scholarly journals A Mechanistic Investigation of the Suzuki Polycondensation Reaction Using MS/MS Methods

2021 ◽  
Author(s):  
Michelle Ting ◽  
Lars Yunker ◽  
Ian Chagunda ◽  
Katherine Hatlelid ◽  
Meghan Vieweg ◽  
...  
Keyword(s):  
Active Catalyst ◽  
Multiple Reaction Monitoring ◽  
Catalytic Reactions ◽  
Decomposition Products ◽  
Polymerization Catalysis ◽  
Suzuki Polycondensation ◽  
Mechanistic Investigation ◽  
Reaction Proceeds ◽  
Modern Mass ◽  
Reaction Initiation

<p>Understanding catalytic reactions is inherently difficult because not only is the catalyst the least abundant component in the mixture, but it also takes many different forms as the reaction proceeds. Precatalyst is converted into active catalyst, short-lived intermediates, resting states, and decomposition products. Polymerization catalysis is harder yet to study, because as the polymer grows the identities of these species change with every turnover as monomers are added to the chain. Modern mass spectrometric methods have proved to be up to the challenge, with multiple reaction monitoring (MRM) in conjunction with pressurized sample infusion (PSI) used to continuously probe all stages of the Suzuki polycondensation (SPC) reaction. Initiation, propagation, and termination steps were tracked in real time, and the outstanding sensitivity and low signal-to-noise of the approach has real promise with respect to the depth with which this reaction and others like it can be studied.</p>

scholarly journals A Mechanistic Investigation of the Suzuki Polycondensation Reaction Using MS/MS Methods

2021 ◽  
Author(s):  
Michelle Ting ◽  
Lars Yunker ◽  
Ian Chagunda ◽  
Katherine Hatlelid ◽  
Meghan Vieweg ◽  
...  
Keyword(s):  
Active Catalyst ◽  
Multiple Reaction Monitoring ◽  
Catalytic Reactions ◽  
Decomposition Products ◽  
Polymerization Catalysis ◽  
Suzuki Polycondensation ◽  
Mechanistic Investigation ◽  
Reaction Proceeds ◽  
Modern Mass ◽  
Reaction Initiation

<p>Understanding catalytic reactions is inherently difficult because not only is the catalyst the least abundant component in the mixture, but it also takes many different forms as the reaction proceeds. Precatalyst is converted into active catalyst, short-lived intermediates, resting states, and decomposition products. Polymerization catalysis is harder yet to study, because as the polymer grows the identities of these species change with every turnover as monomers are added to the chain. Modern mass spectrometric methods have proved to be up to the challenge, with multiple reaction monitoring (MRM) in conjunction with pressurized sample infusion (PSI) used to continuously probe all stages of the Suzuki polycondensation (SPC) reaction. Initiation, propagation, and termination steps were tracked in real time, and the outstanding sensitivity and low signal-to-noise of the approach has real promise with respect to the depth with which this reaction and others like it can be studied.</p>

A mechanistic investigation of the Suzuki polycondensation reaction using MS/MS methods

2021 ◽  
Author(s):  
Michelle Yan Chi Ting ◽  
Lars Yunker ◽  
Ian C. Chagunda ◽  
Katherine Hatlelid ◽  
Meghan Vieweg ◽  
...  
Keyword(s):  
Catalytic Reactions ◽  
Polycondensation Reaction ◽  
Suzuki Polycondensation ◽  
Mechanistic Investigation ◽  
Reaction Proceeds

Understanding catalytic reactions is inherently difficult because not only is the catalyst the least abundant component in the mixture, but it also takes many different forms as the reaction proceeds....

A programmable soft chemo-mechanical actuator exploiting a catalyzed photochemical water-oxidation reaction

Soft Matter ◽  
2017 ◽  
Vol 13 (40) ◽  
pp. 7312-7317 ◽  
Author(s):  
P. Yuan ◽  
J. M. McCracken ◽  
D. E. Gross ◽  
P. V. Braun ◽  
J. S. Moore ◽  
...  
Keyword(s):  
Water Oxidation ◽  
Oxidation Reaction ◽  
Active Catalyst ◽  
Ph Gradients ◽  
Mechanistic Investigation ◽  
Interfacial Boundary ◽  
Mechanical Transformation ◽  
Covalently Linked

A mechanistic investigation is described for an actuatable bilayer polymeric device in which a covalently-linked photo-active catalyst drives systemic pH gradients, effecting reversible and cyclic mechanical transformation across the interfacial boundary.

scholarly journals Modeling and experimental study of polyurethane foaming and gelling reactions

2018 ◽  
Author(s):  
◽  
Luay Jaf
Keyword(s):  
Experimental Data ◽  
Foam Height ◽  
Research Process ◽  
Catalytic Reactions ◽  
Polymerization Process ◽  
Gel Point ◽  
Reaction Proceeds ◽  
Polyurethane Foaming ◽  
Kinetics Of ◽  
Insight Into

Numerous reactions take place within a polyurethane polymerization process. Homogeneous and catalytic reactions occur at the same time and intermediate compounds are formed. As the reaction proceeds, long chains of polymer are formed which drastically affect the kinetics of the reaction. Temperature and viscosity profiles of the reacting mixture are two strong indicators of the extent of reaction and the way the reactions are carried out. Therefore, simulating polyurethane gel and foam systems helps interpret temperature and viscosity profiles and gain insight into the kinetics of the system. Using MATLAB program, a model was introduced which simultaneously solves over 80 ordinary differential equations and provide temperature and viscosity profiles as well as concentration profiles, degrees of polymerization, gel point and foam height for individual formulations. Experimental data were used to validate the code showing the model is fundamentally correct. Simulation results showed good fits to the experimental data providing reaction kinetics of the system. The model was modified to simulate reaction systems with minimal change in kinetic parameters. Finally, the simulation studies of this research provide fundamental insights into mechanism of homogenous and catalytic reactions. This research process places high demands on identifying and testing highly-impacting fundamental mechanism during polymerization that have not previously been identified.

Influence of the Catalyst Preparation on Properties of Chromium-Magnesium Catalysts for Freon 125 Synthesis

2015 ◽  
Vol 670 ◽  
pp. 152-155
Author(s):  
Aleksandr Zirka ◽  
Ludmila Simonova ◽  
Natalia Kosova ◽  
Irina Kurzina ◽  
Sergey Reshetnikov
Keyword(s):  
Experimental Data ◽  
Gas Phase ◽  
Pore Diameter ◽  
Active Catalyst ◽  
Total Pore Volume ◽  
Catalyst Preparation ◽  
Catalytic Reactions ◽  
Bet Surface Area ◽  
Kinetics Of ◽  
Preparation Techniques

The effect of the chromium-magnesium precursor preparation techniques on physicochemical properties (BET surface area, total pore volume, mean pore diameter) and catalysts activity in the gas-phase hydrofluorination of perchloroethylene to pentafluoroethane (Freon 125) was studied. Kinetics of the catalytic reactions was studied for the most active catalyst. Based on the experimental data, the pathway of perchloroethylene fluorination with HF was suggested.

scholarly journals Fluorination of arylboronic esters enabled by bismuth redox catalysis

Science ◽  
2020 ◽  
Vol 367 (6475) ◽  
pp. 313-317 ◽  
Author(s):  
Oriol Planas ◽  
Feng Wang ◽  
Markus Leutzsch ◽  
Josep Cornella
Keyword(s):  
Transition Metals ◽  
Active Catalyst ◽  
Reductive Elimination ◽  
Redox Cycle ◽  
Redox Catalysis ◽  
Acidic Properties ◽  
Bond Forming ◽  
Mechanistic Investigation ◽  
Boronic Esters

Bismuth catalysis has traditionally relied on the Lewis acidic properties of the element in a fixed oxidation state. In this paper, we report a series of bismuth complexes that can undergo oxidative addition, reductive elimination, and transmetallation in a manner akin to transition metals. Rational ligand optimization featuring a sulfoximine moiety produced an active catalyst for the fluorination of aryl boronic esters through a bismuth (III)/bismuth (V) redox cycle. Crystallographic characterization of the different bismuth species involved, together with a mechanistic investigation of the carbon-fluorine bond-forming event, identified the crucial features that were combined to implement the full catalytic cycle.

scholarly journals Simultaneous Quantification of Propylthiouracil and Its N-β-d Glucuronide by HPLC-MS/MS: Application to a Metabolic Study

2021 ◽  
Vol 14 (11) ◽  
pp. 1194
Author(s):  
Min Li ◽  
Qingfeng He ◽  
Li Yao ◽  
Xiaofeng Wang ◽  
Zhijia Tang ◽  
...  
Keyword(s):  
Pediatric Population ◽  
Multiple Reaction Monitoring ◽  
Negative Ion ◽  
Metabolic Study ◽  
Simultaneous Quantification ◽  
Mechanistic Investigation ◽  
Age Dependent ◽  
Carry Over ◽  
Negative Ion Mode

Propylthiouracil (PTU) is commonly prescribed for the management of hyperthyroidism and thyrotoxicosis. Although the exact mechanism of action is not fully understood, PTU is associated with hepatoxicity in pediatric population. Glucuronidation mediated by uridine 5′-diphospho-glucuronosyltransferases (UGTs), which possess age-dependent expression, has been proposed as an important metabolic pathway of PTU. To further examine the metabolism of PTU, a reliable HPLC-MS/MS method for the simultaneous quantification of PTU and its N-β-D glucuronide (PTU-GLU) was developed and validated. The chromatographic separation was achieved on a ZORBAX Extend-C18 column (2.1 × 50 mm, 1.8 μm) through gradient delivery of a mixture of formic acid, methanol and acetonitrile. The electrospray ionization (ESI) was operated in its negative ion mode while PTU and PTU-GLU were detected by multiple reaction monitoring (MRM). This analytical method displayed excellent linearity, sensitivity, accuracy, precision, recovery and stability while its matrix effect and carry-over were insignificant. Subsequently, the in vitro metabolism of PTU was assessed and UGT1A9 was identified as an important UGT isoform responsible for the glucuronidation of PTU. The information obtained from this study will facilitate future mechanistic investigation on the hepatoxicity of PTU and may optimize its clinical application.

Photo-Induced Chromiumcarbonyl Catalyzed Hydrosilylation of Conjugated Dienes with Triethylsilane: The Solvent Effect

2003 ◽  
Vol 58 (7) ◽  
pp. 644-648 ◽  
Author(s):  
Ceyhan Kayran ◽  
Saim Özkar ◽  
Vagif M. Akhmedov
Keyword(s):  
Catalytic Activity ◽  
Solvent Effect ◽  
Active Catalyst ◽  
Conjugated Dienes ◽  
Catalytic Activities ◽  
Reaction Proceeds ◽  
The Stability ◽  
Reactivity Order ◽  
Sole Product ◽  
Hexane Solution

Photocatalytic hydrosilylation of conjugated dienes (1,3-butadiene, 2-methyl-1,3-butadiene, 2,3- dimethyl-1,3-butadiene, trans-1,3-pentadiene) with triethylsilane was studied by using Cr(CO)5L (L = CO, P(CH3)3, P(OCH3)3, P(C6H5)3, P(C6H11)3, NC5H5) in two very different solvents, toluene and tetrahydrofuran, for comparison with the results found in n-hexane. In toluene, the photocatalytic hydrosilylation yields the same products as those in n-hexane, with the exception of trans- 1,3-pentadiene which gives cis-1-triethylsilyl-2-pentene as the sole product. However, each of the precursor complexes shows different catalytic activities in toluene and n-hexane. The hydrosilylation of 1,3-butadiene in toluene is, in general, significantly faster than that in n-hexane. By using Cr(CO)6, Cr(CO)5[P(CH3)3] or Cr(CO)5[P(OCH3)3] in toluene, the conversion of triethylsilane increases almost linearly as the reaction proceeds, indicating the stability of the active catalyst throughout the reaction, similar to that in n-hexane. While no hydrosilylation of 1,3-butadiene could be achieved with Cr(CO)5[P(C6H5)3] or Cr(CO)5(NC5H5) in n-hexane, the same precursor complexes appear to be active in toluene, though the conversion occurs at much lower rate compared to that obtained using Cr(CO)5[P(CH3)3] or Cr(CO)5[P(OCH3)3]. The precursor complex Cr(CO)5[P(C6H11)3] shows catalytic activity neither in toluene nor in n-hexane. No photocatalytic hydrosilylation of 1,3-butadiene with triethylsilane was observed in tetrahydrofuran by using any of the precursor complexes. The relative reactivity of conjugated dienes in the hydrosilylation was investigated by using triethylsilane in the presence of Cr(CO)5[P(OCH3)3] as catalyst in toluene, and the same reactivity order was obtained as in n-hexane solution: 1,3-butadiene > 3-methyl-1,3-butadiene > 2,3-dimethyl-1,3-butadiene > trans-1,3-pentadiene. For all of the dienes, one obtains higher conversion to hydrosilylated product in toluene than in n-hexane.

scholarly journals Coupling photocatalytic water oxidation with organic reduction: strategy for using water to reduce organic molecules

2021 ◽  
Author(s):  
Xinzhe Tian ◽  
Yinggang Guo ◽  
Wenbo Liu ◽  
Yi Zheng ◽  
Yun-Lai Ren ◽  
...  
Keyword(s):  
Water Splitting ◽  
Water Oxidation ◽  
Organic Molecules ◽  
Reductive Coupling ◽  
Aryl Bromides ◽  
Mechanistic Investigation ◽  
Reaction Proceeds ◽  
Novel Method ◽  
High Yields ◽  
First Time

Abstract The utilization of readily available and non-toxic water by photocatalytic water splitting is highly attractive in green chemistry. Herein we report that light-induced oxidative half-reaction of water splitting is effectively coupled with reduction of organic compounds, which opens up, for the first time, an avenue to use water as an electron donor to enable reductive transformations of organic substances. The used photocatalyst (Pd/g-C3N4*) was synthetized by a novel method where Pd/g-C3N4 was irradiated by light in the presence of Na2CO3 and H2O. The present strategy allowed a series of aryl bromides to undergo the reductive coupling to provide biaryl products in low to high yields. Preliminary mechanistic investigation suggests that the reaction proceeds through the single electron transfer from Pd to aryl bromides. This work will guide chemists to use water as a reducing agent to develop green procedures for various organic reactions.

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