 ◽  
Vol 26 (1) ◽  
pp. 121 ◽  
Author(s):  
DAR Happer ◽  
JW Mitchell ◽  
GJ Wright
Keyword(s):  
Transition State ◽  
Reaction Rate ◽  
Substituent Effects ◽  
Butyl Alcohol ◽  
Sulphur Atom ◽  
Cyanide Ion ◽  
Benzene Rings ◽  
Nucleophilic Cleavage ◽  
Rapid Equilibrium ◽  
Electron Withdrawal

The rates of cleavage of 14 symmetrically substituted diaryl disulphides by cyanide ion have been measured in 60% aqueous t-butyl alcohol at pH 9.2. A plot of log k against σ� shows that while the reaction rate is accelerated by inductive electron withdrawal from the benzene rings, substituents capable of conjugative interaction are not correlated by their σ� parameters. +R substituents cause reaction to occur much faster than predicted on the basis of their σ� values, while -R substituents react more slowly than predicted. Measurement of rates of cleavage of three series of unsymmetrically substituted disulphides by cyanide or hydroxide shows that these unusual substituent effects arise from substituents in the thiocyanate-forming aryl ring. This behaviour is explained in terms of a change in the electronic behaviour of the thio- cyanate-forming sulphur atom from -I, + R in the disulphide to -I,-R in the rate-determining transition state for the reaction. The study does not show whether the cleavage involves an SN2 process or rapid equilibrium formation of a pentacovalent intermediate.

THE KINETICS OF AMINO GROUP TRANSFER BY CORN RADICLE TRANSAMINASE

1957 ◽  
Vol 35 (12) ◽  
pp. 1289-1303 ◽  
Author(s):  
F. S. Cook
Keyword(s):  
Classical Theory ◽  
Spectrophotometric Method ◽  
Substrate Concentration ◽  
Enzyme Preparation ◽  
Reaction Rate ◽  
Amino Group ◽  
Group Transfer ◽  
Kinetics Of ◽  
Published Account

The kinetics of transamination are complicated by the presence of two substrates whose concentrations change appreciably during the course of the reaction. The only previously published account of the kinetics of this system deviates considerably from classical theory. Equations based on premises of Michaelis and Menten have been shown, however, to accommodate the data on reaction rate in relation to substrate concentration obtained with a corn radicle enzyme preparation by a spectrophotometric method.

Functional-group and substituent effects, both steric and electronic, upon the ultraviolet absorption spectra of some conjugated heteroenoid compounds

1967 ◽  
Vol 45 (13) ◽  
pp. 1567-1580 ◽  
Author(s):  
D. J. Currie ◽  
C. E. Lough ◽  
R. F. Silver ◽  
H. L. Holmes
Keyword(s):  
Functional Group ◽  
Inductive Effect ◽  
Substituent Effects ◽  
Wavelength Region ◽  
Steric Effects ◽  
Electronic Effects ◽  
Amino Groups ◽  
Empirical Parameter ◽  
Long Wavelength ◽  
Constant E

The positions of the long-wavelength maxima in the spectra of some 300 compounds of generalized formula I may be accommodated by assuming that the observed maximum is equal to that of styrene + Δλ (the conjugative effect of A) + Δλ′ (the inductive effect of B) + ΣΔλ″ (the sum of the steric effects of the A, B, and phenyl groups) + D (an empirical parameter related to X and Y). These arguments have been extended to the spectra of II. Δλ′ is related to the σ value for meta-substituted benzene derivatives or to σ*. D for meta- and [Formula: see text]para-substituted derivatives roughly correlates with the appropriate σ+ values, whereas D for ortho-substituted derivatives is related to a simple function involving the D value for para substitution and the steric substituent constant, ES. For compounds of generalized formula III, the electronic effects of the A and B groups cancel but the steric effects are additive.Multiple bands occur in the long-wavelength region of the spectra for compounds containing halogen, alkoxy, or amino groups. These groups are highly polarizable and are considered to function both as electron donors and electron sinks.

Thermolysis of 5,5-dimethyl-4-aryl-Δ1-1,2,4-triazolin-3-ones in solution. Products, kinetics, substituent effects, and solvent effects

1981 ◽  
Vol 59 (1) ◽  
pp. 100-105 ◽  
Author(s):  
Lubomira M. Cabelkova-Taguchi ◽  
John Warkentin
Keyword(s):  
Transition State ◽  
Solvent Effects ◽  
Charge Separation ◽  
Substituent Effects ◽  
Activation Parameters ◽  
Oxidative Cyclization ◽  
First Order ◽  
Temperature Range ◽  
Aryl Amine ◽  
First Order Kinetics

A series of 5,5-dimethyl-4-aryl-Δ1-1,2,4-triazolin-3-ones (Ar = C6H5, p-C6H4CH3, p-C6H4OCH3, p-C6H4Cl, and p-C6H4Br) were prepared from the corresponding 4-arylsemicarbazones of acetone by oxidative cyclization on alumina. The triazolinones decompose in solution to N2, CO, and isopropylidene aryl amine, with first order kinetics, in the temperature range 148–200 °C. Average activation parameters are ΔH≠ = 35 kcal mol−1 and ΔS≠ = 8 cal K−1 mol−1. Substituent effects are correlated through σ-constants but the thermolyses are relatively insensitive to substituents, with ρ = −0.17 at 172.5 °C. Solvent effects indicate a transition state that is less polar than the ground state.It is tentatively concluded that the triazolinone fragmentation, like the analogous thermolysis of a Δ3-1,3,4-oxadiazolin-2-one, may be a fully-concerted but nonsynchronous process with a transition state involving little, if any, charge separation. Other mechanisms, except for those involving highly polar (e.g. zwitterionic) transition states, have not been ruled out.

scholarly journals Reactivity of Microcrystalline Cellulose with Methyltrimethoxysilane and 3-(2-Aminoethylamino) propyltrimethoxysilanes

2021 ◽  
Vol 68 (4) ◽  
pp. 849-860
Author(s):  
Przemysław Pietras ◽  
Hieronim Maciejewski ◽  
Bartłomiej Mazela
Keyword(s):  
Microcrystalline Cellulose ◽  
Functional Group ◽  
Chemical Reactivity ◽  
Pure Water ◽  
Model Material ◽  
Amino Group ◽  
Silane Treatment ◽  
Natural Polymers ◽  
Amino Groups ◽  
Cellulose Modification

In the presented research, two trialkoxysilanes were used to investigate their reactivity with microcrystalline cellulose (MCC) applied as a model material. As a continuation of the previous study, the research aimed at evaluation of the durability and potential reversibility of the silane treatment. Two different solvents and a mixture thereof were used for cellulose modification. The influence of amino group/pH, an excess of silanes and re-soaking with water on binding with cellulose was examined. The results obtained confirm that both selected silanes can effectively modify MCC. However, the treatment with 3-(2-aminoethylamino)propyltrimethoxysilane occurred more effective than with Methyltrimethoxysilane due to the presence of amino groups. Among the three tested solvents, the most effective was pure water. In contrast, the use of ethanol and a mixture of ethanol and water gave significantly worse results. Summarising, the presented research clearly shows how important the type of the functional group in alkoxysilanes is for its chemical reactivity with natural polymers, which is crucial for their application in waterlogged wood conservation.

THE KINETICS OF AMINO GROUP TRANSFER BY CORN RADICLE TRANSAMINASE

1957 ◽  
Vol 35 (1) ◽  
pp. 1289-1303 ◽  
Author(s):  
F. S. Cook
Keyword(s):  
Classical Theory ◽  
Spectrophotometric Method ◽  
Substrate Concentration ◽  
Enzyme Preparation ◽  
Reaction Rate ◽  
Amino Group ◽  
Group Transfer ◽  
Kinetics Of ◽  
Published Account

The kinetics of transamination are complicated by the presence of two substrates whose concentrations change appreciably during the course of the reaction. The only previously published account of the kinetics of this system deviates considerably from classical theory. Equations based on premises of Michaelis and Menten have been shown, however, to accommodate the data on reaction rate in relation to substrate concentration obtained with a corn radicle enzyme preparation by a spectrophotometric method.

Kinetics and mechanism of redox reactions of U(III) ions with monochloroacetic and dichloroacetic acids

1979 ◽  
Vol 44 (2) ◽  
pp. 401-405 ◽  
Author(s):  
Ľubica Adamčíková ◽  
Ľudovít Treindl
Keyword(s):  
Redox Reactions ◽  
Reaction Rate ◽  
Activation Parameters ◽  
Outer Sphere ◽  
Alcohol Concentration ◽  
Kinetics And Mechanism ◽  
Solvent Structure ◽  
Influence Of Ph ◽  
Sphere Mechanism

The kinetics and mechanism of the redox reactions of U3+ ions with mono- and dichloroacetic acids were studied. The influence of pH was observed mainly in the second case and led to the determination of the rate constants and activation parameters corresponding to two parallel steps, namely oxidation of U3+ with CHCl2COO- ions and oxidation of U3+ with CHCl2.COOH molecules. The influence of binary mixtures of water with methanol, ethanol, isopropanol, or tert-butenol on the reaction rate was followed. Increasing alcohol concentration influences the rate constant not only through changing dielectric constant and solvation of the reactants but also through a change of the solvent structure which plays a role in reactions with an outer sphere mechanism of the electron transfer.

Substituent Effects on the Basicity of ortho-, meta- and para-substituted N1,N1-Dimethyl-N2-phenylformamidines in Ethanol and in Water

1992 ◽  
Vol 57 (1) ◽  
pp. 113-118
Author(s):  
Ewa Daniela Raczyńska
Keyword(s):  
Quantitative Analysis ◽  
Aqueous Ethanol ◽  
Substituent Effects ◽  
Amino Group

The relative δpKa values of ortho-, meta-, and para-substituted N1,N1-dimethyl-N2-phenylformamidines obtained in 95.6% aqueous ethanol have been compared with those in water. The comparison shows only some differences in the ortho substituent effects. The meta and para substituent effects in ethanol are not very different from those in water. Quantitative analysis of the experimental δpKa values based on the Taft equation has led to separation of the total electromeric effects into the inductive and mesomeric effects. As compared to the amino group in anilines, the formamidine group is more sensitive to the transmission of the inductive than the mesomeric effects.

Investigation of the effect of ring size on the product distribution for the Schiff base reaction of 2-acetylcycloalkanones with diamino alkanes

1995 ◽  
Vol 73 (1) ◽  
pp. 16-21 ◽  
Author(s):  
Raul G. Enriquez ◽  
Juan M. Fernandez-G ◽  
Ismael Leon ◽  
William F. Reynolds ◽  
Ji.-Ping Yang ◽  
...  
Keyword(s):  
Schiff Base ◽  
Condensation Reaction ◽  
2D Nmr ◽  
Product Distribution ◽  
Major Product ◽  
Ring Size ◽  
Amino Group ◽  
Amino Groups ◽  
Similar Product ◽  
Acetyl Group

The Schiff base condensation reaction of 1,2-diaminoethane with a series of 2-acetylcycloalkanones (from cyclopentanone to cyclooctanone) has been investigated and the products characterized by two-dimensional nuclear magnetic resonance. The site of attack of the amino groups, i.e., ring ketone or acetyl ketone, is determined primarily by ring size. 2-Acetylcyclohexanone yields two products in ca. 9:1 ratio, the major product where the two amino groups attack at the ring ketones of two different cyclohexanone molecules, and the minor product where one amino group attacks one ring carbonyl of one cyclohexanone while the second amino group attacks the acetyl group of another. 2-Acetylcyclopentanone yields all three possible products with the major product involving attack at the acetyl groups of two different cyclopentanones. The corresponding reactions for 2-acetylcycloheptanone and 2-acetylcyclooctanone each give a single product corresponding to attack at the acetyl groups of two different cycloalkanones. Similar product distributions are observed for the reactions of the different 2-acetylcycloalkanones with 1,4-diaminobutane. Keywords: Schiff base reactions, diketones, 2D NMR.

scholarly journals Perborate Oxidation of Substituted 5-Oxoacids in Aqueous Acetic Acid Medium: A Kinetic and Mechanistic Study

2014 ◽  
Vol 2014 ◽  
pp. 1-7 ◽  
Author(s):  
S. Shree Devi ◽  
B. Muthukumaran ◽  
P. Krishnamoorthy
Keyword(s):  
Acetic Acid ◽  
Acid Medium ◽  
Reaction Rate ◽  
Reaction Medium ◽  
Activation Parameters ◽  
Reaction Rates ◽  
Mechanistic Study ◽  
Aqueous Acetic Acid ◽  
Sodium Perborate ◽  
Acetic Acid Medium

Kinetics and mechanism of oxidation of substituted 5-oxoacids by sodium perborate in aqueous acetic acid medium have been studied. The reaction exhibits first order both in [perborate] and [5-oxoacid] and second order in [H+]. Variation in ionic strength has no effect on the reaction rate, while the reaction rates are enhanced on lowering the dielectric constant of the reaction medium. Electron releasing substituents in the aromatic ring accelerate the reaction rate and electron withdrawing substituents retard the reaction. The order of reactivity among the studied 5-oxoacids is p-methoxy ≫ p-methyl > p-phenyl > –H > p-chloro > p-bromo > m-nitro. The oxidation is faster than H2O2 oxidation. The formation of H2BO3+ is the reactive species of perborate in the acid medium. Activation parameters have been evaluated using Arrhenius and Eyring’s plots. A mechanism consistent with the observed kinetic data has been proposed and discussed. Based on the mechanism a suitable rate law is derived.

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