scholarly journals The kinetics and mechanism of photooxygenation of 4′-diethylamino-3-hydroxyflavone

2016 ◽  
Vol 15 (2) ◽  
pp. 219-227 ◽  
Author(s):  
Zoltán Szakács ◽  
Márton Bojtár ◽  
László Drahos ◽  
Dóra Hessz ◽  
Mihály Kállay ◽  
...  
Keyword(s):  
Salicylic Acid ◽  
Quantum Yield ◽  
Acid Derivative ◽  
Rate Constant ◽  
Reaction Path ◽  
Kinetics And Mechanism

4′-Diethylamino-3-hydroxyflavone is oxidized into a salicylic acid derivative under photolysis. The rate constant and the quantum yield of the photooxidation have been determined and – on the basis of PES calculations – the reaction path has been analyzed.

scholarly journals Synthesis, kinetics and mechanism of nucleophilic substitution in octahedral (cat)2Sn(py)2

2005 ◽  
Vol 70 (12) ◽  
pp. 1389-1393 ◽  
Author(s):  
K.S. Siddiqi ◽  
Shahab Nami
Keyword(s):  
Nucleophilic Substitution ◽  
Rate Constant ◽  
Substitution Reaction ◽  
Molar Conductance ◽  
Chloride Ions ◽  
Kinetics And Mechanism ◽  
Nucleophilic Substitution Reaction ◽  
Nucleophilic Reagents

Dicatecholatodipyridinetin(IV) in nitrobenzene showed an increase in molar conductance with time, suggesting solvation of the complex. In the presence of nucleophilic reagents, such as SOCl2, C6H5COCl and CH3COCl, the conductance increased sharply owing to the substitution of pyridine by chloride ions. The data for the rate constant of solvation (k s) and for nucleophilic substitution (k 1 and k 2) have been calculated and it was found that the solvation is a slower process compared to the substitution by chloride ions, i.e., k1, k 2 > k s. The nucleophilic substitution reaction follows the SN1 mechanism.

scholarly journals Mechanistic Investigations of an α-Aminoarylation Photoredox Reaction

2021 ◽  
Author(s):  
Bernard Stevenson ◽  
Ethan Spielvogel ◽  
Emily Loiaconi ◽  
Victor M. Wambua ◽  
Roman Nakhamiyayev ◽  
...  
Keyword(s):  
Quantum Yield ◽  
Absorption Spectroscopy ◽  
Rate Constant ◽  
Kinetic Modeling ◽  
Rate Constants ◽  
Transient Absorption ◽  
Coupling Reaction ◽  
Time Dependent ◽  
Transient Absorption Spectroscopy ◽  
Mechanistic Investigations

We present time-dependent percent and quantum yield measurements of a photoredox-catalyzed coupling reaction between 1,4-dicyanobenzene and N-phenylpyrrolidine. We also use transient absorption spectroscopy to examine the kinetics within the reaction and use kinetic modeling to extract rate constants and predict how changes in rate constant will impact the quantum yield.

Serum Concentrations of Salicylic Acid following Topically Applied Salicylate Derivatives

1996 ◽  
Vol 30 (9) ◽  
pp. 935-940 ◽  
Author(s):  
Pina Morra ◽  
William R Bartle ◽  
Scott E Walker ◽  
S Nicole Lee ◽  
Susan K Bowles ◽  
...  
Keyword(s):  
Salicylic Acid ◽  
Rate Constant ◽  
Maximum Concentration ◽  
Methyl Salicylate ◽  
Absorption Rate ◽  
The Other ◽  
Pharmacokinetic Parameters ◽  
Absorption Rate Constant ◽  
Serum Concentrations ◽  
Women Volunteers

OBJECTIVE: To compare the rate and extent of systemic salicylate absorption following single and multiple applications of two topically applied analgesics, one containing methyl salicylate and the other containing trolamine salicylate. DESIGN: Two-period, two-treatment, randomized, crossover, multiple-dose study in healthy men and women volunteers. PARTICIPANTS: Six men and six women volunteers, 21–14 years of age. INTERVENTIONS: Subjects applied 5 g of an ointment containing 12.5% methyl salicylate twice daily for 4 days (8 doses) or a cream containing trolamine 10% twice daily for two doses, to a 10-cm2 area on the thigh. Treatment order and leg (right or left) were assigned randomly. Subjects were crossed over to the alternate treatment on the other leg after a minimum washout period of 7 days. MAIN OUTCOME MEASURES: The total amount of salicylate recovered in the urine during two dosing intervals (24 hours) on each study day, relative to the applied dose, was used to calculate the bioavailability of each product. Mean standard pharmacokinetic parameters including area under the curve, maximum concentration (Cmax), time to maximum concentration, and minimum concentrations at steady-state were determined from serum concentrations. Serum concentrations were fit to three pharmacokinetic models and the suitability of each model was evaluated. Estimates of absorption rate constant, clearance, volume, and fraction absorbed on day 1 were estimated by using the best-fitting model. RESULTS: Salicylic acid could not be detected in serum after trolamine application. However, concentrations between 0.31 and 0.91 mg/L were detected within 1 hour of the first application of methyl salicylate and Cmax, between 2 and 6 mg/L were observed following the seventh application on day 4. Both the extent and rate of absorption changed after the first 24 hours. The absorption rate constant increased significantly from the first to the seventh dose (first dose absorption rate constant: 0.16 h−1; seventh dose: 0.28 h−1; p < 0.035). Urinary recovery of total salicylate (salicylic acid and principal metabolites of salicylic acid) during the first 24 hours of the methyl salicylate phase averaged 175.2 mg, exceeding the 6.9 mg (p < 0.05) recovered during the trolamine phase. The recovery of salicylate in the urine in the first 24 hours after application of methyl salicylate was significantly greater than the 1.4% recovered after application of trolamine (p < 0.05). Furthermore, the fraction of methyl salicylate recovered in the urine increased significantly from 15.5% on day 1 to approximately 22% on the second, third, and fourth days. CONCLUSIONS: A considerable amount of salicylic acid may be absorbed through the skin after topical application of methyl salicylate products and this may increase with multiple applications. Caution is warranted in patients for whom systemic salicylate may be hazardous or problematic.

Hypouricemic effect of MK 647, a new salicylic acid derivative, in normal human

Abstracts ◽  
1977 ◽  
pp. 258
Author(s):  
Albert Dresse ◽  
Paul Fischer ◽  
Marie-Anne Gérard ◽  
Léo Verhaest ◽  
Ken Tempero
Keyword(s):  
Salicylic Acid ◽  
Acid Derivative ◽  
Normal Human

Photochemical reaction kinetics and mechanism of bisphenol A with K2S2O8 in aqueous solution: a laser flash photolysis study

2021 ◽  
Vol 99 (1) ◽  
pp. 43-50
Author(s):  
Yongchao Zhu ◽  
Mengyu Zhu ◽  
Jingjing Xie ◽  
Yadong Hu ◽  
Ying Liu ◽  
...  
Keyword(s):  
Bisphenol A ◽  
Rate Constant ◽  
Photochemical Reaction ◽  
Flash Photolysis ◽  
Laser Flash Photolysis ◽  
Phenoxyl Radical ◽  
Laser Flash ◽  
Kinetics And Mechanism ◽  
Main Reaction ◽  
Specific Rate

The photochemical reaction kinetics and mechanism of bisphenol A (BPA) with potassium persulfate (K2S2O8) were investigated by using 266 nm laser flash photolysis and gas chromatography mass spectrum (GC-MS) technique. Sulfate radical (SO4•−), generated upon K2S2O8 photolysis, reacted with BPA with the overall rate constant of (1.61 ± 0.15) × 109 L mol−1 s−1, and two main reaction mechanisms were involved. One was addition channel to generate BPA–SO4•− adduct with a specific second-order rate constant of (1.09 ± 0.15) × 109 L mol−1 s−1. Molecular oxygen was involved in the decay of the BPA–SO4•− adduct with a rate constant of (1.28 ± 0.14) × 108 L mol−1 s−1. Another channel was the formation of BPA’s phenoxyl radical, likely derived from a deprotonation of the cation radical (BPA•+) generated from single electron transfer reactions. The specific rate constant of BPA’s phenoxyl radical formation was determined to be (6.16 ± 0.08) × 108 L mol−1 s−1. The overall rate constant was in line with the sum of aforementioned two specific rate constants for two main reaction channels. By comparing these rate constants, it was indicated that SO4•− addition channel accounted for ∼65% (1.09/1.61) to the overall reaction, and phenoxyl radical formation accounted for only ∼35% (0.62/1.61). The transformation products of BPA were identified by using GC-MS including 4-isopropylphenol, 4-isopropenylphenol, and 2,4-di-tert-butylphenol, and the reaction mechanism was proposed. These results may provide microscopic kinetics and mechanism information on BPA degradation using SO4•−-based advanced oxidation processes.

Sign in / Sign up

Export Citation Format

Share Document