scholarly journals Methane Activation by CoOₘⁿ⁺ (n = 0, 1, 2; m= 1, 2): Reactivity Parameters, Electronic Properties and Binding Energy Analysis

2019 ◽  
Author(s):  
Teodorico Ramalho
Keyword(s):  
Bond Activation ◽  
Theoretical Calculations ◽  
Low Cost ◽  
Activation Process ◽  
High Electron ◽  
Central Metal ◽  
Insertion Mechanism ◽  
Binding Energy Analysis ◽  
Homo And Lumo ◽  
Doubly Charged

<p>The need for renewal, more efficient and conscious usage of energy resources has led to a great interest in carrying out studies aiming to find novel sources of energy, which are able to supply the growing global demand, and at the same time, providing an ecofriendly usage of natural resources. In this context, the usage of methane stands out as a promising energetic alternative for this goal, mostly due to the existence of vast reserves, its low cost and less polluting fuel. For theoretical calculations B3LYP, CCSD(t) and ZORA-B3LYP methods were used to look into the catalytic properties of (CoOₘⁿ⁺ n= 0, 1, 2 and m=1, 2) in the methane C-H bond activation. According to the EDA outcomes, the studied species presented two stabilizing factors for the global interaction energy, being the electrostatic ΔE<sub>elstat</sub> and orbital ΔE<sub>orb</sub> interactions. The HOMO and LUMO orbitals were also evaluated based on the molecular orbital diagrams for the monoxides and dioxides series. Regarding the oxidative insertion mechanism, the outcomes demonstrate that the initial interaction between oxide and methane is of great relevance in its activation process, in which E<sub>Bonding</sub> is benefited by the increasingly charge on the central metal. The high electron density regarding the oxides is meaningful for the reaction kinetics and the oxo ligands influence the thermodynamics of the reaction, becoming the DHA mechanism exergonic. Regarding the OHM mechanism, better kinetic conditions are found for CoO2<sup>++</sup> and better thermodynamics for doubly charged cobalt monoxides and dioxides.</p>

scholarly journals Methane Activation by CoOₘⁿ⁺ (n = 0, 1, 2; m= 1, 2): Reactivity Parameters, Electronic Properties and Binding Energy Analysis

2019 ◽  
Author(s):  
Teodorico Ramalho
Keyword(s):  
Bond Activation ◽  
Theoretical Calculations ◽  
Low Cost ◽  
Activation Process ◽  
High Electron ◽  
Central Metal ◽  
Insertion Mechanism ◽  
Binding Energy Analysis ◽  
Homo And Lumo ◽  
Doubly Charged

<p>The need for renewal, more efficient and conscious usage of energy resources has led to a great interest in carrying out studies aiming to find novel sources of energy, which are able to supply the growing global demand, and at the same time, providing an ecofriendly usage of natural resources. In this context, the usage of methane stands out as a promising energetic alternative for this goal, mostly due to the existence of vast reserves, its low cost and less polluting fuel. For theoretical calculations B3LYP, CCSD(t) and ZORA-B3LYP methods were used to look into the catalytic properties of (CoOₘⁿ⁺ n= 0, 1, 2 and m=1, 2) in the methane C-H bond activation. According to the EDA outcomes, the studied species presented two stabilizing factors for the global interaction energy, being the electrostatic ΔE<sub>elstat</sub> and orbital ΔE<sub>orb</sub> interactions. The HOMO and LUMO orbitals were also evaluated based on the molecular orbital diagrams for the monoxides and dioxides series. Regarding the oxidative insertion mechanism, the outcomes demonstrate that the initial interaction between oxide and methane is of great relevance in its activation process, in which E<sub>Bonding</sub> is benefited by the increasingly charge on the central metal. The high electron density regarding the oxides is meaningful for the reaction kinetics and the oxo ligands influence the thermodynamics of the reaction, becoming the DHA mechanism exergonic. Regarding the OHM mechanism, better kinetic conditions are found for CoO2<sup>++</sup> and better thermodynamics for doubly charged cobalt monoxides and dioxides.</p>

Analysis of the UV Absorption Band of Cephalosporins

1992 ◽  
Vol 46 (1) ◽  
pp. 44-48 ◽  
Author(s):  
B. Vilanova ◽  
F. Muñoz ◽  
J. Donoso ◽  
F. Garcia Blanco
Keyword(s):  
Ground State ◽  
Theoretical Calculations ◽  
High Electron ◽  
Ph Values ◽  
Medium Polarity ◽  
Electron Transitions ◽  
Homo And Lumo ◽  
The Stability ◽  
Experimental Values ◽  
Log Normal

We studied the absorption spectrum of 7-aminocephalosporanic acid between 312 and 238 nm (32,000–42,000 cm−1) at different pH values. The spectrum was deconvoluted into log-normal curves that showed three different transitions; the first two bands are due to π-π* transitions between the HOMO and LUMO, and from the HOMO to the LUMO + 1, respectively. We also recorded the spectrum of the acid in dioxane/water mixtures and found band I to shift to shorter wavelengths with an increase in the medium polarity. Theoretical calculations allowed us to ascribe this behavior to the fact that the β-lactam nitrogen atom possesses a high electron density in the ground state. As the medium polarity increases, so does the stability of this state, which results in the band being shifted to higher energy values. The theoretical calculations (MNDO) performed yielded 36.8 and 39.8 kK (1 kK = 103 cm−1) for the first two electron transitions, i.e., very close to the experimental values (∼36 and 39 kK).

Theoretical and experimental studies of palladium-catalyzed site-selective C(sp3)−H bond functionalization enabled by transient ligands

2017 ◽  
Author(s):  
Haibo Ge ◽  
Lei Pan ◽  
Piaoping Tang ◽  
Ke Yang ◽  
Mian Wang ◽  
...  
Keyword(s):  
Bond Activation ◽  
Theoretical Calculations ◽  
Experimental Studies ◽  
Bond Functionalization ◽  
Aliphatic Ketones ◽  
Site Selectivity ◽  
Mechanistic Investigation ◽  
Palladium Catalyzed ◽  
Metal Catalyzed ◽  
Site Selective

Transition metal-catalyzed selective C–H bond functionalization enabled by transient ligands has become an extremely attractive topic due to its economical and greener characteristics. However, catalytic pathways of this reaction process on unactivated sp<sup>3</sup> carbons of reactants have not been well studied yet. Herein, detailed mechanistic investigation on Pd-catalyzed C(sp<sup>3</sup>)–H bond activation with amino acids as transient ligands has been systematically conducted. The theoretical calculations showed that higher angle distortion of C(sp2)-H bond over C(sp3)-H bond and stronger nucleophilicity of benzylic anion over its aromatic counterpart, leading to higher reactivity of corresponding C(sp<sup>3</sup>)–H bonds; the angle strain of the directing rings of key intermediates determines the site-selectivity of aliphatic ketone substrates; replacement of glycine with β-alanine as the transient ligand can decrease the angle tension of the directing rings. Synthetic experiments have confirmed that β-alanine is indeed a more efficient transient ligand for arylation of β-secondary carbons of linear aliphatic ketones than its glycine counterpart.<br><br>

scholarly journals MANUFACTURE OF A DIE PROTOTYPE FOR DIDACTIC PURPOSES IN MECHATRONIC ENGINEERING

2020 ◽  
pp. 1-40
Author(s):  
ELIEL EDUARDO MONTIJO-VALENZUELA ◽  
SAUL DANIEL DURAN-JIMENEZ ◽  
LUIS ALBERTO ALTAMIRANO-RÍOS ◽  
JOSÉ ISAEL PÉREZ-GÓMEZ ◽  
OSCAR SALMÓN-AROCHI
Keyword(s):  
Mechanical Design ◽  
Theoretical Calculations ◽  
Low Cost ◽  
Die Design ◽  
Element Analysis ◽  
Technological Institute ◽  
Computer Aided ◽  
Cad Models ◽  
Functional Prototype ◽  
Definition Of

The objective of this research is to manufacture a prototype of a teaching die for the specialty of precision mechanical design in mechatronic engineering, in order to achieve the skills required in unit two, regarding dies. The methodology used consists of five stages: 1. Definition of the preliminary conditions. 2. Theoretical calculations for die design. 3. Design, modeling and assembly using computer-aided software (CAD) of the parts that make up the die. 4. Validation with simulation of finite element analysis (AEF). 5. Manufacture of parts and physical assembly of the die. A functional prototype was obtained with which the teacher and student can perform calculations, designs and CAD models, AEF analysis of the static and fatigue type, manufacture of rapid prototypes using 3D printing, the identification of the parts that make up a die and their functioning. The advantage of this prototype, compared to metal die-cutting machines, is its low cost of production and manufacturing, it does not require expensive and specialized machinery for manufacturing, specific designs can be made by the students and its subsequent manufacture within the laboratories of the Technological Institute of Hermosillo.

scholarly journals Preparation of Cerium Oxide-MWCNTs Nanocomposite Bulk Modified Carbon Ceramic Electrode: A Sensitive Sensor for Tamoxifen Determination in Human Serum Samples

2021 ◽  
Author(s):  
Sepideh Shafaei ◽  
Elyas Hosseinzadeh ◽  
Gulsah Saydan Kanberoglu ◽  
Balal Khalilzadeh ◽  
Rahim Mohammad-Rezaei
Keyword(s):  
Cerium Oxide ◽  
Limit Of Detection ◽  
Low Cost ◽  
High Electron ◽  
Range Limit ◽  
Serum Samples ◽  
Important Species ◽  
Carbon Ceramic Electrode ◽  
Carbon Ceramic

Abstract In this study, cerium oxide and multi-walled carbon nanotubes nanocomposite was incorporated into the carbon ceramic electrode (CeO2-MWCNTs/CCE) as a renewable electrode for the electrocatalytic purposes. To demonstrate capability of the fabricated electrode, determination of Tamoxifen as an important anticancer drug with differential pulse voltammetry technique was evaluated. Linear range, limit of detection and sensitivity of the developed sensor were found to be 0.2-40 nM, 0.132 nM and 1.478 µA nM-1 cm-2, respectively. Ease of production, low cost and high electron transfer rate of CeO2-MWCNTs/CCE promise it as a novel electro-analytical tool for determination of important species in real samples.

scholarly journals Synthesis and Characterisation of Pyridinium-Based Ionic Liquid as Activating Agent in Rubber Seed Shell Activated Carbon Production for CO2 Capture

2021 ◽  
Vol 82 (1) ◽  
pp. 85-95
Author(s):  
Nawwarah Mokti ◽  
Azry Borhan ◽  
Siti Nur Azella Zaine ◽  
Hayyiratul Fatimah Mohd Zaid
Keyword(s):  
Ionic Liquid ◽  
Activated Carbon ◽  
Adsorption Capacity ◽  
Co2 Capture ◽  
Low Cost ◽  
Chemical Activation ◽  
Green Technology ◽  
Activation Process ◽  
Rubber Seed ◽  
Activating Agent

The use of an activating agent in chemical activation of activated carbon (AC) production is very important as it will help to open the pore structure of AC as adsorbents and could enhance its performance for adsorption capacity. In this study, a pyridinium-based ionic liquid (IL), 1-butylpyridinium bis(trifluoromethylsulfonyl) imide, [C4Py][Tf2N] has been synthesized by using anion exchange reaction and was characterized using few analyses such as 1H-NMR, 13C-NMR and FTIR. Low-cost AC was synthesized by chemical activation process in which rubber seed shell (RSS) and ionic liquid [C4Py][Tf2N] were employed as the precursor and activating agent, respectively. AC has been prepared with different IL concentration (1% and 10%) at 500°C and 800°C for 2 hours. Sample AC2 shows the highest SBET and VT which are 392.8927 m2/g and 0.2059 cm3/g respectively. The surface morphology of synthesized AC can be clearly seen through FESEM analysis. A high concentration of IL in sample AC10 contributed to blockage of pores by the IL. On the other hand, the performance of synthesized AC for CO2 adsorption capacity also studied by using static volumetric technique at 1 bar and 25°C. Sample AC2 contributed the highest CO2 uptakes which is 50.783 cm3/g. This current work shows that the use of low concentration IL as an activating agent has the potential to produce porous AC, which offers low-cost, green technology as well as promising application towards CO2 capture.

Theoretical study of first row transitional metals effects on stabilization of verdoheme analogues

2019 ◽  
Vol 23 (10) ◽  
pp. 1100-1109
Author(s):  
Afsaneh Taghizadeh ◽  
Maryam Daghighi Asli ◽  
Parisa Rajabali Jamaat
Keyword(s):  
Chemical Potential ◽  
Dft Method ◽  
Basis Set ◽  
Orbital Energy ◽  
Central Metal ◽  
Transitional Metals ◽  
Solvent Phase ◽  
Energy Formula ◽  
Homo And Lumo

Heme catabolism is an important physiological process that converts heme to biliverdin in the presence of heme oxygenase which has an essential role in destroying unwanted heme. Verdohemes, the green iron (II) complexes of the 5-oxaporphyrin macrocycle are produced by oxidative destruction of heme. The main goal of this study is clarification of the central metal effect on stabilization of metal 5-oxaporphyrin molecules. To investigate the role of central metal on geometric and electronic properties of five coordinated verdoheme analogues, the first row transitional metals, including Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn, as the central metal of five-coordinated metal 5-oxaporphyrins were systematically calculated without any symmetry constraint by using the B3LYP as DFT method and the 6-31G basis set in gas and solvent phases. According to the results, the stabilization energy of metal 5-oxaporphyrins increases with atomic mass in the solvent phase more than in the gas phase. By reviewing the properties such as the computed frontier orbital energy, HOMO and LUMO gap energy [Formula: see text], hardness [Formula: see text], chemical potential [Formula: see text], softness (s) and electrophilicity [Formula: see text], the pharmaceutical use of this compound can be discussed.

Adsorptive Removal of Pb(II) Ion from Aqueous Solution Using Rice Husk-Based Activated Carbon

2014 ◽  
Vol 875-877 ◽  
pp. 196-201 ◽  
Author(s):  
Mohd Faisal Taha ◽  
Ahmad S. Rosman ◽  
Maizatul S. Shaharun
Keyword(s):  
Aqueous Solution ◽  
Activated Carbon ◽  
Rice Husk ◽  
Low Cost ◽  
Chemical Activation ◽  
Textural Properties ◽  
Activation Process ◽  
Adsorption Studies ◽  
Three Samples ◽  
Equilibrium Data

The potential of rice husk-based activated carbon as an alternative low-cost adsorbent for the removal of Pb (II) ion from aqueous solution was investigated. Rice husk-based activated carbon was preparedviachemical activation process using NaOH followed by the carbonization process at 500°C. Morphological analysis was conducted using field-emission scanning electron microscope /energy dispersive X-ray (FESEM/EDX) on three samples, i.e. raw rice husk, rice husk treated with NaOH and rice husk-based activated carbon. These three samples were also analyzed for their C, H, N, O and Si contents using CHN elemental analyzer and FESEM/EDX. The textural properties of rice husk-based activated carbon, i.e. surface area (253 m2/g) and pore volume (0.17 cm2/g), were determined by N2adsorption. The adsorption studies using rice husk-based activated carbon as an adsorbent to remove Pb (II) ion from aqueous solution were carried out at a fixed initial concentration of Pb (II) ion (150 ppm) with varying adsorbent dose as a function of contact time at room temperature. The concentration of Pb (II) ion was determined by atomic absorption spectrophotometer (AAS). The removal of Pb (II) ion from aqueous solution increased from 35 % to 82 % when the amount of rice husk-based activated carbon was increased from 0.05 g to 0.30 g. The equilibrium data obtained from adsorption studies was found to fit both Langmuir and Freundlich adsorption isotherms.

Carbon Dioxide-Driven Palladium-Catalyzed C–H Activation of Amines: A Unified Approach for the Arylation of Aliphatic and Aromatic Primary and Secondary Amines

Synlett ◽  
2019 ◽  
Vol 30 (05) ◽  
pp. 519-524 ◽  
Author(s):  
Michael Young ◽  
Mohit Kapoor ◽  
Pratibha Chand-Thakuri ◽  
Justin Maxwell ◽  
Daniel Liu ◽  
...  
Keyword(s):  
Carbon Dioxide ◽  
Bond Activation ◽  
Secondary Amines ◽  
Activation Process ◽  
Unified Approach ◽  
Benzylic Amines ◽  
Palladium Catalyzed ◽  
Group A ◽  
Directing Group ◽  
Site Selective

Amines are an important class of compounds in organic chemistry and serve as an important motif in various industries, including pharmaceuticals, agrochemicals, and biotechnology. Several methods have been developed for the C–H functionalization of amines using various directing groups, but functionalization of free amines remains a challenge. Here, we discuss our recently developed carbon dioxide driven highly site-selective γ-arylation of alkyl- and benzylic amines via a palladium-catalyzed C–H bond-activation process. By using carbon dioxide as an inexpensive, sustainable, and transient directing group, a wide variety of amines were arylated at either γ-sp3 or sp2 carbon–hydrogen bonds with high selectivity based on substrate and conditions. This newly developed strategy provides straightforward access to important scaffolds in organic and medicinal chemistry without the need for any expensive directing groups.1 Introduction2 C(sp3)–H Arylation of Aliphatic Amines3 C(sp2)–H Arylation of Benzylamines4 Mechanistic Questions5 Future Outlook

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