scholarly journals ab initio Method on the Mechanism of Acetalization of 2-Methoxybenzaldehyde Using Halogen Acid Catalysts

2019 ◽  
Vol 31 (5) ◽  
pp. 982-986 ◽  
Author(s):  
Muhammad Yusuf ◽  
Dahniar ◽  
Destria Roza ◽  
Marini Damanik
Keyword(s):  
Reaction Mechanism ◽  
Ab Initio ◽  
Approximate Calculation ◽  
Basis Set ◽  
Quantum Mechanical ◽  
Acid Catalysts ◽  
Ab Initio Method ◽  
Neighbour Atom ◽  
Computational Calculation ◽  
Halogen Acid

ab initio method used on the mechanism of acetalization of 2-methoxybenzaldehyde. ab initio method is a quantum mechanical approximate calculation and derived directly only from theoretical principles. All geometry optimizations were performed using 3-21G and 6-31G* basis set with Hyperchem 8.0 software (windows version). The aim of this study was to focus on the study of the mechanism of acetalization of 2-methoxybenzaldehyde using hydrochloric acid as catalysts. The computational calculation not only provided possible reaction steps but also provided possible energy change in each step of the reaction mechanism of acetalization of 2-methoxybenzaldehyde. The result showed that 2-methoxybenzaldehyde (0 kJ/mol) has the lowest energy and electronegativity compared to acetal product (-17.43 kJ/mol) and a labile hemiacetal (448.33 kJ/mol) due to its stability and the influence of neighbour atom.

scholarly journals Ab initio study of the mechanism of the reaction ClO + O --> Cl + O2

2021 ◽  
Vol 66 (1) ◽  
Author(s):  
S. Naskar ◽  
G. Nandi ◽  
T. K. Ghosh
Keyword(s):  
Reaction Mechanism ◽  
Ab Initio ◽  
Minimum Energy ◽  
Transition States ◽  
Basis Set ◽  
Heat Of Reaction ◽  
Minimal Basis ◽  
Dissociation Energies ◽  
Correlation Consistent ◽  
Equilibrium Geometries

Abstract. Ab initio investigation on the reaction mechanism of ClO + O --> Cl + O2 reaction has been performed using correlation consistent triple zeta basis set. The geometry and frequency of the reactants, products, minimum energy geometries and transition states are obtained using MP2 method and energetics are obtained at the QCISD(T)//MP2 level of theory. Primarily, a possible reaction mechanism is obtained on the basis on IRC calculations using MP2 level of theory. To obtain true picture of the reaction path, we performed IRC calculations using CASSCF method with a minimal basis set 6-31G**. Some new equilibrium geometries and transition states have been identified at the CASSCF level. Energetics are also obtained at the QCISD(T)//CASSCF method. Possible reaction paths have been discussed, which are new in literature. Heat of reaction is found to be consistent with the experimental data. Bond dissociation energies to various dissociation paths are also reported.

A Theoretical Structure Study Infrared Spectra of C60O Isomers Through Ab Initio Method

2011 ◽  
Vol 2 (1) ◽  
Author(s):  
Rashid Nizam ◽  
S. Mahdi A. Rizvi ◽  
Ameer Azam
Keyword(s):  
Ab Initio ◽  
Infrared Spectra ◽  
Structure Study ◽  
Basis Set ◽  
Ab Initio Method ◽  
Single Experiment ◽  
Theoretical Structure ◽  
Semi Empirical ◽  
Isomeric Structures ◽  
Neglect Of Differential Overlap

The infrared spectra of C60O isomers have been calculated through ab initio method. It has been observed that the simulated spectrum of one of C60O isomers is matching with the available experimental data in literature, while the other isomers are not matching so much. One can easily understand the basic physical properties of C60O by knowing of their vibration and geometric structures with their interrelation between these properties. It is found that the isomeric structures of C60O are very sensitive to electron correlation treatment with basis set that are employed. So the structure of C60O will not calculate from semi-empirical methods such as modified neglect of differential overlap (MNDO) or AM1 for more accuracy. The simulated spectra show different bands that rarely found all bands simultaneously in single experiment.

Quantum mechanical tunnelling through the catalytic effects of A2451 ribosomal residue during a stepwise peptide bond formation

2019 ◽  
Vol 97 (4) ◽  
pp. 497-503
Author(s):  
Hadieh Monajemi ◽  
Sharifuddin Md. Zain ◽  
Toshimasa Ishida ◽  
Wan Ahmad Tajuddin Wan Abdullah
Keyword(s):  
Reaction Mechanism ◽  
Proton Transfer ◽  
Density Functional ◽  
Bond Formation ◽  
Peptide Bond ◽  
State Theory ◽  
Basis Set ◽  
Quantum Mechanical ◽  
Peptide Bond Formation ◽  
Quantum Mechanical Effects

The search for the mechanism of ribosomal peptide bond formation is still ongoing. Even though the actual mechanism of peptide bod formation is still unknown, the dominance of proton transfer in this reaction is known for certain. Therefore, it is vital to take the quantum mechanical effects on proton transfer reaction into consideration; the effects of which were neglected in all previous studies. In this study, we have taken such effects into consideration using a semi-classical approach to the overall reaction mechanism. The M06-2X density functional with the 6-31++G(d,p) basis set was used to calculate the energies of the critical points on the potential energy surface of the reaction mechanism, which are then used in transition state theory to calculate the classical reaction rate. The tunnelling contribution is then added to the classical part by calculating the transmission permeability and tunnelling constant of the reaction barrier, using the numerical integration over the Boltzmann distribution for the symmetrical Eckart potential. The results of this study, which accounts for quantum effects, indicates that the A2451 ribosomal residue induces proton tunnelling in a stepwise peptide bond formation.

scholarly journals Theoretical determination of the favorable mechanism of the reaction between AlX and HX (X = Br, Cl, and F)

2009 ◽  
Vol 7 (3) ◽  
pp. 328-336
Author(s):  
Mustapha Cherkaoui ◽  
Abderrahim Boutalib
Keyword(s):  
Reaction Mechanism ◽  
Ab Initio ◽  
Molecular Hydrogen ◽  
Ab Initio Method ◽  
Theoretical Determination ◽  
Insertion Product ◽  
Mechanism Of The Reaction

AbstractThe reaction mechanism between AlX and HX (X = Br, Cl, and F) have been characterized in detail using DFT as well as the ab initio method. The reaction yielding AlX3 and molecular hydrogen was calculated to be highly exothermic. The present calculations also show that the possible routes to the trihalides species start more favorable with the primary insertion product AlX2H than with the biadduct AlX(HX)2 one.

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