The Oxidation of Benzyldimethylamine by Bromine

1973 ◽  
Vol 51 (15) ◽  
pp. 2546-2554 ◽  
Author(s):  
Donald G. Lee ◽  
R. Srinivasan
Keyword(s):  
Acetic Acid ◽  
Hydrogen Atom ◽  
Base Catalysis ◽  
Slow Step ◽  
Aqueous Acetic Acid ◽  
General Base ◽  
Rate Determining Step ◽  
Rate Of Reaction ◽  
Electron Withdrawing Substituents

The rates of oxidation of several substituted benzyldimethylamines by bromine in 50% aqueous acetic acid have been determined spectrophotometrically. Electron-withdrawing substituents decrease the rate of reaction with the Hammett ρ value being −0.95. The reaction is subject to general base catalysis and substitution of deuterium in the α-position decreases the rate of reaction by approximately 30%, thus indicating that the α-C—H bond is cleaved in the slow step of the reaction. All results are consistent with a mechanism which involves, in the rate determining step, loss of an α-hydrogen atom as a proton with concomitant transfer of electrons from nitrogen to the oxidant.

scholarly journals Kinetics and mechanism of the Oxidative regeneration of Carbonyl Compounds from Phenylhydrazones by Tetramminecopper(2+) Bis (Permanganate)

2003 ◽  
Vol 2003 (4) ◽  
pp. 184-185
Author(s):  
Raghvendra Shukla ◽  
László Kótai ◽  
Pradeep K. Sharma ◽  
Kalyan K. Banerji
Keyword(s):  
Acetic Acid ◽  
Carbonyl Compounds ◽  
Kinetics And Mechanism ◽  
Aqueous Acetic Acid ◽  
Acid Proceeds ◽  
Oxidative Regeneration ◽  
Rate Determining Step ◽  
Activated Complex

The oxidation of aldo- and keto-phenylhydrazones by tetraamminecopper(2+) bis(permanganate) (TACP), in aqueous acetic acid, proceeds through a mechanism involving the formation of a cyclic activated complex, in the rate-determining step.

scholarly journals Kinetics of Oxidation of Some Amino Acids by N-Chlorosaccharin in Aqueous Acetic Acid Medium

2004 ◽  
Vol 1 (2) ◽  
pp. 127-131 ◽  
Author(s):  
N. A. Mohamed Farook ◽  
R. Prabaharan ◽  
S. Rahini ◽  
R. Senthil Kumar ◽  
G. Rajamahendran ◽  
...  
Keyword(s):  
Amino Acids ◽  
Acetic Acid ◽  
Acid Medium ◽  
Hypochlorous Acid ◽  
Activation Parameters ◽  
Slow Step ◽  
Aqueous Acetic Acid ◽  
Acetic Acid Medium ◽  
Kinetics Of Oxidation ◽  
Kinetics Of

The kinetics of oxidation of some amino acids namely, glycine, alanine, aspartic acid, arginine, and histidine, (AA) byN-chlorosaccharin (NCSA) in aqueous acetic acid medium in the presence of perchloric acid have been investigated. The observed rate of oxidation is first order in [AA], [NCSA] and of inverse fractional order in [H+]. The main product of the oxidation is the corresponding aldehyde. The ionic strength on the reaction rate has no significant effect. The effect of changing the dielectric constant of the medium on the rate indicates the reaction to be of dipole-dipole type. Hypochlorous acid has been postulated as the reactive oxidizing species. The reaction constants involved in the mechanism are derived. The activation parameters are computed with respect to slow step of the mechanism.

scholarly journals Kinetics of Oxidation of 3-Benzoylpropionic Acid byN-Chlorobenzamide in Aqueous Acetic Acid Medium

2011 ◽  
Vol 8 (2) ◽  
pp. 561-564 ◽  
Author(s):  
N. A. Mohamed Farook ◽  
G. A. Seyed Dameem
Keyword(s):  
Acetic Acid ◽  
Acid Medium ◽  
Reaction Medium ◽  
Activation Parameters ◽  
Slow Step ◽  
Aqueous Acetic Acid ◽  
Acetic Acid Medium ◽  
Kinetics Of Oxidation ◽  
First Order ◽  
Kinetics Of

The kinetics of oxidation of 3-benzoylpropionic acid(KA)byN-chlorobenzamide(NCB)in aqueous acetic acid medium in the presence of perchloric acid have been investigated. The observed rate of oxidation is first order dependence each in[KA],[NCB]and [H+]. The main product of the oxidation is the corresponding carboxylic acid. The rate decreases with the addition of benzamide, one of the products of the reaction. Variation in ionic strength of the reaction medium has no significant effect on the rate of oxidation. But the rate of the reaction is enhanced by lowering the dielectric constant of the reaction medium. Hypochlorous acidium ion (H2O+Cl), has been postulated as the reactive oxidizing species. A mechanism consistent with observed results have been proposed and the related rate law deduced. The activation parameters have been computed with respect to slow step of the mechanism.

scholarly journals Kinetics of Oxidation of Some Essential Amino Acids by N-Chlorosaccharin in Aqueous Acetic Acid Medium

2004 ◽  
Vol 1 (2) ◽  
pp. 132-136 ◽  
Author(s):  
N. A. Mohamed Farook ◽  
G. A. Seyed Dameem ◽  
A. Murugesan ◽  
M. Kanagaraj
Keyword(s):  
Amino Acids ◽  
Acetic Acid ◽  
Acid Medium ◽  
Hypochlorous Acid ◽  
Essential Amino Acids ◽  
Slow Step ◽  
Aqueous Acetic Acid ◽  
Acetic Acid Medium ◽  
Kinetics Of Oxidation ◽  
Kinetics Of

The kinetics of oxidation of some essential amino acids namely, valine, leucine and phenylalanine, (AA) byN-chlorosaccharin (NCSA) in aqueous acetic acid medium in the presence of perchloric acid have been investigated. The observed rate of oxidation is first order in [AA], [NCSA] and of inverse fractional order in [H+]. The main product of the oxidation is the corresponding aldehyde. The ionic strength on the reaction rate has no significant effect. The effect of changing the dielectric constant of the medium on the rate indicates the reaction to be of dipole-dipole type. Hypochlorous acid has been postulated as the reactive oxidizing species. The reaction constants involved in the mechanism are derived. The activation parameters are computed with respect to slow step of the mechanism

Multiple changes in rate-determining step in the acid and base catalyzed cyclizations of ethyl N-(p-nitrophenyl)hydantoates caused by methyl substitution

1999 ◽  
Vol 77 (5-6) ◽  
pp. 849-859
Author(s):  
Iva B Blagoeva ◽  
Anthony J Kirby ◽  
Asen H Koedjikov ◽  
Ivan G Pojarlieff
Keyword(s):  
Steric Hindrance ◽  
Acid Catalysis ◽  
Isotope Effects ◽  
Base Catalysis ◽  
Ethoxy Group ◽  
First Order ◽  
Tetrahedral Intermediate ◽  
General Base ◽  
Rate Determining Step ◽  
Acid And Base

The slopes of the pH-rate profiles for the cyclization of 2-methyl- and 2,3-dimethyl hydantoates 1-NPU and 2-NPU between pH 1 and 7 change from 1 to 0 and then back to 1. A reaction first order in H+ was observed with the latter compound. The 2,2,3-trimethyl derivative 3-NPU showed only one reaction first order in OH-, but complex acid catalysis is described by slopes 0, -1, 0, and finally -1 again. The cyclizations were general base catalyzed, with Brønsted β values of 0.5-0.6. The OH- catalysis at higher pH for 1-NPU and 2-NPU showed inverse solvent kinetic isotope effects and deviated from the Brønsted relationships, while that for 3-NPU showed a normal effect and complied with the Brønsted relationship. The accelerations due to the gem-dimethyl effect were lost with the OH- and general base-catalyzed reactions of 3-NPU. This behaviour is due to a change from the rate-determining formation of the tetrahedral intermediate with 1-NPU and 2-NPU to the rate-determining breakdown with 3-NPU, due to steric hindrance to protonation of the leaving ethoxy group. The OH- reaction at higher pH involves attack of the ureide anion with 1-NPU and 2- NPU, becoming concerted with deprotonation when catalyzed by general bases and changing to acid inhibition of the anion of the tetrahedral intermediate at low pH. With 3-NPU at higher pH, T- is in equilibrium and the conjugate acids of the general bases accelerate its breakdown by protonating the ethoxy group. Acid catalysis of the cyclization of 3-NPU at higher pH is also protonation of the leaving group from T0 changing to the rate-determining formation of T at lower pH. The latter mechanism is preferred for the cyclization of 2-NPU.Key words: gem-dimethyl effect, mechanism, general base catalysis, proton transfer, steric hindrance.

A kinetic study of the chlorination of ketones by chloramine-T: Novel concentration dependences on the chlorinating agent and the ketones

1976 ◽  
Vol 29 (7) ◽  
pp. 1449 ◽  
Author(s):  
V Balasubramanian ◽  
V Thiagarajan
Keyword(s):  
Acetic Acid ◽  
Kinetic Study ◽  
Acidic Medium ◽  
Aqueous Acetic Acid ◽  
Acetic Acid Medium ◽  
Rate Determining Step ◽  
Low Concentrations ◽  
Concentration Dependences ◽  
Chloramine T ◽  
High Concentrations

The chlorination of acetone in aqueous acidic medium in the presence of acetic acid and dimethylformamide was subjected to kinetic study. Although the kinetics follows the traditional mechanism at high concentrations of chloramine-T (cat) and in aqueous acetic acid in the presence of sodium acetate, a term in the rate law independent of ketone concentration is reported for the first time in strongly acidic medium at low concentrations of chloramine-T. Generation of the chlorinating species is considered as the rate-determining step (Scheme 1). The mechanistic changes which occur on addition of chloride and on changing the structure of the ketone are reported. The effect of acetate on the rate in aqueous acetic acid medium is rationalized by invoking a prior equilibrium formation of enolate followed by a rate-controlling chlorination by chlorinium acetate. The retardation in rate and the consequent changes in mechanism in the case of p-bromo- and p-nitroacetophenone are accounted for by invoking a complex between the enol and the positive chlorine species similar to that in the mechanism for the chlorination of phenols.

Chlorination of N-Phenylbenzenesulfonamides with NCP in Aqueous Acetic Acid. Using the para/meta Ratio of Substituent Effects for Mechanism Elucidation

2004 ◽  
Vol 69 (12) ◽  
pp. 2253-2275 ◽  
Author(s):  
João Carlos R. Reis ◽  
Manuel A. P. Segurado ◽  
Jaime D. Gomes de Oliveira ◽  
Senthamaraikannan Kabilan ◽  
Krishnasamy Suganya
Keyword(s):  
Acetic Acid ◽  
Nitrogen Atom ◽  
Rate Constants ◽  
Substituent Effects ◽  
Aqueous Acetic Acid ◽  
Isokinetic Temperature ◽  
Isokinetic Relationship ◽  
Rate Determining Step ◽  
Different Temperatures ◽  
Energy Ratios

Rate constants were measured for the oxidative chlorination reaction of N-phenylbenzenesulfonamide 2 and twelve ortho-, nine meta- and twelve para-substituted derivatives in the aniline moiety, using 1-chloro-3-methyl-2,6-diphenylpiperidin-4-one (1) as chlorinating agent. The kinetics was run in 50% (v/v) aqueous acetic acid acidified with perchloric acid under pseudo-first-order conditions with respect to 1 at five different temperatures between 298 and 318 K. The dependence of rate constants on temperature was analysed in terms of the isokinetic relationship (IKR). The resulting isokinetic temperature was estimated to be 513 K. Using the Linert's theory of the IKR, the experimental isokinetic temperature was interpreted as evidence for the preferential involvement of water molecules in the formation of activated complexes. The dependence of the rate constants on the substituents was analysed using the tetralinear extension of the Yukawa-Tsuno equation for the effects of meta and para substituents. A positively charged transition state was suggested by an experimental value r+ = 0.39 for the resonance demand, which was found to be insensitive to temperature variation. The parameter λ for the para/meta ratio of substituent effects was estimated to be 0.952. The electrostatic modelling of λ values was re-examined in the light of the recent calculations of the energies of interaction between charged and/or dipolar groups by Exner and Böhm. Based on energy ratios, the electrostatic method was shown to remain valid for the purpose of modelling λ values. The experimental λ value for the reaction indicates the formation of an activated complex possessing an electric charge in the vicinity of the nitrogen atom of the substrate. The electrophilic attack on the substrate nitrogen atom by the protonated chlorinating reagent has been proposed as the rate-determining step, with the last step being the fast rearrangement of the intermediate N-chloro-N-phenylbenzenesulfonamidium cation into the products.

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