scholarly journals Asymmetric Cyanation of Activated Olefins with Ethyl Cyanoformate Catalyzed by Ti(IV)-Catalyst: A Theoretical Study

Catalysts ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1079
Author(s):  
Zhishan Su ◽  
Changwei Hu ◽  
Nasir Shahzad ◽  
Chan Kyung Kim
Keyword(s):  
Transition State ◽  
Self Assembly ◽  
Theoretical Study ◽  
Activation Barrier ◽  
Cinchona Alkaloid ◽  
Activation Process ◽  
Construction Step ◽  
Dual Activation ◽  
Membered Transition State ◽  
Step Mechanism

The reaction mechanism and origin of asymmetric induction for conjugate addition of cyanide to the C=C bond of olefin were investigated at the B3LYP-D3(BJ)/6-31+G**//B3LYP-D3(BJ)/6-31G**(SMD, toluene) theoretical level. The release of HCN from the reaction of ethyl cyanoformate (CNCOOEt) and isopropanol (HOiPr) was catalyzed by cinchona alkaloid catalyst. The cyanation reaction of olefin proceeded through a two-step mechanism, in which the C-C bond construction was followed by H-transfer to generate a cyanide adduct. For non-catalytic reaction, the activation barrier for the rate-determining C-H bond construction step was 34.2 kcal mol−1, via a four-membered transition state. The self-assembly Ti(IV)-catalyst from tetraisopropyl titanate, (R)-3,3′-disubstituted biphenol, and cinchonidine accelerated the addition of cyanide to the C=C double bond by a dual activation process, in which titanium cation acted as a Lewis acid to activate the olefin and HNC was orientated by hydrogen bonding. The steric repulsion between the 9-phenanthryl at the 3,3′-position in the biphenol ligand and the Ph group in olefin raised the Pauli energy (ΔE≠Pauli) of reacting fragments at the re-face attack transition state, leading to the predominant R-product.

Halide ion-driven self-assembly of Zn(ii) compounds derived from an asymmetrical hydrazone building block: a combined experimental and theoretical study

2016 ◽  
Vol 40 (12) ◽  
pp. 10116-10126 ◽  
Author(s):  
Ghodrat Mahmoudi ◽  
Farhad Akbari Afkhami ◽  
Himanshu Sekhar Jena ◽  
Parisa Nematollahi ◽  
Mehdi D. Esrafili ◽  
...  
Keyword(s):  
Self Assembly ◽  
Building Block ◽  
Theoretical Study ◽  
Counter Ion ◽  
Non Covalent Interactions ◽  
Covalent Interactions

Self-assembly of Zn(ii) compounds is influenced by a counter ion and non-covalent interactions.

A Theoretical Study of the Lubricating Abilities of 2D Layered Hydrogen Bonded Systems

2018 ◽  
Author(s):  
Chloe Graham
Keyword(s):  
Self Assembly ◽  
Molecular Mechanisms ◽  
Theoretical Study ◽  
Financial Impact ◽  
Layered Systems ◽  
Friction Forces ◽  
Slip Mechanism ◽  
Hands On ◽  
Hydrogen Bonded Systems ◽  
Short Time

It has been estimated that 100 million terajoules of energy is used every year to combat friction. For perspective, this corresponds to one fifth of the world’s total energy expenditure. This significant amount leaves plenty of room for improvement. To reduce the environmental and financial impact of friction, lubricants are usually placed in mechanical systems and act as a barrier between moving parts. Lubricants come in many forms but they all have low energy slip mechanisms and resistance to conformational change under pressure. Chemicals with these properties can be predicted through some educated guesswork and computational simulations. Its advantageous to look at novel lubricants computationally because each small reaction can be analyzed, whereas in the lab it may be difficult to see the molecular mechanisms taking place in such short time spans. Additionally, computation is more environmentally friendly than hands-on testing because no chemicals are used. My research studies compounds found in nature and assesses their potential for use as lubricants. The focus of my studies has been on layered systems of melamine molecules that self-assemble into two-dimensional structures through hydrogen bonding. The layered nature of this system is similar to that of graphite – an effective layered lubricant; however, the reversibility of self-assembly may allow the layered structure to reform when disrupted during sliding to increase the robustness of the system. In this presentation, I will discuss the results of my simulations, with an emphasis on the structure of the system, the slip mechanism, slip energetics and friction forces.

Theoretical Study of Ethylene Addition to O=W(=CH2)(CH3)2

2007 ◽  
Vol 62 (3) ◽  
pp. 367-372 ◽  
Author(s):  
Robin Haunschild ◽  
Gernot Frenking
Keyword(s):  
Density Functional ◽  
Theoretical Study ◽  
Activation Barrier ◽  
Reaction Pathways ◽  
Theoretical Studies ◽  
Stable Isomer ◽  
Functional Theory ◽  
B3lyp Level ◽  
Rhenium Compound ◽  
Favorable Reaction

Quantum chemical calculations using density functional theory at the B3LYP level of theory were carried out to investigate the reaction pathways for the addition of ethylene to WO(CH3)2(CH2) (W1). The results are compared to those of previous theoretical studies of the ethylene addition to OsO3(CH2) (Os1) and ReO2(CH3)(CH2) (Re1). The theoretically predicted reactions pathways exhibit significant differences. The energetically most favourable reaction of the tungsten system W1 is the [2+2]W,C addition across theW=C double bond yielding the metallacyclobutane W3a which then rearranges to the slightly more stable isomer W3b. The [2+2]Re,C addition of the rhenium compound yielding the metallacyclobutane Re3a has the lowest activation barrier for the ethylene addition to the rhenium system, but the reaction is endothermic while the exothermic formation of the more stable isomer Re3b has a much higher activation barrier. The [3+2]C,O addition Os1+C2H4→Os2 is the thermodynamically most favorable reaction of the osmium compound.

A theoretical study of the addition of CH2OO to hydroxymethyl hydroperoxide and its implications on SO3 formation in the atmosphere

2020 ◽  
Vol 22 (25) ◽  
pp. 14130-14141
Author(s):  
Ronald Chow ◽  
Daniel K. W. Mok
Keyword(s):  
Transition State ◽  
Quantum Chemical ◽  
Transition State Theory ◽  
Theoretical Study ◽  
State Theory ◽  
Chemical Methods ◽  
Quantum Chemical Methods ◽  
Indirect Source

The reaction of hydroxymethyl hydroperoxide with the simplest Criegee intermediate has been examined using quantum chemical methods with transition state theory. Results suggested that the reaction could be an indirect source of H2SO4 in atmosphere.

Synthesis of the New 2-Alkyl-nido-2,7,10-C3B8H11 Tricarbaborane by Protonation of [7-Alkyl-nido-7,8,10-C3B8H10]-: A Reversible Cage-Carbon Rearrangement

1999 ◽  
Vol 64 (5) ◽  
pp. 865-882 ◽  
Author(s):  
Alexandra M. Shedlow ◽  
Larry G. Sneddon
Keyword(s):  
Transition State ◽  
Activation Barrier ◽  
Original Position ◽  
Skeletal Rearrangement ◽  
Nmr Studies ◽  
Two Phase ◽  
Protonation Reaction ◽  
Pathway Activation ◽  
Incoming Proton ◽  
Open Face

Protonation of the [7-R-nido-7,8,10-C3B8H10]- (where R = PhCH2 (1a) or R = Me (1b)) tricarbollide anion, with concentrated H2SO4 in a two-phase aqueous/CH2Cl2 system, yields the new neutral tricarbaborane: 2-R-nido-2,7,10-C3B8H11 (where R = PhCH2 (2a) or R = Me (2b)). The three cage-carbons of the [7-R-nido-7,8,10-C3B8H10]- anion are located on the open face, but spectroscopic and DFT/GIAO/NMR studies of 2a and 2b show that during the protonation reaction, isomerization of the cage framework occurs to produce the neutral tricarbaborane having a 2,7,10-structure in which only two of the carbons remain on the open face. The third (R-substituted) carbon adopts a five-coordinate vertex off of the open face, thus enabling the incoming proton to adopt a bridging position on the B-B edge of the new C2B3-open face. The skeletal rearrangement is reversible, since deprotonation of 2a or 2b regenerates the anions 1a and 1b, respectively, having the 7,8,10-configuration. In agreement with the experimentally observed structures of the anionic (7,8,10-structure) and neutral (2,7,10-structure) species, DFT calculations at the B3LYP/6-311G*-level show that the [7-Me-nido-7,8,10-C3B8H10]- anion (1b, structure 16) is 28.9 kcal/mol more stable than the [2-Me-nido-2,7,10-C3B8H10]- isomer (3b, structure 18), while for the neutral tricarbaborane, the 2-R-nido-2,7,10-C3B8H11 (2b, structure 14) structure is more stable than any 7,8,10-structure (structures 7-11) which has the added proton in an endo position on the open face. Transition state calculations at the HF/6-31G*-level yielded a simple, low-energy pathway (activation barrier of only 6.5 kcal/mol for the transition state TS18/16) for the rearrangement of [2-Me-nido-2,7,10-C3B8H10]- (3b, structure 18) to [7-Me-nido-7,8,10-C3B8H10]- (1b, structure 16) requiring the movement of only one cage atom, B11, from its original position in the C7-B8-B9-C10-B11 plane of 3b, to the C7-C8-B9-C10-B11 plane of 1b.

Chiral Expression at the Solid−Liquid Interface: A Joint Experimental and Theoretical Study of the Self-Assembly of Chiral Porphyrins on Graphite

Langmuir ◽  
2008 ◽  
Vol 24 (17) ◽  
pp. 9566-9574 ◽  
Author(s):  
Mathieu Linares ◽  
Patrizia Iavicoli ◽  
Krystallia Psychogyiopoulou ◽  
David Beljonne ◽  
Steven De Feyter ◽  
...  
Keyword(s):  
Self Assembly ◽  
Theoretical Study ◽  
Liquid Interface ◽  
The Self ◽  
Solid Liquid Interface ◽  
Solid Liquid
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