scholarly journals Theoretical Investigation of the Hydrolytic Mechanism of α-Functionalized Alkoxysilanes as Effective Crosslinkers and the Difficulty of Deep Vulcanization in RTV Silicone Rubber

Materials ◽  
2018 ◽  
Vol 11 (9) ◽  
pp. 1526
Author(s):  
Huihui Xu ◽  
Yanhong Gao ◽  
Zihou Liu ◽  
Yiling Bei
Keyword(s):  
Density Functional Theory ◽  
Silicone Rubber ◽  
Density Functional ◽  
Room Temperature ◽  
Reaction Pathway ◽  
Stationary Points ◽  
Functional Theory ◽  
Hydrolytic Mechanism ◽  
Hydrolysis Activity ◽  
Rtv Silicone Rubber

The reactions between α-, γ-ethylenediaminemethyl trimethyl-ketoxime silane (α-, γ-EAMOS) and H2O were investigated on the geometries of stationary points, the reaction pathway (IRC), thermodynamic and kinetic analysis by density functional theory (DFT) at the B3LYP/6-311G (d, p) level. Interestingly, the results showed that the hydrolysis activity of α-EAMOS is higher than that of γ-EAMOS, due to the influence of an amino substituent in position α-C on silicon. α-EAMOS can be used as a superior crosslinker for room temperature vulcanized (RTV) silicone rubber to achieve rapid crosslinking without a toxic catalyst. Besides, compared with the reaction between α-EAMOS and H2O, the reactivity between α-EAMOS and hydroxy siloxane (HO–Si(CH3)2–OSiH3) was discussed. Particularly, it revealed that the deep vulcanization of RTV silicone rubber is difficult.

Synthesis of novel N-functionalized 4-aryl-tetrahydrobiquinoline-2,5-(1H,3H)-diones via one-pot three-component reaction: a joint experimental and computational study

2018 ◽  
Vol 96 (12) ◽  
pp. 1071-1078
Author(s):  
Vahideh Zadsirjan ◽  
Sayyed Jalil Mahdizadeh ◽  
Majid M. Heravi ◽  
Masumeh Heydari
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Computational Study ◽  
Reaction Pathway ◽  
Deep Insight ◽  
One Pot ◽  
Functional Theory ◽  
Three Component Reaction ◽  
High Yields ◽  
Mechanism Of The Reaction

A novel series of N-functionalized 4-aryl-tetrahydrobiquinoline-2,5-(1H,3H)-diones were synthesized in high yields by a one-pot three-component reaction involving 2-chloroquinoline-3-carbaldehydes, Meldrum’s acid, and enaminones (dimedone-based enaminones) in the presence of K2CO3 in CH3CN under reflux condition. To gain a deep insight on the mechanism of the reaction, an extensive series of quantum mechanics calculations in the framework of density functional theory (DFT) were carried out for supporting the suggested reaction pathway.

Twisted Push - Pull Ethylenes

2008 ◽  
Vol 61 (10) ◽  
pp. 805 ◽  
Author(s):  
Rakesh Naduvile Veedu ◽  
Paul V. Bernhardt ◽  
Rainer Koch ◽  
Curt Wentrup
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Room Temperature ◽  
Dihedral Angles ◽  
Functional Theory ◽  
Activation Barriers ◽  
Rapid Rotation ◽  
X Ray ◽  
X Ray Crystallography ◽  
Calculated Activation

As determined by X-ray crystallography, Meldrum’s acid derivatives 5, 6, and 8 feature dihedral angles around the central C5=C7 double bond of 14–35°, whereas for the anion 9 this angle is 90°. Density functional theory and MP2 calculations are in agreement with the experimental X-ray data for compounds 5–8, but for anion 9 an angle of only ~65° is predicted. It is concluded that a part of the torsion is due to packing forces in the crystal. It is further concluded that these molecules undergo rapid rotation about the central CC bonds at room temperature (calculated activation barriers 5–14 kcal mol–1).

scholarly journals Density Functional Theory Based Micro- and Macro-Kinetic Studies of Ni-Catalyzed Methanol Steam Reforming

Catalysts ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 349 ◽  
Author(s):  
Changming Ke ◽  
Zijing Lin
Keyword(s):  
Density Functional Theory ◽  
Steam Reforming ◽  
Density Functional ◽  
Reaction Pathway ◽  
Elementary Reaction ◽  
Main Reaction ◽  
Methanol Steam Reforming ◽  
Surface Species ◽  
Functional Theory ◽  
Microkinetic Model

The intrinsic mechanism of Ni-catalyzed methanol steam reforming (MSR) is examined by considering 54 elementary reaction steps involved in MSR over Ni(111). Density functional theory computations and transition state theory analyses are performed on the elementary reaction network. A microkinetic model is constructed by combining the quantum chemical results with a continuous stirring tank reactor model. MSR rates deduced from the microkinetic model agree with the available experimental data. The microkinetic model is used to identify the main reaction pathway, the rate determining step, and the coverages of surface species. An analytical expression of MSR rate is derived based on the dominant reaction pathway and the coverages of surface species. The analytical rate equation is easy to use and should be very helpful for the design and optimization of the operating conditions of MSR.

The Local Structure and I-V Characteristics of Chromium Doped Semiconducting Boron Carbide

2011 ◽  
Vol 1307 ◽  
Author(s):  
Jing Liu ◽  
P. A. Dowben ◽  
Guangfu Luo ◽  
Wai-Ning Mei ◽  
Anil Kumar Rajapitamahuni ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Boron Carbide ◽  
Local Structure ◽  
Density Functional ◽  
Room Temperature ◽  
Magnetic Ordering ◽  
Computational Results ◽  
Functional Theory ◽  
Spin Configuration ◽  
Current Voltage

ABSTRACTThe local spin configuration and band structure of chromium doped boron carbide calculated by density functional theory suggests local magnetic ordering. While the long range dopant position appears random in the boron carbide semiconductor, the local position and initial empirical/computational results suggest the promise of large magneto-resistive effects. The chromium doped boron carbide thin films, fabricated by boron carbide-chromium co-deposition, were studied by current-voltage (I-V) characteristics measurements. The results provide some reason to believe that magneto-resistive effects are indeed present at room temperature.

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