Kinetics of acid and nucleophile catalysis of the diazotization of 1-naphthylamine

1986 ◽  
Vol 64 (1) ◽  
pp. 133-137 ◽  
Author(s):  
Julio Casado ◽  
Albino Castro ◽  
Emilia Iglesias ◽  
M. Elena Peña ◽  
José Vázquez Tato
Keyword(s):  
Proton Transfer ◽  
Isotopic Effect ◽  
Formation Equilibria ◽  
High Concentrations ◽  
Kinetics Of ◽  
Rate Controlling Step

The diazotization of 1-naphthylamine has been studied at acidities ranging from 10−2 to 1.5 M. At low acidities nitrosation takes place via the unprotonated form of the amine, and the rate-controlling step is either the interaction with the nitrosating agent or, if high concentrations of a nucleophile are present, the loss of a proton from the protonated nitrosamine (the nucleophiles studied were Cl−, Br−, SCN−, and thiourea). At high acidities the protonated and free amines also react, the former of these reactions involving proton transfer to the solvent. In each case the proposed mechanism was supported by studying the reaction in D2O, which also allowed the isotopic effect of the solvent on the formation equilibria of the various nitrosating agents to be obtained.

scholarly journals Desensitization Contributes to the Synaptic Response of Gain-of-Function Mutants of the Muscle Nicotinic Receptor

2006 ◽  
Vol 128 (5) ◽  
pp. 615-627 ◽  
Author(s):  
Sergio Elenes ◽  
Ying Ni ◽  
Gisela D. Cymes ◽  
Claudio Grosman
Keyword(s):  
Nicotinic Receptor ◽  
Dissociation Rate ◽  
Gain Of Function ◽  
Naturally Occurring ◽  
Channel Opening ◽  
Speed Up ◽  
High Concentrations ◽  
Dissociation Rate Constants ◽  
Kinetics Of ◽  
Peak Value

Although the muscle nicotinic receptor (AChR) desensitizes almost completely in the steady presence of high concentrations of acetylcholine (ACh), it is well established that AChRs do not accumulate in desensitized states under normal physiological conditions of neurotransmitter release and clearance. Quantitative considerations in the framework of plausible kinetic schemes, however, lead us to predict that mutations that speed up channel opening, slow down channel closure, and/or slow down the dissociation of neurotransmitter (i.e., gain-of-function mutations) increase the extent to which AChRs desensitize upon ACh removal. In this paper, we confirm this prediction by applying high-frequency trains of brief (∼1 ms) ACh pulses to outside-out membrane patches expressing either lab-engineered or naturally occurring (disease-causing) gain-of-function mutants. Entry into desensitization was evident in our experiments as a frequency-dependent depression in the peak value of succesive macroscopic current responses, in a manner that is remarkably consistent with the theoretical expectation. We conclude that the comparatively small depression of the macroscopic currents observed upon repetitive stimulation of the wild-type AChR is due, not to desensitization being exceedingly slow but, rather, to the particular balance between gating, entry into desensitization, and ACh dissociation rate constants. Disruption of this fine balance by, for example, mutations can lead to enhanced desensitization even if the kinetics of entry into, and recovery from, desensitization themselves are not affected. It follows that accounting for the (usually overlooked) desensitization phenomenon is essential for the correct interpretation of mutagenesis-driven structure–function relationships and for the understanding of pathological synaptic transmission at the vertebrate neuromuscular junction.

Excited state proton transfer and photochromism of an aromatic Schiff base. Pico- and femtosecond kinetics of the N,N′-bis(salicylidene)-p-phenylenediamine (BSP)

2003 ◽  
Vol 369 (1-2) ◽  
pp. 80-89 ◽  
Author(s):  
Marcin Ziółek ◽  
Jacek Kubicki ◽  
Andrzej Maciejewski ◽  
Ryszard Naskrȩcki ◽  
Anna Grabowska
Keyword(s):  
Schiff Base ◽  
Excited State ◽  
Proton Transfer ◽  
Excited State Proton Transfer ◽  
Kinetics Of

scholarly journals Evaluation of the kinetics of oxidation and removal of organic matter in the self-purification of a mountain river

DYNA ◽  
2015 ◽  
Vol 82 (191) ◽  
pp. 183-193 ◽  
Author(s):  
Jorge Virgilio Rivera Gutiérrez
Keyword(s):  
Water Quality ◽  
Water System ◽  
The Self ◽  
Organic Load ◽  
Mountain River ◽  
Kinetics Of Oxidation ◽  
Kinetic Rates ◽  
High Concentrations ◽  
Kinetics Of

The study is based on the determination of the kinetic rates and assessment of self-purification of the Frio River, due to the uptake of organic load. The kinetic rates were calculated by applying differential and logarithmic methods on concentrations of water quality determinants present in each of the (7) reach of the river. The water system easily recovers the amount of oxygen, k<sub>d</sub>= 0.4, k<sub>a</sub> 3.2 d<sup>-1</sup>, only receives 27.7 Ton. d<sup>-1</sup>, the organic load, making high concentrations of carbon, ammonium and remain sediment. The length Influence of discharges, LIV- BOD yielded a mean per tranche of 10 km, compared to 3 km each way, means that the river can´t self- purification that need more length of travel. The study illustrates the modeling of the determinants of quality, developed by the QUAL2K, using the calculated rates.

scholarly journals Comparing hydrogen absorption kinetics of the samples of intermetallic compound and metal hydride compact on its basis

2021 ◽  
Vol 2057 (1) ◽  
pp. 012043
Author(s):  
I A Romanov ◽  
V I Borzenko ◽  
A N Kazakov
Keyword(s):  
Intermetallic Compound ◽  
Metal Hydride ◽  
Hydrogen Absorption ◽  
Reaction Rate ◽  
Nickel Foam ◽  
High Confidence ◽  
Compact Sample ◽  
Kinetics Of ◽  
Rate Controlling Step ◽  
Absorption Of Hydrogen

Abstract This work is devoted to an experimental study and comparison of the kinetics of hydrogen absorption by an intermetallic compound LaNi4.4Al0.3Fe0.3 in form of pure intermetallic compound free backfill and a compact based on it obtained by cold pressing with a spiral matrix of nickel-foam. To calculate the kinetic parameters of the hydrogen absorption reaction, the initial rates method is used. The PCT absorption isotherms are measured at temperatures of 313, 333, and 353 K. The experimental data are described with quite high confidence by the chosen model, which assumes that the reaction rate controlling step is the dissociative absorption of hydrogen on the surface of the a-phase. The rate of hydrogen absorption increases with increasing pressure drop and temperature. It is shown that the rate of hydrogen absorption by the sample of pure IMC is significantly less dependent on temperature compared to the compact sample. In addition, the reaction rate at temperatures of 313 and 333 K is higher for the free backfill sample, and at 353 K it is higher for the metal hydride compact. The values of the absorption constant and the activation energy of the hydrogen absorption reaction are determined for both samples.

Kinetics of Proton-transfer Reactions

Nature ◽  
1967 ◽  
Vol 213 (5071) ◽  
pp. 65-66 ◽  
Author(s):  
G. C. BARKER ◽  
D. C. SAMMON
Keyword(s):  
Proton Transfer ◽  
Transfer Reactions ◽  
Proton Transfer Reactions ◽  
Kinetics Of

Kinetics of proton-transfer reactions of p-nitrophenol in N-methylformamide

1983 ◽  
Vol 87 (14) ◽  
pp. 2584-2592 ◽  
Author(s):  
T. Oncescu ◽  
A. M. Oancea ◽  
L. De Maeyer
Keyword(s):  
Proton Transfer ◽  
Transfer Reactions ◽  
Proton Transfer Reactions ◽  
Kinetics Of

Kinetics of proton-transfer reactions of amino acids and simple polypeptides

1968 ◽  
Vol 90 (25) ◽  
pp. 6909-6913 ◽  
Author(s):  
Kenneth R. Applegate ◽  
Leon J. Slutsky ◽  
Richard C. Parker
Keyword(s):  
Amino Acids ◽  
Proton Transfer ◽  
Transfer Reactions ◽  
Proton Transfer Reactions ◽  
Kinetics Of
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