scholarly journals Substrate-Solvent Crosstalk – Effects on Reaction Kinetics and Product Selectivity in Olefin Oxidation Catalysis

2021 ◽  
Author(s):  
Rita N. Sales ◽  
Sam K. Callear ◽  
Pedro D. Vaz ◽  
Carla D. Nunes
Keyword(s):  
Ring Opening ◽  
Reaction Rate ◽  
Styrene Oxide ◽  
Oxidation Catalysis ◽  
Product Selectivity ◽  
Oxidation Reactions ◽  
Olefin Oxidation ◽  
Reaction Systems ◽  
Ring Opening Reaction ◽  
Oxide Conversion

In this work we explored how solvents can affect olefin oxidation reactions catalyzed by MCM-bpy-Mo catalysts and whether their control can be made with those players. The results of this study evidenced that polar and apolar aprotic solvents modulated the reactions in different ways. Experimental data showed that acetonitrile (aprotic polar) could hinder largely the reaction rate whereas toluene (aprotic apolar) did not. In both cases product selectivity at isoconversion was not affected. Further insights were obtained by means of neutron diffraction experiments, which confirmed the kinetic data allowing to propose a model based on substrate-solvent crosstalk by means of hydrogen bonding. In addition, the model was also validated in the ring-opening reaction (overoxidation) of styrene oxide towards benzaldehyde, which progressed when toluene was the solvent (reaching 31% styrene oxide conversion) but was strongly hindered when acetonitrile was used instead (reaching only 7% conversion), due to the establishment of H-bonds in the latter. Although this model was confirmed and validated for olefin oxidation reactions, it can be envisaged that it may also be applied to other catalytic reaction systems where reaction control is critical, while widening its use.

scholarly journals Substrate–Solvent Crosstalk—Effects on Reaction Kinetics and Product Selectivity in Olefin Oxidation Catalysis

Chemistry ◽  
2021 ◽  
Vol 3 (3) ◽  
pp. 753-764
Author(s):  
Rita N. Sales ◽  
Samantha K. Callear ◽  
Pedro D. Vaz ◽  
Carla D. Nunes
Keyword(s):  
Ring Opening ◽  
Reaction Rate ◽  
Styrene Oxide ◽  
Oxidation Catalysis ◽  
Product Selectivity ◽  
Oxidation Reactions ◽  
Olefin Oxidation ◽  
Reaction Systems ◽  
Ring Opening Reaction ◽  
Oxide Conversion

In this work, we explored how solvents can affect olefin oxidation reactions catalyzed by MCM-bpy-Mo catalysts and whether their control can be made with those players. The results of this study demonstrated that polar and apolar aprotic solvents modulated the reactions in different ways. Experimental data showed that acetonitrile (aprotic polar) could largely hinder the reaction rate, whereas toluene (aprotic apolar) did not. In both cases, product selectivity at isoconversion was not affected. Further insights were obtained by means of neutron diffraction experiments, which confirmed the kinetic data and allowed for the proposal of a model based on substrate–solvent crosstalk by means of hydrogen bonding. In addition, the model was also validated in the ring-opening reaction (overoxidation) of styrene oxide to benzaldehyde, which progressed when toluene was the solvent (reaching 31% styrene oxide conversion) but was strongly hindered when acetonitrile was used instead (reaching only 7% conversion) due to the establishment of H-bonds in the latter. Although this model was confirmed and validated for olefin oxidation reactions, it can be envisaged that it may also be applied to other catalytic reaction systems where reaction control is critical, thereby widening its use.

Flyby reaction trajectories: Chemical dynamics under extrinsic force

Science ◽  
2021 ◽  
Vol 373 (6551) ◽  
pp. 208-212
Author(s):  
Yun Liu ◽  
Soren Holm ◽  
Jan Meisner ◽  
Yuan Jia ◽  
Qiong Wu ◽  
...  
Keyword(s):  
Ring Opening ◽  
Important Determinant ◽  
Chemical Reactivity ◽  
Mechanistic Model ◽  
Polymer Chains ◽  
Product Selectivity ◽  
Dynamic Effects ◽  
Modeling And Simulations ◽  
Ring Opening Reaction ◽  
Intramolecular Motions

Dynamic effects are an important determinant of chemical reactivity and selectivity, but the deliberate manipulation of atomic motions during a chemical transformation is not straightforward. Here, we demonstrate that extrinsic force exerted upon cyclobutanes by stretching pendant polymer chains influences product selectivity through force-imparted nonstatistical dynamic effects on the stepwise ring-opening reaction. The high product stereoselectivity is quantified by carbon-13 labeling and shown to depend on external force, reactant stereochemistry, and intermediate stability. Computational modeling and simulations show that, besides altering energy barriers, the mechanical force activates reactive intramolecular motions nonstatistically, setting up “flyby trajectories” that advance directly to product without isomerization excursions. A mechanistic model incorporating nonstatistical dynamic effects accounts for isomer-dependent mechanochemical stereoselectivity.

Selective ring-opening reaction of styrene oxide with lithium azide in the presence of cyclodextrins in aqueous media

1992 ◽  
Vol 3 (2) ◽  
pp. 247-250 ◽  
Author(s):  
Alain Guy ◽  
Joël Doussot ◽  
Robert Garreau ◽  
Annie Godefroy-Falguieres
Keyword(s):  
Ring Opening ◽  
Styrene Oxide ◽  
Aqueous Media ◽  
Ring Opening Reaction ◽  
Selective Ring Opening

scholarly journals Two Possible Side Reaction Pathways during Furanic Etherification

Catalysts ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 383 ◽  
Author(s):  
Wenting Fang ◽  
Hualei Hu ◽  
Zhongsen Ma ◽  
Lei Wang ◽  
Yajie Zhang
Keyword(s):  
Ring Opening ◽  
Reaction Rate ◽  
Side Reaction ◽  
Side Reactions ◽  
Catalytic Systems ◽  
Theoretical Yield ◽  
Ring Opening Reaction ◽  
Hierarchical Porous ◽  
Deactivation Process ◽  
By Products

The revealing mechanism of side reactions is crucial for obtaining theoretical yield in industrialization when 2,5-bis(methoxymethyl)furan (BMMF) yield is above 95%. By-products catalyzed by the conventional ZSM-5 (C-ZSM-5) and hierarchical porous ZSM-5 (HP-ZSM-5) catalytic systems were different, and some key by-products were identified. Thus, possible pathways were proposed, which helps to further improve BMMF selectivity. Additionally, HP-ZSM-5 exhibited quicker reaction rate, higher BMMF yield and selectivity, and slower deactivation process. The relatively weak acidity of HP-ZSM-5 suppresses the ring-opening reaction and subsequent side reactions, and introduction of mesopores improves mass transport and slightly increases hydration of 2,5-bis(hydroxymethyl)furan (BHMF).

Oxidase Catalysis via an Aerobically Generated Dess-Martin Periodinane Analogue

2018 ◽  
Author(s):  
Asim Maity ◽  
Sung-Min Hyun ◽  
Alan Wortman ◽  
David Powers
Keyword(s):  
Chemical Synthesis ◽  
Aerobic Oxidation ◽  
Substrate Oxidation ◽  
Oxidation Catalysis ◽  
Hypervalent Iodine ◽  
Oxidation Reactions ◽  
Broad Array ◽  
Oxidation Chemistry ◽  
Reactive Oxidants

<p>Hypervalent iodine(V) reagents, such as Dess-Martin periodinane (DMP) and 2-iodoxybenzoic acid (IBX), are broadly useful oxidants in chemical synthesis. Development of strategies to access these reagents from O2 would immediately enable use of O2 as a terminal oxidant in a broad array of substrate oxidation reactions. Recently we disclosed the aerobic synthesis of I(III) reagents by intercepting reactive oxidants generated during aldehyde autoxidation. Here, we couple aerobic oxidation of iodobenzenes with disproportionation of the initially generated I(III) compounds to generate I(V) reagents. The aerobically generated I(V) reagents exhibit substrate oxidation chemistry analogous to that of DMP. Further, the developed aerobic generation of I(V) has enabled the first application of I(V) intermediates in aerobic oxidation catalysis.</p>

On the Conrotatory Ring Opening of 3-Carbomethoxycyclobutene Vis-À-Vis 3-Carbomethoxy-1,2-Benzocyclobutene and the Predominant Inward Opening of 3-Dimethylaminocarbonyl-1,2-Benzocyclobutene

2018 ◽  
Author(s):  
Veejendra Yadav ◽  
Dasari L V K Prasad ◽  
Arpita Yadav ◽  
Maddali L N Rao
Keyword(s):  
Transition State ◽  
Ring Opening ◽  
Electron Process ◽  
Ring Opening Reaction ◽  
Stable Species ◽  
Electron Event

<p>The torquoselectivity of conrotatory ring opening of 3-carbomethoxycyclobutene is controlled by p<sub>C1C2</sub>→s*<sub>C3C4</sub> and s<sub>C3C4</sub>→p*<sub>CO</sub> interactions in the transition state in a 4-electron process as opposed to only s<sub>C3C4</sub>→p*<sub>CO</sub> interaction in an apparently 8-electron event in 3-carbomethoxy-1,2-benzocyclobutene. The ring opening of 3-carbomethoxy-1,2-benzocyclobutene is sufficiently endothermic. We therefore argue that the reverse ring closing reaction is faster than the forward ring opening reaction and, thus, it establishes an equilibrium between the two and subsequently allows formation of the more stable species <i>via</i> outward ring opening reaction. Application of this argument to 3-dimethylaminocarbonyl-1,2-benzocyclobutene explains the predominantly observed inward opening.</p>

Tuning the Activities of Cu2O Nanostructures via the Oxide-Metal Interaction

2019 ◽  
Author(s):  
Wugen Huang ◽  
qingfei liu ◽  
Zhiwen Zhou ◽  
Yangsheng Li ◽  
Yong Wang ◽  
...  
Keyword(s):  
Co Oxidation ◽  
Oxidation Catalysis ◽  
Atomic Scale ◽  
Scanning Tunneling ◽  
Oxidation Reactions ◽  
Tunneling Microscopy ◽  
Temperature Oxidation ◽  
Metal Interaction ◽  
Tremendous Importance ◽  
Oxygen Atoms

Despite tremendous importance in catalysis, the design and improvement of the oxide- metal interface has been hampered by the limited understanding on the nature of interfacial sites, as well as the oxide-metal interaction (OMI). Through the construction of well-defined Cu<sub>2</sub>O-Pt, Cu<sub>2</sub>O-Ag, Cu<sub>2</sub>O-Au interfaces, we found that Cu<sub>2</sub>O Nanostructures (NSs) on Pt exhibit much lower thermal stability than on Ag and Au, although they show the same surface and edge structures, as identified by element-specific scanning tunneling microscopy (ES-STM) images. The activities of the Cu<sub>2</sub>O-Pt and Cu<sub>2</sub>O-Au interfaces for CO oxidation were further compared at the atomic scale and showed in general that the interface with Cu<sub>2</sub>O NSs could annihilate the CO-poisoning problem suffered by Pt group metals and enhance the interaction with O<sub>2</sub>, which is a limiting step for CO oxidation catalysis on group IB metals. While both interfaces could react with CO at room temperature, the OMI was found to determine the reactivity of supported Cu<sub>2</sub>O NSs by 1) tuning the activity of interfacial oxygen atoms and 2) stabilizing oxygen vacancies or vice versa, the dissociated oxygen atoms at the interface. Our study provides new insight for OMI and for the development of Cu-based catalysts for low temperature oxidation reactions.

Tuning the Activities of Cu2O Nanostructures via the Oxide-Metal Interaction

2019 ◽  
Author(s):  
Wugen Huang ◽  
Yangsheng Li ◽  
Yong Wang ◽  
Yunchuan Tu ◽  
Dehui Deng ◽  
...  
Keyword(s):  
Co Oxidation ◽  
Oxidation Catalysis ◽  
Atomic Scale ◽  
Scanning Tunneling ◽  
Oxidation Reactions ◽  
Tunneling Microscopy ◽  
Temperature Oxidation ◽  
Metal Interaction ◽  
Tremendous Importance ◽  
Oxygen Atoms

Despite tremendous importance in catalysis, the design and improvement of the oxide- metal interface has been hampered by the limited understanding on the nature of interfacial sites, as well as the oxide-metal interaction (OMI). Through the construction of well-defined Cu<sub>2</sub>O-Pt, Cu<sub>2</sub>O-Ag, Cu<sub>2</sub>O-Au interfaces, we found that Cu<sub>2</sub>O Nanostructures (NSs) on Pt exhibit much lower thermal stability than on Ag and Au, although they show the same surface and edge structures, as identified by element-specific scanning tunneling microscopy (ES-STM) images. The activities of the Cu<sub>2</sub>O-Pt and Cu<sub>2</sub>O-Au interfaces for CO oxidation were further compared at the atomic scale and showed in general that the interface with Cu<sub>2</sub>O NSs could annihilate the CO-poisoning problem suffered by Pt group metals and enhance the interaction with O<sub>2</sub>, which is a limiting step for CO oxidation catalysis on group IB metals. While both interfaces could react with CO at room temperature, the OMI was found to determine the reactivity of supported Cu<sub>2</sub>O NSs by 1) tuning the activity of interfacial oxygen atoms and 2) stabilizing oxygen vacancies or vice versa, the dissociated oxygen atoms at the interface. Our study provides new insight for OMI and for the development of Cu-based catalysts for low temperature oxidation reactions.

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