Organometallic ring vs. chain formation beyond kinetic control: steering their equilibrium in two-dimensional confinement

2018 ◽  
Vol 54 (70) ◽  
pp. 9741-9744 ◽  
Author(s):  
Claudio K. Krug ◽  
Qitang Fan ◽  
Florian Fillsack ◽  
Johannes Glowatzki ◽  
Nicole Trebel ◽  
...  
Keyword(s):  
Kinetic Control ◽  
Two Dimensional ◽  
Thermodynamic Control ◽  
Chain Formation

Two-dimensional confinement enables thermodynamic control over the competition between macrocycle and chain formation.

Experimental and Theoretical Investigation of the Reaction of Secondary Amines with Maleic Anhydride

2017 ◽  
Vol 70 (12) ◽  
pp. 1247 ◽  
Author(s):  
Manjinder Kour ◽  
Raakhi Gupta ◽  
Raj K. Bansal
Keyword(s):  
Maleic Anhydride ◽  
Carbonyl Group ◽  
Carbonyl Compounds ◽  
Secondary Amines ◽  
Kinetic Control ◽  
Thermodynamic Control ◽  
Carbonyl Carbon ◽  
Fukui Functions ◽  
Unsaturated Carbonyl Compound ◽  
Condensed Fukui Functions

The reaction of secondary amines, namely 1-methylpiperazine, pyrrolidine, morpholine, 2-methylpiperidine, and diethylamine, with maleic anhydride has been investigated experimentally and theoretically at the DFT level. Under kinetic control, i.e. at −78°C or −15°C, amines add across the C=O functionality exclusively and the initially formed addition products isomerize to the corresponding N-substituted maleimic acid derivatives. In contrast to the acyclic α,β-unsaturated carbonyl compounds, amine does not add across the C=C functionality in maleic anhydride even under thermodynamic control. This behaviour of maleic anhydride can be rationalized on the basis of the local condensed Fukui functions, which reveal that the carbonyl carbon atoms in maleic anhydride are much harder than in an acyclic α,β-unsaturated carbonyl compound, such as acrolein. This prompts the amines to attack the carbonyl group in maleic anhydride exclusively.

Dynamic stress chain formation in a two-dimensional particle bed

2002 ◽  
Vol 42 (3) ◽  
pp. 329-337 ◽  
Author(s):  
Keith M. Roessig ◽  
Joseph C. Foster ◽  
Scott G. Bardenhagen
Keyword(s):  
Dynamic Stress ◽  
Two Dimensional ◽  
Chain Formation ◽  
Particle Bed ◽  
Stress Chain

Helicity control in the synthesis of helicenes and related compounds

2006 ◽  
Vol 78 (2) ◽  
pp. 495-499 ◽  
Author(s):  
Ivo Starý ◽  
Irena G. Stará ◽  
Zuzana Alexandrová ◽  
Petr Sehnal ◽  
Filip Teplý ◽  
...  
Keyword(s):  
Asymmetric Synthesis ◽  
Kinetic Control ◽  
Thermodynamic Control ◽  
Further Development ◽  
Related Compounds

Asymmetric synthesis of helicenes and their congeners has been demonstrated to rely either on enantioselective Ni0/PR3*-catalyzed [2+2+2] cycloisomerization of triynes or on diastereoselective CoI-catalyzed [2+2+2] cycloisomerization of chiral triynes. The former approach providing tetrahydrohelicenes in a nonracemic form requires further development as moderate enantioselectivities (up to 54 % ee) have so far been achieved under kinetic control. The latter approach affording helicene-like structures in a diastereomerically enriched form allows for reaching good to excellent diastereoselectivities (up to 100:0) under thermodynamic control.

scholarly journals QUANTUM CHEMITRY STUDY ON STRUCTURES, ACTIVITIES AND REACTIONS OF ONIUM-BORONIUM DICATIONS

2010 ◽  
Vol 13 (2) ◽  
pp. 45-52
Author(s):  
Thanh Tho Bui ◽  
Tran Thi Bao Vo
Keyword(s):  
Activation Energy ◽  
Intrinsic Reaction Coordinate ◽  
Kinetic Control ◽  
Ab Initio Methods ◽  
Thermodynamic Control ◽  
Imaginary Frequency ◽  
Theoretical Investigations ◽  
Transition Structures ◽  
Frequency Calculation ◽  
Energy Activation

This paper provides information about theoretical investigations of structures of onium-boronium dications X+BH3+, X+BH5+; (X= NH3, PH3, H2O, H2S) and some reactions of them in thermodynamic control and kinetic control. Two kinds of reactions studied are complexation of onium-boronium dications X+BH3+ with H2 leading to X+BH5+ and deprotonation of X+BH5+ to give X+BH4. The similar studies with boronium ion analog BH4+ and BH6+ is carried out and results obtained pointed out that the eletrophility of onium-boronium dications is more stronger than that of boronium ion: onium-boronium dications X+BH3+, X+BH5+ are superelectrophiles. The structures of onium-boronium dications and boronium ions are optimized by using ab initio methods at the MP2/6-311+G** level of Gaussian 03W, revision B.04 and represented with Gaussview 3.0. Frequency calculation is performed to assure the obtained structures corresponding to minimun energies and have no any imaginary frequency. The transition structures are calculated and verified due to Intrinsic Reaction Coordinate Calculations. The properties of structures, as MP2 energy, Gibbs free energy, activation energy are also examined.

scholarly journals Metal control of selectivity in acetate-assisted C–H bond activation: an experimental and computational study of heterocyclic, vinylic and phenylic C(sp2)–H bonds at Ir and Rh

2014 ◽  
Vol 5 (6) ◽  
pp. 2340-2346 ◽  
Author(s):  
Kevin J. T. Carr ◽  
David L. Davies ◽  
Stuart A. Macgregor ◽  
Kuldip Singh ◽  
Barbara Villa-Marcos
Keyword(s):  
Bond Activation ◽  
Computational Study ◽  
Metal Catalyst ◽  
Kinetic Control ◽  
Dft Studies ◽  
Thermodynamic Control

Experimental and DFT studies show the selectivity of C–H bond activation at [MCl2Cp*]2 (M = Ir, Rh) species can be controlled by the choice of metal catalyst, reflecting kinetic control at M = Ir and thermodynamic control at M = Rh.

Variable stoichiometry with thermodynamic control in ADM1

2006 ◽  
Vol 54 (4) ◽  
pp. 101-110 ◽  
Author(s):  
J. Rodríguez ◽  
J.M. Lema ◽  
M.C.M. van Loosdrecht ◽  
R. Kleerebezem
Keyword(s):  
Anaerobic Digestion ◽  
Kinetic Control ◽  
Thermodynamic Control ◽  
Mixed Culture Fermentation ◽  
Effluent Quality ◽  
Fermentation Model ◽  
Carbohydrate Fermentation ◽  
Typical Behaviour ◽  
System Robustness ◽  
Variable Stoichiometry

The effect of a variable stoichiometry of the carbohydrate fermentation process in the IWA Anaerobic Digestion Model No.1 (ADM1) is investigated. Most existing anaerobic digestion models including ADM1 consider a fixed-stoichiometry for their conversion processes. The ADM1 model was first transformed into an only mol based model to remove some errors derived from the mixed COD-mol based standard model and to allow for implementation of the variable stoichiometry. Consequently, the values of the butyrate and acetate catabolic yields of carbohydrate fermentation are made dependent on the hydrogen concentration and the reactor pH according to the predictions of a recently developed mixed culture fermentation model based on thermodynamic considerations. The simulation results obtained showed no significantly different responses in terms of effluent quality and system robustness between the standard and the variable stoichiometry ADM1 under overload conditions, and for both single- and two-step anaerobic digestion configurations. This behaviour is explained by the non-limiting acetogenic activity that compensated for the changes in the acidogenic products, typical behaviour for serial processes close to equilibrium. Based on the results obtained, thermodynamic rather than kinetic control for these conversions is suggested. Depending on the objectives to be met, lumping of carbohydrate fermenters and oxidative acetogens into a single biomass group with a variable stoichiometry is proposed for further consideration.

scholarly journals Overcoming Selectivity Issues in Reversible Catalysis – A Transfer Hydrocyanation Exhibiting High Kinetic Control

2020 ◽  
Author(s):  
Benjamin N. Bhawal ◽  
Julia C. Reisenbauer ◽  
Christian Ehinger ◽  
Bill Morandi
Keyword(s):  
Lewis Acid ◽  
Reductive Elimination ◽  
Catalytic Reactions ◽  
Transfer Reactions ◽  
Kinetic Control ◽  
Selective Transfer ◽  
Thermodynamic Control ◽  
New Horizons ◽  
Reversible Transfer ◽  
Kinetic Selectivity

<p><i>Typically, reversible catalytic reactions operate under thermodynamic control and thus establishing a selective catalytic system poses a considerable challenge. In this manuscript, we report a reversible yet kinetically selective transfer hydrocyanation protocol. Selectivity is achieved by exploiting the lower barrier for C–CN oxidative addition and reductive elimination at benzylic positions in the absence of co-catalytic Lewis acid. The design of a novel type of HCN donor was crucial to realizing this practical, branched-selective, HCN-free transfer hydrocyanation. The synthetically useful resolution of a mixture of branched and linear nitrile isomers was also demonstrated to underline the value of reversible and selective transfer reactions. In a broader context, this work demonstrates that high kinetic selectivity can be achieved in reversible transfer reactions, thus opening new horizons for their synthetic applications.</i></p>

scholarly journals Thermodynamic Control of Two-Dimensional Molecular Ionic Nanostructures on Metal Surfaces

ACS Nano ◽  
2016 ◽  
Vol 10 (8) ◽  
pp. 7821-7829 ◽  
Author(s):  
Seokmin Jeon ◽  
Peter W. Doak ◽  
Bobby G. Sumpter ◽  
Panchapakesan Ganesh ◽  
Petro Maksymovych
Keyword(s):  
Metal Surfaces ◽  
Two Dimensional ◽  
Thermodynamic Control

Rate constants for the addition of the enolate ion of acetone to quinolinium and acridinium cations

1990 ◽  
Vol 68 (10) ◽  
pp. 1762-1768 ◽  
Author(s):  
John W. Bunting ◽  
Cynthia Fu ◽  
James W. Tam
Keyword(s):  
Ionic Strength ◽  
Aqueous Solutions ◽  
Rate Constants ◽  
Nucleophilic Addition ◽  
Ph Dependence ◽  
Adduct Formation ◽  
Kinetic Control ◽  
Thermodynamic Control ◽  
Hydroxide Ion ◽  
Kinetically Controlled

The reaction of acetone with four heteroaromatic cations (10-methylacridinium (1), 3-aminocarbonyl-1-methylquinolinium (2a), 3-cyano-1-methylquinolinium (2b), and 3-bromo-1-methylquinolinium (2c)) has been investigated in basic aqueous solutions (pH 9–12, ionic strength 0.1, 25 °C). For each of 2a and 2b, the kinetically controlled product is a 35:65 mixture of the C-2 and C-4 enolate ion adducts; the C-2 adduct subsequently isomerizes to give the C-4 adduct as the only observable species under thermodynamic control. For 2c, the C-2 enolate adduct appears to be favoured both kinetically and thermodynamically. Under kinetic control, the pH-dependence of adduct formation from each cation is consistent with rate-determining attack of the enolate ion upon the heterocyclic cation. Comparisons of regiochemical control of acetone enolate ion attack with hydroxide ion attack upon these same cations indicate that acetone enolate ion shows a more pronounced preference for C-4 attack over C-2 attack than does hydroxide ion. The thermodynamically controlled regiochemistry is similar for each of these two nucleophiles. Keywords: nucleophilic addition, regioselectivity, kinetic control, thermodynamic control, quinolinium cations.

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