Reaction of aniline with ammonium persulphate and concentrated hydrochloric acid: Experimental and DFT studies

2012 ◽  
Vol 66 (7) ◽  
Author(s):  
Maciej Przybyłek ◽  
Jerzy Gaca
Keyword(s):  
Density Functional ◽  
Main Product ◽  
Experimental Studies ◽  
Singlet Ground State ◽  
High Concentration ◽  
Functional Theory ◽  
Ammonium Persulphate ◽  
Orbital Population ◽  
Path Modelling ◽  
Reaction Path Modelling

AbstractIn this paper, the reaction of aniline with ammonium persulphate and concentrated HCl was studied. As a result of our experimental studies, 2,4,6-trichlorophenylamine was identified as the main product. This shows that a high concentration of HCl does not favour oxidative polymerisation of phenylamine, even though the ammonium persulphate/HCl system is widely used in polyaniline synthesis. On the basis of the experimental data and density functional theory for reaction path modelling, we proposed a mechanism for oxidative chlorination of aniline. We assumed that this reaction proceeded in three cyclically repeated steps; protonation of aniline, formation of singlet ground state phenylnitrenium cation, and nucleophilic substitution. In order to confirm this mechanism, kinetic, thermochemical, and natural bond orbital population analyses were performed.

Molecular Investigations of the Newly Synthesized Azomethines as Antioxidants: Theoretical and Experimental Studies

2019 ◽  
Vol 19 (6) ◽  
pp. 419-433 ◽  
Author(s):  
Siyamak Shahab ◽  
Masoome Sheikhi ◽  
Liudmila Filippovich ◽  
Evgenij Dikusar ◽  
Anhelina Pazniak ◽  
...  
Keyword(s):  
Density Functional ◽  
Energy Gap ◽  
Experimental Studies ◽  
Antioxidant Property ◽  
Nbo Analysis ◽  
Antioxidant Potential ◽  
Functional Theory ◽  
Homo And Lumo ◽  
Intramolecular Hydrogen ◽  
Activity Mechanism

: In this study, the antioxidant property of new synthesized azomethins has been investigated as theoretical and experimental. Methods and Results: Density functional theory (DFT) was employed to investigate the Bond Dissociation Enthalpy (BDE), Mulliken Charges, NBO analysis, Ionization Potential (IP), Electron Affinities (EA), HOMO and LUMO energies, Hardness (η), Softness (S), Electronegativity (µ), Electrophilic Index (ω), Electron Donating Power (ω-), Electron Accepting Power (ω+) and Energy Gap (Eg) in order to deduce scavenging action of the two new synthesized azomethines (FD-1 and FD-2). Spin density calculations and NBO analysis were also carried out to understand the antioxidant activity mechanism. Comparison of BDE of FD-1 and FD-2 indicate the weal antioxidant potential of these structures. Conclusion: FD-1 and FD-2 have very high antioxidant potential due to the planarity and formation of intramolecular hydrogen bonds.

Study on adsorption of CO and CO2 by graphene gas sensor

2021 ◽  
pp. 2150154
Author(s):  
Wenchao Tian ◽  
Jiahao Niu ◽  
Wenhua Li ◽  
Xiaohan Liu
Keyword(s):  
Gas Sensors ◽  
Active Sites ◽  
Density Functional ◽  
Gas Adsorption ◽  
Experimental Studies ◽  
Detection Accuracy ◽  
Functional Theory ◽  
Vacancy Defects ◽  
Adsorption Of Co ◽  
Detection Characteristics

The two-dimensional (2D) plane of graphene has many active sites for gas adsorption. It has broad application prospects in the field of MEMS gas sensors. At present, there are many experimental studies on graphene gas sensors, but it is difficult to accurately control various influencing factors in the experiments. Therefore, this paper applies the first principle based on density functional theory to study the adsorption and detection characteristics of graphene on CO and CO2. The first-principles analysis method was used to study the adsorption characteristics and sensitivity of graphene. The results show that the inductive graphene has a sensitivity of 1.55% and 0.77% for CO and CO2, respectively. The Stone–Wales defects and multi-vacancy defects have greatly improved the sensitivity of graphene to CO, which is 35.25% and 4.14%, respectively. Introduction of defects increases the sensitivity of detection of CO and CO2, but also improves the selective gas detection material of these two gases. Thus, the control and selectively introducing defects may improve the detection accuracy of the graphene CO and CO2.

scholarly journals Structural, elastic, electronic and thermal properties of InAs: A study of functional density

2017 ◽  
Vol 26 (46) ◽  
Author(s):  
Víctor Mendoza-Estrada ◽  
Melissa Romero-Baños ◽  
Viviana Dovale-Farelo ◽  
William López-Pérez ◽  
Álvaro González-García ◽  
...  
Keyword(s):  
Thermal Properties ◽  
Density Functional ◽  
Experimental Studies ◽  
Debye Model ◽  
Band Gap Energy ◽  
Functional Theory ◽  
Zinc Blende ◽  
The Density Functional Theory ◽  
The Stability ◽  
Experimental Values

In this research, first-principles calculations were carried out within the density functional theory (DFT) framework, using LDA and GGA, in order to study the structural, elastic, electronic and thermal properties of InAs in the zinc-blende structure. The results of the structural properties (a, B0, ) agree with the theoretical and experimental results reported by other authors. Additionally, the elastic properties, the elastic constants (C11, C12 and C44), the anisotropy coefficient (A) and the predicted speeds of the sound ( , , and ) are in agreement with the results reported by other authors. In contrast, the shear modulus (G), the Young's modulus (Y) and the Poisson's ratio (v) show some discrepancy with respect to the experimental values, although, the values obtained are reasonable. On the other hand, it is evident the tendency of the LDA and GGA approaches to underestimate the value of the band-gap energy in semiconductors. The thermal properties (V, , θD yCV) of InAs, calculated using the quasi-harmonic Debye model, are slightly sensitive as the temperature increases. According to the stability criteria and the negative value of the enthalpy of formation, InAs is mechanically and thermodynamically stable. Therefore, this work can be used as a future reference for theoretical and experimental studies based on InAs.

scholarly journals Influence of Varying Functionalization on the Peroxidase Activity of Nickel(II)–Pyridine Macrocycle Catalysts: Mechanistic Insights from Density Functional Theory

Computation ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 52
Author(s):  
Jerwin Jay E. Taping ◽  
Junie B. Billones ◽  
Voltaire G. Organo
Keyword(s):  
Density Functional Theory ◽  
Proton Transfer ◽  
Density Functional ◽  
Experimental Studies ◽  
Density Functional Theory Calculations ◽  
Catalytic Performance ◽  
Stoichiometric Ratio ◽  
Functional Theory ◽  
Pendant Arm ◽  
Spin Singlet

Nickel(II) complexes of mono-functionalized pyridine-tetraazamacrocycles (PyMACs) are a new class of catalysts that possess promising activity similar to biological peroxidases. Experimental studies with ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid), substrate) and H2O2 (oxidant) proposed that hydrogen-bonding and proton-transfer reactions facilitated by their pendant arm were responsible for their catalytic activity. In this work, density functional theory calculations were performed to unravel the influence of pendant arm functionalization on the catalytic performance of Ni(II)–PyMACs. Generated frontier orbitals suggested that Ni(II)–PyMACs activate H2O2 by satisfying two requirements: (1) the deprotonation of H2O2 to form the highly nucleophilic HOO−, and (2) the generation of low-spin, singlet state Ni(II)–PyMACs to allow the binding of HOO−. COSMO solvation-based energies revealed that the O–O Ni(II)–hydroperoxo bond, regardless of pendant arm type, ruptures favorably via heterolysis to produce high-spin (S = 1) [(L)Ni3+–O·]2+ and HO−. Aqueous solvation was found crucial in the stabilization of charged species, thereby favoring the heterolytic process over homolytic. The redox reaction of [(L)Ni3+–O·]2+ with ABTS obeyed a 1:2 stoichiometric ratio, followed by proton transfer to produce the final intermediate. The regeneration of Ni(II)–PyMACs at the final step involved the liberation of HO−, which was highly favorable when protons were readily available or when the pKa of the pendant arm was low.

THEORETICAL STUDIES ON THE REACTION MECHANISM OF HNCS WITH CH2CH RADICAL

2007 ◽  
Vol 06 (01) ◽  
pp. 1-12 ◽  
Author(s):  
JIAN-HUA XU ◽  
LAI-CAI LI ◽  
YAN ZHENG ◽  
JUN-LING LIU ◽  
XIN WANG
Keyword(s):  
Density Functional Theory ◽  
Reaction Mechanism ◽  
Reaction Mechanisms ◽  
Density Functional ◽  
Hydrogen Transfer ◽  
Main Product ◽  
Reaction Pathways ◽  
Theoretical Studies ◽  
Functional Theory ◽  
Ch Radical

The reaction mechanisms of HNCS with CH 2 CH radical have been investigated by density functional theory (DFT). The geometries and harmonic frequencies of the reactants, intermediates, transition states and products have been calculated at the B3LYP/6-311++G(d,p) level. The results show that the reaction is very complicated. Nine possible reaction pathways were identified. The results show that the most feasible reaction channel is the hydrogen-transfer pathway CH 2 CH + HNCS → IMA1 → TSA1 → CH 2 CHH + NCS . The pathway VIC C-S addition channel ( CH 2 CH + HNCS → TSD5 → IMD4 → TSD9 → CH 2 CHS + CNH ) can also occur easily. Ethene and radical NCS is the main product of the studied reaction, and product P8 ( CH 2 CHS and CNH ) may also be observed. Compared with our previous study on the reaction HNCS + CH 2 CH , the present reaction is easier to proceed.

A Density Functional Theory Study of Coniferyl Alcohol Intermonomeric Cross Linkages in Lignin - Three-Dimensional Structures, Stabilities and the Thermodynamic Control Hypothesis

Holzforschung ◽  
2003 ◽  
Vol 57 (2) ◽  
pp. 150-164 ◽  
Author(s):  
B. Durbeej ◽  
L.A. Eriksson
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Structural Features ◽  
Density Functional Theory Study ◽  
Thermodynamic Control ◽  
Functional Theory ◽  
Quantitative Correlation ◽  
Control Hypothesis

Summary Density functional theory methods are utilized to investigate structural features and stabilities of the most common lignin dimerization products. It is found that intra-molecular hydrogen bonding acts as a stabilizing force in the lowest-energy conformer(s) of several different dimeric lignin structures. Furthermore, the calculations show that the hypothesis of thermodynamic control of monolignol dimerization accounts for some of the results obtained in experimental studies aimed at determining the ratios of intermonomeric linkages. A quantitative correlation between experimentally observed ratios and calculated relative energies cannot, however, be pointed out.

Combined Computational and Experimental Studies of Trans- and Cis-Isomers of Potassium Diaquabis(Oxalato)Chromate (III)

2017 ◽  
Vol 757 ◽  
pp. 103-107
Author(s):  
Songtham Ruangchaithaweesuk ◽  
Juthathip Chorkate ◽  
Thana Maihom ◽  
Potjaman Poolmee ◽  
Piti Treesukol ◽  
...  
Keyword(s):  
Excited States ◽  
Density Functional ◽  
Experimental Studies ◽  
Relative Energy ◽  
Time Dependent ◽  
Dft Methods ◽  
Functional Theory ◽  
Stable Forms ◽  
Tddft Method ◽  
Dependent Density

The trans- and cis-isomers of potassium diaquabis(oxalato)chromate (III) were studied computationally and experimentally. The structures of trans- and cis-configurations of [Cr(H2O)2(C2O4)2]- were optimized by DFT methodology with various functionals namely: B3LYP, CAM-B3LYP, TPSS, PBE, M06-L and ωB97X-D along with the more sophisticated MP2 method. The calculations show that the most stable forms for both isomers are in quartet states. The results from all DFT methods reveal that the cis-isomer is literally more stable than the trans-isomer with the lower average relative energy of 2.1 kcal/mol. These are consistent with the results from MP2 calculation and experimental observation. The absorption wavelengths for the excited states of trans- and cis-structures were calculated by the time-dependent density functional theory (TDDFT) method. For the experiments, the trans- and cis-isomers of potassium diaquabis(oxalato)chromate (III) were synthesized and characterized by UV-Vis spectrophotometry. Both isomers have two maximum absorption wavelengths at 415 and 560 nm.

Development of a Suite of Computational Models for the Design of Ultralow-k SiCOH-based Materials

2012 ◽  
Vol 1428 ◽  
Author(s):  
Alexandra Cooper ◽  
Paulette Clancy
Keyword(s):  
Mechanical Properties ◽  
Density Functional ◽  
Computational Models ◽  
Experimental Studies ◽  
Atomic Scale ◽  
Scale Model ◽  
Simple Correlation ◽  
Functional Theory ◽  
Mechanical And Electrical Properties ◽  
Multiple Length Scales

ABSTRACTA computational model of amorphous SiCOH materials is described that will facilitate studies of SiCOH behavior under different thermal and mechanical stresses. This involved developing an atomic-scale model of an SiCOH thin film, which exhibited structural, mechanical and electrical properties in agreement with experimental studies. We developed a unique process for computationally creating the structure of SiCOH films. We created an algorithm for introducing and estimating porosity in the system, which provides detailed information about the system’s pore size distribution on multiple length scales. We used Density Functional Theory (DFT) to develop a simple correlation that calculates the dielectric constant of a large SiCOH structure based only on its atomic composition and volume. Finally, we confirmed the mechanical properties of the model using established Molecular Dynamics techniques. We verified that essential electronic and mechanical properties of the model structure reproduce experimental data for a representative SiCOH material within acceptable accuracy. We find the mechanical properties are significantly weakened by the presence of pendant carbon groups.

Differences in chemical properties and reactivity patterns of mono- and dioxomanganese(V) porphyrins as revealed by density functional theory

2013 ◽  
Vol 17 (10) ◽  
pp. 954-963 ◽  
Author(s):  
Sam P. de Visser
Keyword(s):  
Density Functional Theory ◽  
Ligand Exchange ◽  
Density Functional ◽  
Experimental Studies ◽  
Chemical Properties ◽  
Hydrogen Atom Abstraction ◽  
Functional Theory ◽  
Orbital Interactions ◽  
Catalytic Potential ◽  
Unique Mechanism

Recent experimental studies of Liu and Groves (J. Am. Chem. Soc. 2010; 132: 12847) on dioxomanganese(V) porphyrin complexes implicated substrate halogenation in good yield. Currently, little is known of this unique mechanism, therefore to gain understanding on the halogenation mechanism and the chemical features of this oxidant we decided to do a computational (density functional theory) study. We show that the dioxomanganese(V) complex has considerably different molecular (valence) orbitals as compared to monooxomanganese(V) porphyrin due to mixing of the metal 3d orbitals with 2p orbitals on both oxygen atoms. This results in a set of three pairs of orbitals of which the bonding and nonbonding pairs are doubly occupied and the antibonding orbitals are vacant. As a consequence, the bonding character along the Mn–O bond is less in dioxomanganese(V) as compared to monooxomanganese(V) complexes and therefore this bond can formally be described as a double bond rather than a triple bond. The differences in orbital interactions and orbital energies also affect the intrinsic chemical properties of the oxidants, such as the electron affinity and pKa values, which result in enhanced catalytic potential for dioxomanganese(V) porphyrin. Our calculations predict a halogenation mechanism in line with that proposed by experiment with an initial hydrogen atom abstraction followed by ligand exchange and halogen transfer.

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