scholarly journals Identifying reaction pathways in phase space via asymptotic trajectories

2020 ◽  
Vol 22 (18) ◽  
pp. 10087-10105
Author(s):  
Yutaka Nagahata ◽  
F. Borondo ◽  
R. M. Benito ◽  
Rigoberto Hernandez
Keyword(s):  
Phase Space ◽  
Reaction Pathway ◽  
Reaction Pathways

The asymptotic trajectories indicate the edge of the reaction pathway.

Reaction Pathways to 2-Aminothiophenes and Thiophene-3-carbonitriles

2009 ◽  
Vol 62 (5) ◽  
pp. 402 ◽  
Author(s):  
Luigi Aurelio ◽  
Bernard L. Flynn ◽  
Peter J. Scammells
Keyword(s):  
Comparative Studies ◽  
Reaction Pathway ◽  
Reaction Pathways ◽  
Synthesis And Characterization ◽  
The Past ◽  
Adenosine A1 ◽  
Unexpected Reaction ◽  
Potential Applications ◽  
A1 Receptor

Over the past two decades 2-amino-3-benzoylthiophenes have been found to act as allosteric enhancers of the adenosine A1 receptor (A1AR). As such, compounds of this type have potential applications in the therapy of a variety of disorders by enhancing A1AR activation. Initial studies in this field identified various 2-amino-3-benzoylthiophenes as potential leads and of these PD 81723 1a has become the benchmark for comparative studies due to its favourable ratio of allosteric enhancement to antagonism. Surprisingly the synthesis and characterization of PD 81723 1a has not been previously reported. Herein we report the synthesis and characterization of this important A1AR allosteric enhancer. As part of this study we also found an unexpected reaction pathway to 2-phenylthiophene-3-carbonitriles.

1999 R.U. Lemieux Award Lecture Adventures with azo-, azoxy-, and hydrazoarenes: from the Wallach to the benzidine rearrangement. Molecular electronics

2000 ◽  
Vol 78 (10) ◽  
pp. 1251-1271 ◽  
Author(s):  
Erwin Buncel
Keyword(s):  
Molecular Electronics ◽  
Rate Constant ◽  
Reaction Pathway ◽  
Solvent Polarity ◽  
Molecular Switch ◽  
Reaction Pathways ◽  
Optical Data ◽  
Constant Ratio ◽  
Rate Constant Ratio ◽  
Acid Catalyzed

The author's studies with aromatic azo-, azoxy-, and hydrazo-dye molecules, comprising kinetic and equilibrium investigations, as well as synthesis of novel molecules having photogenic properties, are described under the following highlights: A. Wallach rearrangement and cognate studies with azoxyarenes — (1) Elucidation of the mechanism of the Wallach rearrangement of azoxybenzene through the kinetic observation of a two-proton process which, together with a pKa study, was interpreted on the basis of formation of a deoxygenated, dicationic, symmetrical species as a key, short-lived reaction intermediate. (2) The proposal of a general acid-catalyzed pathway in concentrated sulfuric acid (catalysis by H2SO4 and H3SO+4. (3) Elucidation of the consecutive sulfonations of reaction products of azoxybenzene in the 100% H2SO4 region, and the diprotonation equilibria for p-hydroxyazobenzene, thus shedding light on past reaction pathway and product studies. (4) The observation of a novel reaction pathway for 2,4,6,2',4',6'-hexamethy lazoxybenzene. (5) The observation of a dichotomy of reaction pathways for α- and β-2-phenylazoxynaphthalenes: reaction via the dicationic intermediate and via quinoid intermediate species; comprising two isomeric compounds reacting by different pathways to give the same product. (6) Identification and structure proof of α- and β-isomers observed for the first time in the peracid oxidation of phenylazopyridine. (7) Observation of a rate constant ratio of 22 000 in the rearrangement of these α- and β-isomers, and the proposal of differential barriers for transition states leading to a tricationic intermediate. B. Benzidine rearrangement and cognate studies — (8) Observation of the acid-catalyzed hydroxylation of phenylazopyridine to p-hydroxyphenylazopyridine and the proposal of an SNAr mechanism with formation of an intermediate hydrazo species in the reaction. (9) First study of benzidine type rearrangement-disproportionation of phenylhydrazopyridine in acid media. (10) Proposal of a A [Formula: see text] B [Formula: see text] C [Formula: see text] D type reaction profile for the consecutive hydroxylation[Formula: see text]disproportionation processes of phenylazopyridine in aq H2SO4. (11) Proposal of 10-π and 14π-electron electrocyclic processes in the benzidine type rearrangement-disproportionation of phenylhydrazopyridine. (12) Identification and structural elucidation of a dimer formed from phenylazopyridine as a minor product and proposal of a reaction mechanism. C. Facile acid-catalyzed demethylation via SNAr/A-SE2 mechanisms and studies of tautomerism — (13) Observation of an abnormally facile acid-catalyzed cleavage (demethylation) of 4-methoxyphenylazopyridine via an SNAr mechanism. (14) Observation of two reaction pathways, SNAr and A-SE2, for the consecutive demethylations of 3,4-dimethoxyphenylazopyridine, with rate constant ratio of 7 000:1 favoring the SNAr process. (15) Quantitation of the tautomeric and protonation equilibria of 4-hydroxyphenylazopyridine, produced in (13). D. A new solvent polarity scale, molecular switches, and molecular electronics — (16) Establishment of a π*azo solvent polarity scale based on solvatochromism of a series of azomerocyanine molecules ("Buncel's dye"). (17) Some glimpses are presented of current forays into molecular electronics, as emanating from the above studies: (a) spiropyran (SP) <—> merocyanine (MC) thermo- and photochromic "molecular switch" systems; (b) synthesis and characterization of azo-functionalized star-burst dendrimers with photoswitchable properties and potential applications in optical data storage systems, holographic gratings, and drug delivery systems as host molecules.Key words: Wallach rearrangement, benzidine disproportionation, azoarenes, azoxyarenes, dendrimers, hydrazoarenes, dendrimers, solvatochromism, photochromism, thermochromism, spiropyran-merocyanine molecular switch.

Adsorption and reaction pathways of a chiral probe molecule, S-glycidol on a Pd(111) surface

2015 ◽  
Vol 5 (2) ◽  
pp. 738-742 ◽  
Author(s):  
Mausumi Mahapatra ◽  
Wilfred T. Tysoe
Keyword(s):  
Infrared Spectroscopy ◽  
Reaction Pathway ◽  
Temperature Programmed Desorption ◽  
Reaction Pathways ◽  
Probe Molecule ◽  
Reflection Absorption Infrared Spectroscopy ◽  
Temperature Programmed

The chemistry of S-glycidol is studied on a Pd(111) surface using temperature-programmed desorption and reflection–absorption infrared spectroscopy to explore its suitability as a chiral probe molecule and to follow its reaction pathway.

scholarly journals Green synthesis via electrolysis in microemulsions

2001 ◽  
Vol 73 (12) ◽  
pp. 1895-1905 ◽  
Author(s):  
James F. Rusling
Keyword(s):  
Turnover Rate ◽  
Recent Progress ◽  
Reaction Pathway ◽  
Reaction Rates ◽  
Synthetic Methods ◽  
Reaction Pathways ◽  
Lower Toxicity ◽  
Reduction Potentials ◽  
Covalently Linked ◽  
High Yields

Electrolysis in microemulsions is a promising approach for environmentally friendly chemical synthetic methods of the future. Employing microemulsions instead of organic solvents for electrosynthesis has the advantages of lower toxicity and cost, high dissolving power for reactants and mediators of unlike solubility, enhancement of reaction rates by controlling the reduction potentials of mediators, possible reaction pathway control, and recycling of microemulsion components. This paper reviews recent progress in using microemulsions for direct and mediated electrosynthesis, including formation of carbon­carbon bonds. Rates of mediated reactions can be controlled by manipulating microemulsion composition. Examples are presented, in which reaction pathways of direct and mediated electrolyses can be controlled with microemulsions to give desired products in high yields. Such control has been demonstrated with dissolved and surface-bound mediators. For a covalently linked scaffold of poly(l-lysine) and cobalt corrin vitamin B12 hexacarboxylate attached to graphite, catalytic turnover rate for reduction of 1,2-dibromocylcohexane was optimized by optimizing microemulsion composition.

Switching a nitrilase from Syechocystis sp. PCC6803 to a nitrile hydratase by rationally regulating reaction pathways

2017 ◽  
Vol 7 (5) ◽  
pp. 1122-1128 ◽  
Author(s):  
Shuiqin Jiang ◽  
Lujia Zhang ◽  
Zhiqiang Yao ◽  
Bei Gao ◽  
Hualei Wang ◽  
...  
Keyword(s):  
Nitrile Hydratase ◽  
Reaction Pathway ◽  
Reaction Pathways

Based on this mechanism, a nitrilase was engineered to shift the reaction pathway from formation of acid to formation of amide.

Thermodynamic Analysis of Aqueous Phase Reforming of Sorbitol

2020 ◽  
Vol 17 (2) ◽  
pp. 1004-1008 ◽  
Author(s):  
Najwa Afaf Nadzru ◽  
Ain Syuhada ◽  
Mohammad Tazli Azizan ◽  
Mariam Ameen
Keyword(s):  
Simulation Model ◽  
Thermodynamic Analysis ◽  
Energy Minimization ◽  
Reaction Pathway ◽  
Reaction Pathways ◽  
Main Reaction ◽  
Aqueous Phase Reforming ◽  
Minimization Principle ◽  
Different Temperatures ◽  
Gibbs Free Energy Minimization

The objectives of this study were to investigate the most thermodynamically favoured reaction pathway during APR of sorbitol. The thermodynamic analysis of APR of sorbitol was studied using ASPEN Plus V8.0 by applying Gibbs free energy minimization principle, operating at different temperatures (300–800 K), pressure (10–30 bar) and sorbitol concentration (1%, 3%, 5%, 10%, 15% and 20%). The simulation model was validated by comparing the results with the existing work conducted by Serentis and Tsiakaras. The results obtained show that the mol fraction and trend of H2, CO2 and CH4 for both cases are almost similar to the existing work. Therefore the simulation model was validated. Five main reaction pathways of APR of sorbitol were identified and intermediates of each reaction pathway were defined according to their stages and their composition was analyzed. The result obtained show that the decarbonylation reaction (pathway 2) is the most thermodynamically favoured pathway with a total dry basis percentage of 21%.

scholarly journals The Effect of Polymer Addition on Base Catalysed Glycerol Oxidation Using Gold and Gold–Palladium Bimetallic Catalysts

2019 ◽  
Vol 63 (3-4) ◽  
pp. 394-402 ◽  
Author(s):  
Laura Abis ◽  
Nikolaos Dimitritatos ◽  
Meenakshisundaram Sankar ◽  
Simon J. Freakley ◽  
Graham J. Hutchings
Keyword(s):  
Bimetallic Catalysts ◽  
Reaction Rate ◽  
Catalyst Surface ◽  
Reaction Pathway ◽  
Reaction Pathways ◽  
Palladium Nanoparticle ◽  
Catalytic Systems ◽  
Nanoparticle Catalysts ◽  
Catalytic Upgrading ◽  
Polymer Addition

Abstract The oxidation of glycerol represents both a viable route to catalytic upgrading of biomass and has become a model reaction for catalytic polyol oxidation. Gold and gold–palladium nanoparticle catalysts prepared by colloidal methods involving polymer additives have been extensively studied. However, the effect of residual polymer at the catalyst surface on reaction pathways has not been decoupled from particle size effects. We show that when using catalysts prepared without polymer stabilisers the addition of either polyvinyl alcohol or polyvinylpyrrolidone to the reaction changes the reaction rate and results in a change in reaction selectivity. We conclude that the polymer additive has a significant effect on the reaction pathway and that these systems should be considered as a metal surface–polymer interface catalytic systems and properties should not be rationalised solely based on nanoparticle size. Graphic Abstract

A Competitive Model Reaction for the Ribosomal Peptide Bond Formation Catalyzed by Peptidyl Transferase

2014 ◽  
Vol 496-500 ◽  
pp. 17-20
Author(s):  
Lin Cheng ◽  
Nian Hong ◽  
Xiang Qun Xu ◽  
Jie Yang ◽  
You Quan Zhong
Keyword(s):  
Reaction Pathway ◽  
Bond Formation ◽  
Peptide Bond ◽  
Model Reaction ◽  
Reaction Pathways ◽  
Peptide Bond Formation ◽  
Peptidyl Transferase ◽  
Reaction Field ◽  
Self Consistent ◽  
Competitive Model

In this work, a series of theoretical methods were employed to investigate the reaction mechanisms of ribosomal peptide bond formation catalyzed by peptidyl transferase. For the studies described in this paper, reaction pathways and free energy barriers for the model reaction of the peptide bond synthesis were studied by performing Ab initio calculation. Two self-consistent reaction field (SCRF) methods were used to calculate of the whole reaction pathway. These results show that the present theoretical reaction mechanism is a potential and competitive one for the reaction modeling of the ribosomal peptide synthesis.

scholarly journals A graph-based network for predicting chemical reaction pathways in solid-state materials synthesis

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Matthew J. McDermott ◽  
Shyam S. Dwaraknath ◽  
Kristin A. Persson
Keyword(s):  
Solid State ◽  
Chemical Reaction ◽  
Reaction Pathway ◽  
Reaction Network ◽  
Functional Materials ◽  
Reaction Pathways ◽  
Materials Synthesis ◽  
Pathway Prediction ◽  
Solid State Materials ◽  
Cost Paths

AbstractAccelerated inorganic synthesis remains a significant challenge in the search for novel, functional materials. Many of the principles which enable “synthesis by design” in synthetic organic chemistry do not exist in solid-state chemistry, despite the availability of extensive computed/experimental thermochemistry data. In this work, we present a chemical reaction network model for solid-state synthesis constructed from available thermochemistry data and devise a computationally tractable approach for suggesting likely reaction pathways via the application of pathfinding algorithms and linear combination of lowest-cost paths in the network. We demonstrate initial success of the network in predicting complex reaction pathways comparable to those reported in the literature for YMnO3, Y2Mn2O7, Fe2SiS4, and YBa2Cu3O6.5. The reaction network presents opportunities for enabling reaction pathway prediction, rapid iteration between experimental/theoretical results, and ultimately, control of the synthesis of solid-state materials.

scholarly journals Emission Rate Estimation of Fuel Oil in A Combustion System Using Empirical Method

2019 ◽  
Vol 4 (12) ◽  
pp. 6-8
Author(s):  
N. Harry-Ngei ◽  
I. Ubong ◽  
E. Ojong
Keyword(s):  
Emission Rate ◽  
Reaction Pathway ◽  
Empirical Method ◽  
Fuel Oil ◽  
Reaction Pathways ◽  
Emission Rates ◽  
Combustion System ◽  
Complete Combustion ◽  
Incomplete Combustion ◽  
Oil Flow

This work highlighted the prediction of the emission rates of the products of combustion using a fuel oil of specific gravity of 0.9. The two reaction pathways of complete combustion and incomplete combustion were used differently to ascertain the emission rates. Ultimate analysis were conducted on the fuel oil to show the percentage composition of elements using ASTM 3178 method for carbon and hydrogen, Kjedahl method for nitrogen, ASTM D1552 for sulphur and the differences used to compute that of oxygen. The estimated percentages of the various elements were the stoichiometrically used to compute the emissions rates at standard conditions. The basis of the computation was a fuel oil flow rate of 10Tonnes/h and the following emission rates were predicted for the complete combustion reaction pathway: 31,246Kg/h for CO2, 65Kg/h for H2O, 158Kg/h for NO2 and 20Kg/h for SO2 while 9,940Kg/h for CO2, 15,623Kg/h for CO, 11,700Kg/h for H2O, 11Kg/h for H2S and 158Kg/h for NO2 were predicted for the incomplete combustion pathway. The study noted that this predictive path should be taken where effective devices or logistics are not in place to measure emissions from combustion systems.

Sign in / Sign up

Export Citation Format

Share Document