Loading...
Search for:
salts
0.007 seconds
Total 195 records
Investigation of the reaction of dithiocarbamic acid salts with aromatic aldehydes
, Article Organic Letters ; Volume 14, Issue 15 , July , 2012 , Pages 3838-3841 ; 15237060 (ISSN) ; Hajiloo Shayegan, M ; Hashemi, M. M ; Notash, B ; Sharif University of Technology
ACS
2012
Abstract
A reaction of dithiocarbamic acid salts with carbonyl compounds was investigated for the first time in the presence of BF 3•OEt 2. The reaction is temperature dependent and gives gem-bis(dithiocarbamates) at 35-45 °C as a molecule with high equivalents of dithiocarbamate groups. At lower temperatures (15-20 °C), the 2-iminium-1,3-dithietane is obtained as the only product. The structure of a 2-iminium-1,3-dithietane was accomplished by X-ray crystallographic analysis
A new protocol for the preparation of aminals from aromatic aldehydes and their facile conversion to phosphonates
, Article Phosphorus, Sulfur and Silicon and the Related Elements ; Volume 179, Issue 1 , 2004 , Pages 89-96 ; 10426507 (ISSN) ; Saidi, M. R ; Sharif University of Technology
2004
Abstract
A new and fast method for the preparation of aminals is reported from the reaction of aromatic aldehydes and secondary amines in the presence of potassium carbonate in high yields. The aminal can be converted to the corresponding iminum salt in reaction with acetyl chloride very easily and in very short time with high yield. Addition of trialkylphosphite, as one possible nucleophile, to the prepared iminium salt produces the α-amino phosphonate in very high yield
Modified Chitosan. 3. Superabsorbency, Salt- and pH-Sensivity of Smart Ampholitic hydrogels from Chitosan-g-PAN [electronic resource]
, Article Polymers for Advanced Technologies ; Volume 15, Issue 4, pages 173–180, April 2004 ; Zohuriaan-Mehr, M. J ; Pourjavadi, M. J
Abstract
Polyacrylonitrile (PAN) grafted chitosan was prepared by ceric-initiated graft polymerization of acrylonitrile onto chitosan in a homogenous medium. The copolymer chitosan-g-PAN product was then hydrolyzed to yield a novel smart hydrogel (H-chitoPAN) with superabsorbing properties. The influence of add-on values as well as temperature and time of hydrolysis of the initial chitosan-g-PAN on swelling behavior of the hydrogel was evaluated in water and various salt solutions. The swelling kinetics of the superabsorbing hydrogel was studied as well. The hydrogels exhibited ampholytic and pH-sensitivity characteristics. Several sharp swelling changes were observed in lieu of pH variations in a...
Modified chitosan III, superabsorbency, salt- and pH-sensitivity of smart ampholytic hydrogels from chitosan-g-PAN
, Article Polymers for Advanced Technologies ; Volume 15, Issue 4 , 2004 , Pages 173-180 ; 10427147 (ISSN) ; Zohuriaan Mehr, M. J ; Pourjavadi, A ; Sharif University of Technology
John Wiley and Sons Ltd
2004
Abstract
Polyacrylonitrile (PAN) grafted chitosan was prepared by ceric-initiated graft polymerization of acrylonitrile onto chitosan in a homogenous medium. The copolymer chitosan-g-PAN product was then hydrolyzed to yield a novel smart hydrogel (H-chitoPAN) with superabsorbing properties. The influence of add-on values as well as temperature and time of hydrolysis of the initial chitosan-g-PAN on swelling behavior of the hydrogel was evaluated in water and various salt solutions. The swelling kinetics of the superabsorbing hydrogel was studied as well. The hydrogels exhibited ampholytic and pH-sensitivity characteristics. Several sharp swelling changes were observed in lieu of pH variations in a...
Efficient and green synthesis of new polycyclic procyanidin derivatives via tandem dinucleophilic addition of indolin-2-thiones to flavylium salts
, Article Pure and Applied Chemistry ; Volume 83, Issue 3 , January , 2011 , Pages 709-713 ; 00334545 (ISSN) ; Foroushani, B. K ; Saeidian, H ; Nourian, S ; Mirjafary, Z ; Kiamehr, M ; Sharif University of Technology
2011
Abstract
The green synthesis of a new series of polycyclic procyanidin derivatives has been achieved in good yields by tandem dinucleophilic addition of indolin-2-thiones to flavylium salts. The procedure is efficient and simple, and the substrates are easily available
Thermodynamic properties of aqueous glucose-urea-salt systems
, Article Journal of Solution Chemistry ; Volume 43, Issue 6 , June , 2014 , Pages 1110-1131 ; ISSN: 00959782 ; Held, C ; Ghotbi, C ; Abdekhodaie, M. J ; Sadowski, G ; Sharif University of Technology
Abstract
In this work, the thermodynamic behavior of aqueous solutions containing the solutes NaCl, glucose, and/or urea is investigated. These substances are vital components for living bodies and further they are main components of blood serum. Osmotic coefficients were determined by cryoscopic measurements in single-solute and multi-solute aqueous solutions containing salts (NaCl, KCl, CaCl2), glucose, and/or urea. The results show that NaCl determines the osmotic coefficients in the urea/glucose/NaCl/water system. Investigation of the effect of different salts on osmotic coefficients revealed ion-specific effects. At physiologically important solute concentrations in typical blood serum...
Microwave assisted preparation of flavylium salts with perchloric acid impregnated on silica gel under solvent-free conditions
, Article Letters in Organic Chemistry ; Vol. 11, issue. 10 , 2014 , pp. 713-718 ; ISSN: 15701786 ; Foroushani, B. K ; Ghonouei, N ; Kalahroodi, E. L ; Sharif University of Technology
Abstract
Perchloric acid immobilized on silica gel (SiO2-HClO4) has been utilized as a mild and cheap reagent for onepot preparation of different varieties of flavylium salts via tandem reaction of different acetophenones with Salicylaldehydes under solvent-free conditions. Different reaction conditions such as conventional heating and microwave irradiation have been investigated. The corresponding flavylium salts have been prepared in high yields. The procedure is milder and more convenient than the known procedures
Tandem dinucleophilic cyclization of cyclohexane-1,3-diones with pyridinium salts
, Article Beilstein Journal of Organic Chemistry ; Volume 9 , 2013 , Pages 1119-1126 ; 18605397 (ISSN) ; Moghaddam, F. M ; Mkrtchyan, S ; Semeniuchenko, V ; Supe, L ; Villinger, A ; Langer, P ; Laroshenko, V. O ; Sharif University of Technology
2013
Abstract
The cyclization of cyclohexane-1,3-diones with various substituted pyridinium salts afforded functionalized 8-oxa-10-aza-tricyclo[7.3.1.0 2,7]trideca-2(7),11-dienes. The reaction proceeds by regioselective attack of the central carbon atom of the 1,3-dicar-bonyl unit to 4-position of the pyridinium salt and subsequent cyclization by base-assisted proton migration and nucleophilic addition of the oxygen atom to the 2-position, as was elucidated by DFT computations. Fairly extensive screening of bases and additives revealed that the presence of potassium cations is essential for formation of the product
The synthesis of dibenzazocines via tandem dinucleophilic addition of phenols to quinolinium salts
, Article Arkivoc ; Volume 2010, Issue 11 , Sep , 2010 , Pages 91-100 ; 1551-7012 (ISSN) ; Saeidian, H ; Kiamehr, M ; Mirjafary, Z ; Taheri, S ; Sharif University of Technology
Arkat
2010
Abstract
Dibenzazocines were prepared via tandem dinucleophilic addition of phenols to quinolinium salts in good yields. The procedure is efficient, simple and the substrates are easily available
Modified chitosan 4. Superabsorbent hydrogels from poly(acrylic acid-co-acrylamide) grafted chitosan with salt- and pH-responsiveness properties
, Article European Polymer Journal ; Volume 40, Issue 7 , 2004 , Pages 1399-1407 ; 00143057 (ISSN) ; Pourjavadi, A ; Hosseinzadeh, H ; Zohuriaan, M. J ; Sharif University of Technology
2004
Abstract
Graft copolymerization of mixtures of acrylic acid (AA) and acrylamide (AAm) onto chitosan was carried out by using potassium persulfate (KPS) as a free radical initiator in the presence of methylenebisacrylamide (MBA) as a crosslinker. The effect of reaction variables, such as MBA concentration and AA/AAm ratio on the water absorbency capacity have been investigated. The polymer structures were confirmed by FTIR spectroscopy. Water absorbencies were compared for the hydrogels before and after alkaline hydrolysis. In the non-hydrolyzed hydrogel, enhanced water absorbency was obtained with increasing AA in monomer feed. However, after saponification, the sample with high AAm ratio exhibited...
Superabsorbent hydrogels from starch-g-PAN: Effect of some reaction variables on swelling behavior
, Article Journal of Polymer Materials ; Volume 20, Issue 1 , 2003 , Pages 113-120 ; 09700838 (ISSN) ; Pourjavadi, A ; Sharif University of Technology
2003
Abstract
Two series of alkali hydrolyzed starch-g-polyacrylonitrile (H-SPAN) superabsorbents were prepared from granular and gelatinized corn starches. The grafting parameters of SPAN copolymers were determined and the polymers were analyzed by FTIR spectroscopy. A combination of three influencing factors (i.e. thermal pre-treatment of the initial starch, presence or absence of oxygen in the stage of ceric-initiated PAN grafting, and neutralization after alkali treatment) on swelling characteristics of the final hydrogel was evaluated in a practical viewpoint. The superabsorbents were discriminated according to their swelling behavior in water and different aqueous salt solutions. The swelling...
A new protocol for the Baylis-Hillman reaction: The reaction of iminium salts prepared in situ with methyl acrylate
, Article Tetrahedron Letters ; Volume 43, Issue 24 , 2002 , Pages 4305-4308 ; 00404039 (ISSN) ; Saidi, M. R ; Sharif University of Technology
2002
Abstract
In situ prepared iminium salts are very effective electrophiles in Baylis-Hillman reactions and react with methyl acrylate in the presence of a catalytic amount of a tertiary amine at ambient temperatures to afford the corresponding Baylis-Hillman adducts. The product undergoes conjugated addition with (trimethylsilyl)dialkylamines to give the diamine 5 in good yields. © 2002 Elsevier Science Ltd. All rights reserved
Salt- and pH-resisting collagen-based highly porous hydrogel
, Article Polymer Journal ; Volume 40, Issue 2 , 2008 , Pages 94-103 ; 00323896 (ISSN) ; Kurdtabar, M ; Ghasemzadeh, H ; Sharif University of Technology
2008
Abstract
A novel approach was developed to prepare a highly porous hydrogel with superior salt- and pH-resisting properties. According to this method, synthetic comonomers, i.e. acrylic acid (AA) and 2-acrylamido-2-methylpropanesulfonic acid (AMPS), were polymerized and crosslinked in the presence of hydrolyzed collagen as a natural backbone. The characterizations of hydrogels were investigated by swelling experiment, Fourier transform infrared (FT-IR) spectroscopy, acid-base titration and thermogravimetric analysis (TGA). Morphology of the samples was examined by scanning electron microscopy (SEM). Experimental results indicate that the hydrogel has an absorbency of 360 and 73-82 g/g for distilled...
A facile synthesis of bridged polycyclic naphthooxazocine skeletons: Eight-membered-ring constructions via tandem dinucleophilic addition of naphthalenols to quinolinium salts
, Article Helvetica Chimica Acta ; Volume 94, Issue 1 , 2011 , Pages 142-147 ; 0018019X (ISSN) ; Taheri, S ; Mirjafary, Z ; Saeidian, H ; Kiamehr, M ; Tafazzoli, M ; Sharif University of Technology
2011
Abstract
The efficient synthesis of bridged polycyclic naphthooxazocines 3 via addition of naphthalenols 1 as a bis-nucleophile to N-alkylquinolinium salts 2 is described (Scheme 1 and Table 2). This new approach provides a powerful entry into polycyclic structures containing bicyclic N,O-acetals related to bioactive compounds
Molten salt synthesis of a SiC coating on graphite flakes for application in refractory castables
, Article Ceramics International ; 2016 ; 02728842 (ISSN) ; Bavand Vandchali, M ; Golestani Fard, F ; Nemati, A ; Sharif University of Technology
Elsevier Ltd
Abstract
A silicon carbide coating was formed on the surface of graphite flakes by reaction of molten Si with carbon at 1100-1300. °C in a 95%KCl-5%NaF molten salt under Ar atmosphere. The effect of temperature and Si/graphite ratio in the initial mixture on the quality and the amount of SiC were investigated by XRD and SEM/EDS analyses. Also, the water wettability, oxidation resistance and zeta potential of un-coated and coated graphite were examined by TGA analysis and sedimentation test. The results show the amount of coating to increase in the coated flakes with increasing temperature and Si/graphite ratio. The SiC coating improves water wettability of graphite and acts as a protective layer to...
Hot corrosion behavior and near-surface microstructure of a “low-temperature high-activity Cr-aluminide” coating on inconel 738LC exposed to Na2SO4, Na2SO4 + V2O5 and Na2SO4 + V2O5 + NaCl at 900 °C
, Article Corrosion Science ; Volume 128 , 2017 , Pages 42-53 ; 0010938X (ISSN) ; Ghasemi, B ; Sadrnezhaad, S. K ; Habibollahzadeh, A ; Jafarzadeh, K ; Sharif University of Technology
Abstract
Hot corrosion is a serious problem in gas turbines due to poor quality fuels which contain Na, V, S and Cl. To resolve the problem, Cr-aluminide was coated on IN-738LC superalloy with a two steps pack cementation process. Oxidation behavior and near-surface microstructure of the coating showed consecutive increase in destruction by exposition to Na2SO4, 75Na2SO4 + 25 V2O5 and 70Na2SO4 + 25 V2O5 + 5NaCl (wt.%). Kinetic studies indicated parabolic corrosion rate in salt-less samples due to diffusion. Similar expression for salt-covered samples was assessed for oxide dissolution. Plate-like, broken-plate-like and cauliflower-like morphologies attributed to the corrosion products were observed...
Salt and pepper noise removal for image signals
, Article 2008 International Conference on Telecommunications, ICT, St. Petersburg, 16 June 2008 through 19 June 2008 ; October , 2008 ; 9781424420360 (ISBN) ; Zahedpour, S ; Soltanolkotabi, M ; Amini, A ; Marvasti, F ; Sharif University of Technology
2008
Abstract
In this paper we propose a new method to recover images corrupted with salt and pepper noise. The proposed method uses ordered statistics filtering and soft-decisioning in successive approximations to find the locations and amplitudes of all the impulses. In our method we use soft-decision to generate a mask which is based on histogram distributions in local windows to distinguish impulsive noise from legitimate pixels. This mask is used to obtain an estimate of the original image by an iterative method. The result of the aforementioned algorithm can be fed back into the system to improve the image reconstruction process. This algorithm is analyzed and verified by simulation results....
Dispersivity, collapsibility and microstructure of a natural dispersive loess from Iran
, Article 16th Asian Regional Conference on Soil Mechanics and Geotechnical Engineering, ARC 2019, 14 October 2019 through 18 October 2019 ; 2020 ; Nasiri, H ; Panahi, P. A ; Sadeghi, M ; Sharif University of Technology
Asian Regional Conference on Soil Mechanics and Geotechnical Engineering
2020
Abstract
A new type of collapsible soil was encountered in Southern Iran and caused some serious technical problems including subsidence, collapse and sinkholes during the construction of Zahedan-Chabahar railway. Field observations indicated that in-situ soil contains excessive amount of salts resulting in dispersive features in response to seepage forces in addition to its collapsibility. Therefore, a systematic research plan including field sampling and laboratory testing was carried out to investigate the observed geotechnical features. Results of physio-chemical tests revealed the dominance of Sodium in excess of 70% relative to total dissolved salts, which results in high dispersive potential....
Multiple linear regression modeling of the critical micelle concentration of alkyltrimethylammonium and alkylpyridinium salts
, Article Journal of Surfactants and Detergents ; Volume 6, Issue 1 , 2003 , Pages 25-30 ; 10973958 (ISSN) ; Konouz, E ; Sharif University of Technology
American Oil Chemists Society
2003
Abstract
The critical micelle concentration (CMC) of a set of 30 alkyltrimethylammonium [RN+(R′)3X-] and alkylpyridinium salts [RN+φX-] was related to topological, electronic, and molecular structure parameters using a stepwise regression method. Among different models obtained, two equations were selected as the best and their specifications are given. The statistics for these models together with the crossvalidation results indicate the capability of both models to predict the CMC of cationic surfactants. The results obtained for alkyltrimethylammonium salts indicate that geometric characteristics such as volume of the tail of the molecule, maximum distance between the atoms, and surface area play...
, M.Sc. Thesis Sharif University of Technology ; Matloubi Moghaddam, Firouz (Supervisor)
Abstract
Stachys species have played crucial role as a folk-medicinal plants since so many years ago. According to their commercial interest in the production of essential oils and flavoring agents, investigation through their secondary metabolisms still has been done. In the first part of this research, we have done our phytochemical investigation of Stachys inflata. The aerial parts of this plant have been collected; we could isolate and identify 5 molecules. Their structural elucidation was accomplished by extensive spectroscopic methods including 1H NMR, 13C NMR and 13C Dept experiments. In the second part of the research, we have reported a new and efficient synthesis of a broad spectrum of...