Search for: chemical-reactions
Total 153 records
Article Surface Review and Letters ; Volume 10, Issue 6 , 2003 , Pages 895-901 ; 0218625X (ISSN) ; Gobal, F ; Sharif University of Technology
The method of unity bond index-quadratic exponential potential (UBI-QEP) is employed to derive the energetic parameters associated with the steps of the pathway which we propose for the catalytic decomposition of azomethane on the Pd(111) surface. According to the energy calculations, azomethane adsorbs molecularly in trans-configuration and then decomposes to CH3N with no activation energy. The reaction continues by tilting and dehydrogenation to the products (H2 and HCN). The calculated activation energies at various surface coverages perfectly account for the variation of relative yields of H2 and HCN with changing of the coverage of azomethane. According to the calculations, desorption...
Boric acid/glycerol as an efficient catalyst for regioselective epoxide ring opening by aromatic amines in water, Article Green Chemistry Letters and Reviews ; Volume 5, Issue 1 , 2012 , Pages 1-5 ; 17518253 (ISSN) ; Gholami, H ; Saidi, M. R ; Sharif University of Technology
Regioselective epoxides ring opening with aromatic amines using boric acid and glycerol in water as a green media have been investigated. Corresponding β-amino alcohols were obtained with excellent yields and considerable regioselectivity. High yields of the products and mild reaction conditions using green catalyst and water as a green solvent are some advantages of this procedure
Dithiocarbamate as an efficient intermediate for the synthesis of 2-amino-1,3,4-thiadiazoles in water, Article Tetrahedron Letters ; Volume 51, Issue 5 , February , 2010 , Pages 790-792 ; 00404039 (ISSN) ; Ziyaei Halimehjani, A ; Saidi, M. R ; Sharif University of Technology
A new and facile protocol for the synthesis of 2-amino-1,3,4-thiadiazoles in water is described. Reaction of acid hydrazides with easily prepared dithiocarbamates gives the corresponding thiadiazoles in moderate to excellent yields. 2-Amino-1,3,4-oxadiazoles were not observed as side products using this procedure
Highly efficient and catalyst-free synthesis of unsymmetrical thioureas under solvent-free conditions, Article Tetrahedron Letters ; Volume 50, Issue 1 , 2009 , Pages 32-34 ; 00404039 (ISSN) ; Pourshojaei, Y ; Saidi, M. R ; Sharif University of Technology
A highly efficient and simple synthesis of unsymmetrical thioureas is reported based on the reaction of readily synthesized dithiocarbamates with amines, without using any catalyst under solvent-free conditions. The short reaction time, high yields, and solvent-free conditions are advantages of this method. We did not observe the formation of any symmetric disubstituted thiourea, under these reaction conditions. © 2008 Elsevier Ltd. All rights reserved
Revealing mass transfer and hydrodynamic effects in a PRDC column by using the integration of extraction and separation for molybdenum and tungsten ions from aqueous solution, Article Chemical Papers ; Volume 74, Issue 12 , 2020 , Pages 4295-4313 ; Torkaman, R ; Torab Mostaedi, M ; Asadollahzadeh, M ; Sharif University of Technology
The present work is performed to assess the hydrodynamic parameters and mass transfer coefficients in a PRDC column for the chemical reaction systems. By considering the selective extraction of molybdenum from tungsten, the extraction parameters and synergistic enhancement factor were interpreted at the batch experiments. In the column experiments, the impacts of operating conditions such as the agitation rate, inlet solvent phase velocity as well as inlet aqueous phase velocity were studied on the drop behavior, overall mass transfer coefficients, and extraction efficiencies. The modified correlations by using relationship of dimensionless numbers were illustrated to estimate the...
Article Tetrahedron Letters ; Volume 49, Issue 47 , 2008 , Pages 6682-6684 ; 00404039 (ISSN) ; Akbari, E ; Khejeh Amiri, A ; Saidi, M. R ; Sharif University of Technology
An efficient and highly chemoselective synthesis of symmetrical secondary amines via reductive amination of aldehydes with inexpensive and commercially available HMDS and sodium borohydride in high to quantitative yields is reported. © 2008 Elsevier Ltd. All rights reserved
A simple and novel eco-friendly process for the one-pot synthesis of dithiocarbamates from amines, carbon disulfide, and epoxides, Article Synlett ; Issue 8 , 2007 , Pages 1239-1242 ; 09365214 (ISSN) ; Pourhasan, B ; Aryanasab, F ; Saidi, M. R ; Sharif University of Technology
An environmentally benign, highly efficient, and simple protocol for the synthesis of various structurally divergent dithiocarbamate derivatives in one-pot reaction of amines, carbon disulfide, and epoxides, without using any solvent and catalyst at room temperature, is presented. This new procedure has the advantages of higher yield, lower cost, reduced environmental impact, and simple work-up procedure. © Georg Thieme Verlag Stuttgart
Article Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers ; Volume 45, Issue 2 A , 2006 , Pages 742-751 ; 00214922 (ISSN) ; Akhavan, M ; Sharif University of Technology
Single-phase Tm(Ba2-xPrx)Cu3O 7+δ and Lu(Ba2-xPrx)Cu3O 7+δ compounds with Pr content 0.0 ≤ x ≤ 1.0 have been prepared by solid-state reaction technique. The oxygen content of our samples is more than 7. X-ray diffraction (XRD) patterns demonstrate an orthorhombic to tetragonal transition with an increase in Pr content in both systems. For each system, a solubility limit exists for substitution of Pr at the Ba site. The intergrain region investigated by the thermally activated flux creep (TAFC) and Ambegaokar-Halperin (AH) models, show that the pinning energy decreases with increasing Pr content; it also decreases in each sample with increasing magnetic field as a power-law relation. The...
Simulation of Surface Chemical Reactions in Bosch Process for a Polymer Film and Investigation of Etching Quality, M.Sc. Thesis Sharif University of Technology ; Saeedi, Mohammad Saeed
Deep reactive ion etching is one of the most used techniques for manufacturing micro-structures. The most popular silicon DRIE technique is Bosch process. Ability to manufacture high aspect ratio features made Bosch process the main technique for developing micro-electromechanical devices. Dry etching is a combination of physical and chemical processes. The chemical processes play a very important role due to their speed of material removing and also due to their high selectivity. Also chemical processes are responsible for development of passive resist layer on the surface. On the other hand, if not controlled properly it can reduce anisotropy, resulting in a low quality etch. In this...
Reactive extraction of zinc ions in the Scheibel column; A case study by applying the mathematical modelling of mass transfer with forward mixing, Article Chemical Engineering and Processing - Process Intensification ; Volume 169 , 2021 ; 02552701 (ISSN) ; Torkaman, R ; Saremi, M ; Torab Mostaedi, M ; Asadollahzadeh, M ; Sharif University of Technology
Elsevier B.V 2021
An experimental and modeling study on the feasibility of the Scheibel extraction column is presented for heavy metal separation from chloride solution. In continuous experiments, the chemical reaction systems are considered zinc extraction by D2EHPA and stripping from the loaded organic phase by chloride solutions. The experimental results represent that the best extraction and stripping rates in the agitation speed of 155 rpm and the rate of inlet phases of 28 L/h are equal to 99.56% and 98.11%, respectively. The mass transfer modeling by applying the forward mixing is interpreted for solvent extraction systems in this column with the fitting technique. The calculated results from...
A facile aerobic copper-catalyzed α-oxygenation of aryl thioacetamides: An efficient access to α-keto aryl thioamides, Article Synlett ; Issue 6 , 2008 , Pages 892-896 ; 09365214 (ISSN) ; Mirjafary, Z ; Saeidian, H ; Jebeli Javan, M ; Sharif University of Technology
Copper(II) efficiently catalyzes the aerobic oxidation of aryl thioacetamides into the corresponding α-keto aryl thioamides in moderate to high yields in the presence of K2CO3 under O 2 atmosphere. This protocol is simple, clean, and generates water as the only byproduct. A mechanism is proposed for the reaction course. © Georg Thieme Verlag Stuttgart
Efficient method for oxidation of ketones to esters with 4-aminoperoxybenzoic acid supported on silica gel, Article Synthetic Communications ; Volume 38, Issue 12 , 2008 , Pages 2037-2042 ; 00397911 (ISSN) ; Hashemi, M. M ; Shahidi Zandi, M ; Sharif University of Technology
4-Aminoperoxybenzoic acid supported on silica gel was found to be a versatile and efficient oxidant for the oxidation of ketones to esters. Copyright © Taylor & Francis Group, LLC
Highly efficient ring opening reactions of epoxides with deactivated aromatic amines catalyzed by heteropoly acids in water, Article Tetrahedron ; Volume 63, Issue 4 , 2007 , Pages 888-891 ; 00404020 (ISSN) ; Saidi, M. R ; Sharif University of Technology
Heteropoly acid was found to be an effective and efficient catalyst for the ring opening reaction of epoxides with various aromatic amines to produce the corresponding β-amino alcohols in moderate to excellent yields in water. This method provides a new and efficient protocol in terms of mild reaction conditions, clean reaction profiles, small quantity of catalyst, and simple work-up procedure. © 2006
Synthesis and X-ray structural characterization of unsymmetrical tetradentate complexes of Ni(II) and Cu(II), Article Synthesis and Reactivity in Inorganic and Metal-Organic Chemistry ; Volume 32, Issue 2 , 2002 , Pages 345-355 ; 00945714 (ISSN) ; Boghaei, D. M ; Sharif University of Technology
The unsymmetrical tetradentate Schiff base H2L was prepared by the reaction of salicylaldehyde with the mono Schiff base derived from o-phenylenediamine and o-hydroxyacetophenone (HL1). NiL and CuL complexes were prepared and characterized by 1H NMR, IR and single crystal X-ray structure determination. Crystal data for NiL: triclinic space group P-1, a = 7.190 (2) Å, b = 13.059 (4) Å, c = 17.867 (10) Å, α = 74.888 (10)°, β = 84.206 (10)°, γ = 86.542 (2)° and z = 4. Crystal data for CuL: monoclinic space group P2I/n, a = 12.8209 (6) Å, b = 6.988 (3) Å, c = 18.601 (9) Å, β = 105.15° and z = 4. The Ni and Cu atoms have a slightly distorted square-planar coordination geometry
Mass transfer evaluation in a multi-impeller extractor for reactive Mo (VI) extraction from aqueous Sulphate solution by utilizing coupling of acid and solvating Extractants, Article Heat and Mass Transfer/Waerme- und Stoffuebertragung ; Volume 56, Issue 6 , 2020 , Pages 1995-2006 ; Torab Mostaedi, M ; Outokesh, M ; Asadollahzadeh, M ; Sharif University of Technology
In this study, mass transfer experimental data from the present column with 70 cm active column length and 11.3 cm internal diameter were interpreted for molybdenum extraction with a mixture of D2EHPA and TBP in terms of the axial diffusion model. The influence of extractants concentration and the initial aqueous pH have studied in the bench-scale experiments. The experimental finding demonstrated that the synergistic solvent extraction increases the constancy of the extracted complexes for transfer into the organic phase. The effect of operating parameters, including agitation speed and inlet phase velocities on the overall mass transfer coefficients under the chemical reaction system, is...
M.Sc. Thesis Sharif University of Technology ; Sadighi Bonabi, Rasul
Using field assisted dissociation model and with a classic view the dissociation probability is calculated when it a molecule is exposed with a Ti:sapphire laser with wavenumber of 800nm and the energy of . using gradient optimization method we find a tailored two rectangular laser pulse for controlling the dissociation of C-H bond of . Using classical method reduced the complicacy of solving schrodinger equation. In our optimization method in contrast with the usual controlling method experimental data is not needed and this reduced the controlling costs.
M.Sc. Thesis Sharif University of Technology ; Razvan, Mohammad Reza
In modeling of biological systems and chemical reaction networks, analy-sis the existence of multiple equilibria is important. Our interest in using dynamical system in such analyses comes from biology. So, we will study the qualitative properties of a dynamical system, described by a system of ordinary differential equations. In this thesis we will discuss the question of how to decide when a general chemical reaction system is incapable of admitting multiple euilibria, regardless of parameter values such as reaction rate constants. We will relate different graphs to chemical reaction systems, and by means of its paths and circuits, we will introduce some sufﬁcient conditions for...
M.Sc. Thesis Sharif University of Technology ; Shojaei, Akbar
Polydimethylsiloxane (PDMS) is one of the most important organosilicon elastomers. This polymer has a wide application such as medical engineering due to the unique characteristics, variety and ease of manufacture. Nowadays, the use of nanoparticles such as carbon nanotubes for improving the properties of elastomers is highly regarded owing to the fact that the improvement of properties such as mechanical properties broadens the applications of PDMS. Diamond nanoparticles has been the focus of numerous researchers in the past decade. In fact, nanodiamond has a good mechanical abrasion and thermal properties. In addition, the investigations proved that the nanoparticle is valuable in terms of...
M.Sc. Thesis Sharif University of Technology ; Davami, Parviz ; Halali, Mohammad
In this study, the recovery mechanism of nickel oxide by carbon dissolved in molten iron with the study of reaction kinetics were investigated. Nickel oxide pellets into molten iron containing graphite were added in the neutral atmosphere and the release of CO gas as a function of reaction time was measured until the end. The volume of gas produced at different times shows the number of moles of Ni metal was revived. Reaction by a) the following decomposition reaction under 1475 °C ; and b) carbon diffusion rate at temperatures over ° C1475 is controlled. The main reaction mechanism in order to a) decomposition of NiO; b) penetration of oxygen atoms in the melt, and c) reaction between...
Pyridinium salts - Versatile reagents for the regioselective synthesis of functionalized thiazocino[2,3-b]indoles by tandem dinucleophilic reactions of thiooxindoles, Article Tetrahedron ; Volume 68, Issue 47 , 2012 , Pages 9685-9693 ; 00404020 (ISSN) ; Moghaddam, F. M ; Gormay, P. V ; Semeniuchenko, V ; Villinger, A ; Langer, P ; Iaroshenko, V. O ; Sharif University of Technology
The reaction of thiooxindoles with various 2- and 3-substituted pyridinium salts afforded a variety of functionalized thiazocinoindoles. The products have been prepared in good to excellent yields by regioselective dinucleophilic C/S-cyclocondensation of thiooxindoles with pyridinium salts