Abiotic CC bond formation under environmental conditions: Kinetics of the aldol condensation of acetaldehyde in water catalyzed by carbonate ions (CO3 2− )

2010 ◽  
Vol 42 (11) ◽  
pp. 676-686 ◽  
Author(s):  
Barbara Nozière ◽  
Perrine Chabert
Keyword(s):  
Environmental Conditions ◽  
Aldol Condensation ◽  
Bond Formation ◽  
Carbonate Ions ◽  
Kinetics Of

Topography of the Free Energy Landscape on the Claisen-Schmidt Condensation: Solvent and Temperature Effect in the Rate-Controlling Step

2021 ◽  
Author(s):  
Nayara Dantas Coutinho ◽  
Hugo Gontijo Machado ◽  
Valter Henrique Carvalho-Silva ◽  
Wender A. Silva
Keyword(s):  
Free Energy ◽  
Temperature Effect ◽  
Strong Influence ◽  
Aldol Condensation ◽  
Energy Landscape ◽  
Bond Formation ◽  
Free Energy Landscape ◽  
Rate Controlling Step ◽  
Formation Step

Recent studies have assigned hydroxide elimination and C=C bond formation step in base-promoted aldol condensation the role of having a strong influence in the overall rate reaction, in contrast to...

scholarly journals Laboratory study on OH-initiated degradation kinetics of dehydroabietic acid

2015 ◽  
Vol 17 (16) ◽  
pp. 10953-10962 ◽  
Author(s):  
Chengyue Lai ◽  
Yongchun Liu ◽  
Jinzhu Ma ◽  
Qingxin Ma ◽  
Hong He
Keyword(s):  
Laboratory Study ◽  
Environmental Conditions ◽  
Degradation Kinetics ◽  
Dehydroabietic Acid ◽  
Oh Radicals ◽  
Kinetics Of

The degradation kinetics of dehydroabietic acid by OH radicals were investigated under various environmental conditions.

Liquid-phase aldol condensation of cyclohexanone on aluminium and iron oxides

1982 ◽  
Vol 47 (8) ◽  
pp. 2235-2245 ◽  
Author(s):  
Zdeněk Vít ◽  
Lubomír Nondek ◽  
Jaroslav Málek
Keyword(s):  
Iron Oxides ◽  
Aldol Condensation ◽  
Condensation Reaction ◽  
Complex Function ◽  
Acid Sites ◽  
Basic Site ◽  
Catalyst Poisoning ◽  
Iron Hydroxides ◽  
Transient Complex ◽  
Kinetics Of

The kinetics of the aldol condensation of cyclohexanone in decalin were investigated at 210 °C on catalysts prepared by drying and calcining the aluminium and iron hydroxides at 110-850 °C. The effect of catalyst poisoning by benzoic acid and pyridine on the course of the condensation reaction and aldol retroaldolisation was also examined. The kinetics of the cyclohexanone condensation can be described by means of Langmuir-Hinshelwood equations which are in agreement with a mechanism involving adsorption of cyclohexanone on a basic site to form a transient complex, reaction of this complex with a cyclohexanone molecule affording the aldol, the rate determining interaction of the aldol with free basic and acid sites yielding 2-(1-cyclohexen-1-yl)cyclohexanone and water and desorption of these products from the catalyst surface. The proposed kinetic model is supported by the results of catalyst poisoning. The activity of aluminium and iron oxides in the condensation of cyclohexanone is a complex function of their basicity and acidity depending strongly on the calcination temperature.

The effect of clam shell powder on kinetics of water absorption of jute epoxy composite

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Hemalata Jena ◽  
Abinash Panigrahi
Keyword(s):  
Water Absorption ◽  
Environmental Conditions ◽  
Epoxy Composite ◽  
Jute Fibre ◽  
Content Type ◽  
Clam Shell ◽  
New Class ◽  
Kinetics Of ◽  
Shell Powder ◽  
Marine Waste

Purpose Here, attempts have been made to explore the possible use of Marine waste as filler materials into the bio-fibre composites. Clam shell is a type of marine waste which belongs to the class of Bivalvia. It is mainly made of aragonite crystalline polymorphs. This paper aims to develop a new class of natural fibre composite in which jute fibre as reinforcement, epoxy as matrix and clam shell, as particulate microsphere filler. The study investigates the effects of different amounts of clam shell powder on the kinetics of water absorption of jute fibre-reinforced epoxy composite. Two different environmental conditions at room temperature, i.e. distilled water and seawater, are collected for this purpose. Moisture absorption reduces when clam shell is added to the jute-epoxy composite. The curve of water absorption of jute-epoxy composites with filler loading at both environmental conditions follows as Fickian behaviour. Design/methodology/approach Hand lay-up technique to fabricate the composite – Experimental observation Findings The incorporation of Clam shell filler in jute epoxy composite modified the water absorption property of the composite. Hence the present marine waste is an potential filler in jute fibre reinforced polymer composite. Originality/value The paper demonstrates a new class hybrid composite material which uses a marine waste as important phase in the bio-fibre-reinforced composite. It is a new work submitted for original research paper.

Kinetics of Coordinate Bond Formation. V. Kinetics of the Reaction P(CH3)3+BF3

1961 ◽  
Vol 34 (3) ◽  
pp. 715-717 ◽  
Author(s):  
G. B. Kistiakowsky ◽  
C. E. Klots
Keyword(s):  
Bond Formation ◽  
Coordinate Bond ◽  
Kinetics Of

Catalytic routes to fuels from C1 and oxygenate molecules

2017 ◽  
Vol 197 ◽  
pp. 9-39 ◽  
Author(s):  
Shuai Wang ◽  
Iker Agirrezabal-Telleria ◽  
Aditya Bhan ◽  
Dante Simonetti ◽  
Kazuhiro Takanabe ◽  
...  
Keyword(s):  
Transition State ◽  
Active Sites ◽  
Aldol Condensation ◽  
Bond Formation ◽  
Transition States ◽  
Solid Acids ◽  
State Theory ◽  
Side Reactions ◽  
Oh Radicals ◽  
Acid Base

This account illustrates concepts in chemical kinetics underpinned by the formalism of transition state theory using catalytic processes that enable the synthesis of molecules suitable as fuels from C1 and oxygenate reactants. Such feedstocks provide an essential bridge towards a carbon-free energy future, but their volatility and low energy density require the formation of new C–C bonds and the removal of oxygen. These transformations are described here through recent advances in our understanding of the mechanisms and site requirements in catalysis by surfaces, with emphasis on enabling concepts that tackle ubiquitous reactivity and selectivity challenges. The hurdles in forming the first C–C bond from C1 molecules are illustrated by the oxidative coupling of methane, in which surface O-atoms form OH radicals from O2 and H2O molecules. These gaseous OH species act as strong H-abstractors and activate C–H bonds with earlier transition states than oxide surfaces, thus rendering activation rates less sensitive to the weaker C–H bonds in larger alkane products than in CH4 reactants. Anhydrous carbonylation of dimethyl ether forms a single C–C bond on protons residing within inorganic voids that preferentially stabilize the kinetically-relevant transition state through van der Waals interactions that compensate for the weak CO nucleophile. Similar solvation effects, but by intrapore liquids instead of inorganic hosts, also become evident as alkenes condense within MCM-41 channels containing isolated Ni2+ active sites during dimerization reactions. Intrapore liquids preferentially stabilize transition states for C–C bond formation and product desorption, leading to unprecedented reactivity and site stability at sub-ambient temperatures and to 1-alkene dimer selectivities previously achieved only on organometallic systems with co-catalysts or activators. C1 homologation selectively forms C4 and C7 chains with a specific backbone (isobutane, triptane) on solid acids, because of methylative growth and hydride transfer rates that reflect the stability of their carbenium ion transition states and are unperturbed by side reactions at low temperatures. Aldol condensation of carbonyl compounds and ketonization of carboxylic acids form new C–C bonds concurrently with O-removal. These reactions involve analogous elementary steps and occur on acid–base site pairs on TiO2 and ZrO2 catalysts. Condensations are limited by α-H abstraction to form enolates via concerted interactions with predominantly unoccupied acid–base pairs. Ketonization is mediated instead by C–C bond formation between hydroxy-enolates and monodentate carboxylates on site pairs nearly saturated by carboxylates. Both reactions are rendered practical through bifunctional strategies, in which H2 and a Cu catalyst function scavenge unreactive intermediates, prevent sequential reactions and concomitant deactivation, and remove thermodynamic bottlenecks. Alkanal–alkene Prins condensations on solid acids occur concurrently with alkene dimerization and form molecules with new C–C bonds as skeletal isomers unattainable by other routes. Their respective transition states are of similar size, leading to selectivities that cannot sense the presence of a confining host. Prins condensation reactions benefit from weaker acid sites because their transition states are less charged than those for oligomerization and consequently less sensitive to conjugate anions that become less stable as acids weaken.

scholarly journals Carbonatation and Decarbonatation Kinetics in the La2O3-La2O2CO3System under CO2Gas Flows

2010 ◽  
Vol 2010 ◽  
pp. 1-6 ◽  
Author(s):  
Bahcine Bakiz ◽  
Frédéric Guinneton ◽  
Madjid Arab ◽  
Abdeljalil Benlhachemi ◽  
Sylvie Villain ◽  
...  
Keyword(s):  
Gas Flow ◽  
Electrical Impedance ◽  
Ionic Conduction ◽  
Ionic Mobility ◽  
Phase Changes ◽  
Electrical Impedance Spectroscopy ◽  
Electrical Measurements ◽  
Carbonate Ions ◽  
Ionic Mobilities ◽  
Kinetics Of

The carbonatation of La2O3oxide and the decarbonatation of lanthanum carbonate phase La2O2CO3are investigated using thermal and thermogravimetry analyses under CO2gas flow. The initial phase La2O3is first elaborated from pyrolysis of a LaOHCO3precursor. Then, thermal and thermogravimetry analyses are carried out under CO2flow, as temperature increases then decreases. The carbonatation kinetics of La2O3is determined at three fixed temperatures. Electrical impedance spectroscopy is performed to determine the electrical responses associated with ionic mobilities and phase changes, in the temperature range 25 to900∘C. The electrical conduction during heating underCO2gas flow should be linked to two regimes of ionic conduction of the carbonate ions. From these electrical measurements, the ionic mobility of carbonate ionsCO3  2−is found to be close to 0.003 ⋅10−4 cm2 s−1 V−1at750∘C for the monoclinic La2O2CO3phase.

Kinetics of arsenite oxidation by Sinorhizobium sp. M14 under changing environmental conditions

2017 ◽  
Vol 119 ◽  
pp. 476-485 ◽  
Author(s):  
Klaudia Debiec ◽  
Jan Krzysztoforski ◽  
Witold Uhrynowski ◽  
Aleksandra Sklodowska ◽  
Lukasz Drewniak
Keyword(s):  
Environmental Conditions ◽  
Arsenite Oxidation ◽  
Kinetics Of

Degradation kinetics of a potent antifouling agent, butenolide, under various environmental conditions

Chemosphere ◽  
2015 ◽  
Vol 119 ◽  
pp. 1075-1083 ◽  
Author(s):  
Lianguo Chen ◽  
Ying Xu ◽  
Wenxiong Wang ◽  
Pei-Yuan Qian
Keyword(s):  
Environmental Conditions ◽  
Degradation Kinetics ◽  
Antifouling Agent ◽  
Kinetics Of
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