DFT study on the side reactions of Aldol condensation on MgO in the production of 1,3-butadiene from ethanol

2021 ◽  
Vol 543 ◽  
pp. 148771
Author(s):  
Yingzhe Yu ◽  
Hai Chen ◽  
Yantao Hu ◽  
Minhua Zhang
Keyword(s):  
Aldol Condensation ◽  
Dft Study ◽  
Side Reactions

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 Reaction Mechanism of 2-Amido-2-Aminoacetic Acid-Formation from Amides and 2-Iminoacetic Acid: A DFT-study and Wavefunction Analysis

2021 ◽  
Author(s):  
Georg Dazinger
Keyword(s):  
Reaction Mechanism ◽  
Dft Study ◽  
Acid Formation ◽  
Side Reactions ◽  
Aminoacetic Acid ◽  
Diamino Acid ◽  
Wavefunction Analysis ◽  
Acid Esters

<p> Based on a study of Wei Zeng et. al.[7], where the synthesis of <i>gem</i>-diamino acid esters from 2-iminoacetic acid esters and amides, with various N- and C-substituents, respectively, is reported, a modeled reaction, where the latter substituents were replaced by H, was simulated by means of DFT. A reasonable reaction mechanism was found for the formation of 2-amido-2-aminoacetic acid from formamide and 2-iminoacetic acid. Moreover, possible side reactions were simulated and discussed.</p>

A DFT study of aldol condensation reaction in the process of ethanol to 1,3-butadiene on MgO/SiO2 surface

2021 ◽  
Author(s):  
Weiwei Zhang ◽  
Dan Fan ◽  
Yingzhe Yu
Keyword(s):  
Ethanol Production ◽  
Aldol Condensation ◽  
Condensation Reaction ◽  
Catalyst System ◽  
Dft Study ◽  
Sio2 Surface

MgO/SiO2, a significant catalyst system for ethanol production of 1,3-butadiene. The aldol condensation reaction is a key step in the reaction of ethanol to 1,3- butadiene. In this work, density...

scholarly journals Mechanism of Side Reactions in Alkane CH Bond Functionalization by Diazo Compounds Catalyzed by Ag and Cu Homoscorpionate Complexes-A DFT Study

ChemCatChem ◽  
2011 ◽  
Vol 3 (10) ◽  
pp. 1646-1652 ◽  
Author(s):  
Ataualpa A. C. Braga ◽  
Ana Caballero ◽  
Juan Urbano ◽  
M. Mar Diaz-Requejo ◽  
Pedro J. Pérez ◽  
...  
Keyword(s):  
Dft Study ◽  
Diazo Compounds ◽  
Side Reactions ◽  
Bond Functionalization

scholarly journals Reaction Mechanism of 2-Amido-2-Aminoacetic Acid-Formation from Amides and 2-Iminoacetic Acid: A DFT-study and Wavefunction Analysis

2020 ◽  
Author(s):  
Georg Dazinger
Keyword(s):  
Reaction Mechanism ◽  
Dft Study ◽  
Acid Formation ◽  
Side Reactions ◽  
Aminoacetic Acid ◽  
Diamino Acid ◽  
Wavefunction Analysis ◽  
Acid Esters

<p> Based on a study of Wei Zeng et. al.[7], where the synthesis of <i>gem</i>-diamino acid esters from 2-iminoacetic acid esters and amides, with various N- and C-substituents, respectively, is reported, a modeled reaction, where the latter substituents were replaced by H, was simulated by means of DFT. A reasonable reaction mechanism was found for the formation of 2-amido-2-aminoacetic acid from formamide and 2-iminoacetic acid. Moreover, possible side reactions were simulated and discussed.</p>

A DFT study on the aldol condensation reaction on MgO in the process of ethanol to 1,3-butadiene: understanding the structure–activity relationship

2017 ◽  
Vol 19 (37) ◽  
pp. 25671-25682 ◽  
Author(s):  
Dan Fan ◽  
Xiuqin Dong ◽  
Yingzhe Yu ◽  
Minhua Zhang
Keyword(s):  
Aldol Condensation ◽  
Condensation Reaction ◽  
Structure Activity Relationship ◽  
Dft Study ◽  
Activity Relationship ◽  
Structure Activity

The mechanism of aldol condensation on MgO surfaces with different structures was investigated to illustrate the structure–activity relationship.

scholarly journals Reaction Mechanism of 2-Amido-2-Aminoacetic Acid-Formation from Amides and 2-Iminoacetic Acid: A DFT-study and Wavefunction Analysis

2020 ◽  
Author(s):  
Georg Dazinger
Keyword(s):  
Reaction Mechanism ◽  
Dft Study ◽  
Acid Formation ◽  
Side Reactions ◽  
Aminoacetic Acid ◽  
Diamino Acid ◽  
Wavefunction Analysis ◽  
Acid Esters

<p> Based on a study of Wei Zeng et. al.[7], where the synthesis of <i>gem</i>-diamino acid esters from 2-iminoacetic acid esters and amides, with various N- and C-substituents, respectively, is reported, a modeled reaction, where the latter substituents were replaced by H, was simulated by means of DFT. A reasonable reaction mechanism was found for the formation of 2-amido-2-aminoacetic acid from formamide and 2-iminoacetic acid. Moreover, possible side reactions were simulated and discussed.</p>

Aldehyde gold clusters for molecular labeling

1995 ◽  
Vol 53 ◽  
pp. 858-859
Author(s):  
James F. Hainfeld ◽  
Frederic R. Furuya
Keyword(s):  
Covalent Bond ◽  
Aldehyde Group ◽  
Gold Clusters ◽  
Side Reactions ◽  
Amino Groups ◽  
Sodium Cyanoborohydride ◽  
Schiff’S Base ◽  
Protein Molecules ◽  
Hydroxysuccinimide Esters ◽  
Primary Amino

Glutaraldehyde is a useful tissue and molecular fixing reagents. The aldehyde moiety reacts mainly with primary amino groups to form a Schiff's base, which is reversible but reasonably stable at pH 7; a stable covalent bond may be formed by reduction with, e.g., sodium cyanoborohydride (Fig. 1). The bifunctional glutaraldehyde, (CHO-(CH2)3-CHO), successfully stabilizes protein molecules due to generally plentiful amines on their surface; bovine serum albumin has 60; 59 lysines + 1 α-amino. With some enzymes, catalytic activity after fixing is preserved; with respect to antigens, glutaraldehyde treatment can compromise their recognition by antibodies in some cases. Complicating the chemistry somewhat are the reported side reactions, where glutaraldehyde reacts with other amino acid side chains, cysteine, histidine, and tyrosine. It has also been reported that glutaraldehyde can polymerize in aqueous solution. Newer crosslinkers have been found that are more specific for the amino group, such as the N-hydroxysuccinimide esters, and are commonly preferred for forming conjugates. However, most of these linkers hydrolyze in solution, so that the activity is lost over several hours, whereas the aldehyde group is stable in solution, and may have an advantage of overall efficiency.

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