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Issue Info: 
  • Year: 

    2013
  • Volume: 

    16
Measures: 
  • Views: 

    134
  • Downloads: 

    49
Keywords: 
Abstract: 

A HYDROGEN BOND IS THE ELECTROMAGNETIC ATTRACTIVE INTERACTION BETWEEN POLAR MOLECULES IN WHICH HYDROGEN (H) IS BOUND TO A HIGHLY ELECTRONEGATIVE ATOM. THESE HYDROGEN-BOND ATTRACTIONS CAN OCCUR WITHIN DIFFERENT PARTS OF A SINGLE MOLECULE (INTRAMOLECULAR HYDROGEN BONDING). INTRAMOLECULAR HYDROGEN BONDING CAN BE RESPONSIBLE FOR INCREASING ACIDITY AND Basicity IN ALCOHOLS WITH SEVERAL HYDROXYL GROUP AND AMINES WITH SEVERAL AMINO GROUPS ALSO AMINO ALCOHOLS.ALKANOLAMINES ARE CHEMICAL COMPOUNDS THAT CARRY HYDROXY (-OH) AND AMINO (-NH2, -NHR, AND -NR2) FUNCTIONAL GROUPS ON AN ALKANE BACKBONE. THE CO-EXISTENCE OF HYDROXY AND AMINE GROUPS IN ONE MOLECULE IS VERY COMMON IN MEDICATIONS AND BIOCHEMICALS. AMINO ALCOHOL DERIVATIVES HAVE BEEN EMPLOYED AS CATALYSTS AS WELL AS COUPLING PARTNERS IN THE SYNTHESIS OF MANY COMPOUNDS. THESE VERSATILE CHEMICALS ARE USED AS NEUTRALIZING AMINES FOR WATER TREATMENT, BIOLOGICAL BUFFERS, AND AS NEUTRALIZING AND BUFFERING CHEMICALS FOR PERSONAL CARE AND COSMETIC PRODUCTS.IN THIS WORK WE EXPLORED HYDROGEN BONDING EFFECT ON ACIDITY AND Basicity OF AMINO ALCOHOLS WITH SEVERAL HYDROXYL GROUP AND CALCULATED GAS PHASE ACIDITY, PKA AND PKB WITH GAUSSIAN 03 PROGRAM PACKAGE.

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Issue Info: 
  • Year: 

    2016
  • Volume: 

    19
Measures: 
  • Views: 

    161
  • Downloads: 

    61
Keywords: 
Abstract: 

THE EFFECTS OF SOLVENT–SOLUTE INTERACTIONS ON PHYSICOCHEMICAL PROPERTIES AND REACTIVITY PARAMETERS CAN BE STUDIED IN LINEAR SOLVATION ENERGY RELATIONSHIPS (LSERS). A LSER MODEL CONTAIN THREE SOLVENT’S WAS PROPOSED TO PREDICT AND DESCRIPT OSTWALD SOLUBILITY COEFFICIENT OF PYRENE WITH EMPIRICAL PROPERTIES OF VARIOUS ORGANIC SOLVENTS AND COVERED 0.88 AND 0.89 OF DATA VARIANCE IN TRAINING AND TEST SETS RESPECTIVELY. ...

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Author(s): 

Seyidova Fidan

Issue Info: 
  • Year: 

    2020
  • Volume: 

    17
  • Issue: 

    4
  • Pages: 

    85-93
Measures: 
  • Citations: 

    0
  • Views: 

    27
  • Downloads: 

    2
Abstract: 

In this work systems of sines $\sin \left(n+\beta \right)t,\, \, n=1,2, \ldots,$ and cosines $\cos \left(n-\beta \right)t,\, \, n=0,1,2, \ldots,$ are considered, where $\beta \in R-$is a real parameter. The subspace $M^{p,\alpha } \left(0,\pi \right)$ of the Morrey space $L^{p,\alpha } \left(0,\pi \right)$ in which continuous functions are dense is considered. Criterion   for the completeness, minimality and Basicity of these systems with respect to the parameter $\beta $  in the subspace  $M^{p,\alpha } \left(0,\pi \right)$, $1

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Issue Info: 
  • Year: 

    2006
  • Volume: 

    15
  • Issue: 

    11 (77)
  • Pages: 

    855-862
Measures: 
  • Citations: 

    0
  • Views: 

    683
  • Downloads: 

    779
Abstract: 

Epoxies are generally cross-linked by the addition of a hardener, most of the time a diamine such as diamine diphenyl sulphone, oxydianiline or methylene diamine, and then thermocured. These formulations are quite often used, particularly in the aerospace industry for making structural materials, prepregs or composites. In this paper we have investigated the cross-linking reactions of a difunctional cycloaliphatic epoxide monomer 3,4-epoxycyclohexylmethyl-3', 4'-epoxycyclohexane carboxylate initiated by UV-irradiation and compared the kinetics with N,N-diglycidyl- 4-glycidyloxyaniline (a nitrogen-containing monomer with a functionality of three) and 4,4'-methylenebis (N,N-diglycidylaniline) (another nitrogen-containing monomer with a functionality of four). Kinetics is followed using a differential photocalorimetry (DPC) technique. Upon UV irradiation in the presence of cationic photoinitiator, the difunctional cycloaliphatic epoxide monomer shows an exotherm peak whereas for the latter two monomers, no exotherm peaks were observed from the sample as a result of exposure to the UV source. To explain the phenomenon observed, the effect of addition of two amines with wide difference in the Basicity of p-nitroaniline and pyridine, has been studied on the UV-curing of epoxy resins. It has been found that the presence of amines does retard the rate of photopolymerization and the extent of retardation is dependent on the Basicity of the amine. Of the two amines used, pyridine and p-nitroaniline, the former is a stronger inhibitor, because of the ready availability of the lone pair of electrons. The results explain the non-reactivity of nitrogencontaining epoxy monomers N,N-diglycidyl-4-glycidyloxyaniline and 4,4'-methylenebis (N,N-diglycidylaniline) to cationic polymerization upon exposure to UV-radiation.

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Author(s): 

Journal: 

ACS Omega

Issue Info: 
  • Year: 

    2019
  • Volume: 

    4
  • Issue: 

    2
  • Pages: 

    2883-2892
Measures: 
  • Citations: 

    1
  • Views: 

    54
  • Downloads: 

    0
Keywords: 
Abstract: 

Yearly Impact: مرکز اطلاعات علمی Scientific Information Database (SID) - Trusted Source for Research and Academic Resources

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Issue Info: 
  • Year: 

    2018
  • Volume: 

    37
  • Issue: 

    2
  • Pages: 

    53-60
Measures: 
  • Citations: 

    0
  • Views: 

    275
  • Downloads: 

    227
Abstract: 

Two approaches for metal ion incorporation were employed to introduce Ca2+into SBA-15; Direct Synthesis (DS) and Wet Impregnation (WI). The non-ionic template was removed by two different methods; calcination and solvent extraction. The obtained catalysts were characterized by means of X-Ray Powder Diffraction (XRD), Energy Dispersive X-ray (EDX), and FT-IR spectroscopy. The Basicity was determined by using Hammett indicators and benzoic acid titration. The effects of synthesis methods and organic template on Basicity and catalytic performance were studied in the transesterification of Canola oil with methanol.1H NMR was used to analyze the products. The best results were obtained using catalysts which prepared by wet impregnation method. Furthermore calcination is a better method of template removal. So calcined Ca/SBA-15 prepared by impregnation showed particularly the highest activity (conversion 84.2 %).Although this catalyst has a limited reusability in transesterification reaction.

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Issue Info: 
  • Year: 

    2018
  • Volume: 

    8
  • Issue: 

    3
  • Pages: 

    321-331
Measures: 
  • Citations: 

    0
  • Views: 

    436
  • Downloads: 

    172
Abstract: 

In the present study, the effect of calcination temperature on the structure and performance of mesoporous CaO/TiO2– ZrO2 catalyst fabricated by sol– gel method used in the esterification reaction was assessed. Then, CaO/TiO2 catalyst was also synthesized via the same method to evaluate the effect of zirconia cations on its properties and activity. The samples were characterized by X-ray Diffraction (XRD), Fourier transmittance infra-red (FT-IR), Brunauer– Emmett– Teller (BET)– Barrett-Joyner-Halenda (BJH), scanning electron microscope (SEM) and transmission electron microscopy (TEM) analyses. Moreover, Hammett indicator method was utilized to assess the acidity and Basicity of the samples. It was found that zirconium was clearly incorporated in CaO/TiO2 lattice and transformed that from amorphous phase to crystalline structure. In addition, the Basicity and acidity of CaO/TiO2 was clearly increased by zirconia loading. Evaluation of the samples’ activity presented that CaO/TiO2 catalyst exhibit no activity in the esterification reaction, while all CaO/TiO2– ZrO2 catalysts showed high ability to convert oleic acid to its ester. Moreover, the catalyst calcined at 400 ° C showed the highest activity in the esterification reaction with desirable properties such as high crystallinity, acidity, Basicity and surface area along with well-distribution of particle size and pore size. The best catalyst converted around 90% of oleic acid to ester at optimized conditions of 150 ° C, 12: 1 molar ratio of methanol/oleic acid, 3 wt% of catalyst for 4 h of reaction time. Moreover, the sample was successfully used for five runs without significant reduction in activity that makes it a suitable choice as a catalyst for industrial applications.

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Author(s): 

MILANI J.M. | SAEID T.

Issue Info: 
  • Year: 

    2019
  • Volume: 

    5
  • Issue: 

    1
  • Pages: 

    77-91
Measures: 
  • Citations: 

    0
  • Views: 

    543
  • Downloads: 

    0
Abstract: 

In the present study, effect of inclusions characteristics changing on the formation of acicular ferritein submerged arc welding of API5l-X65 low alloy steel was investigated. Three different welding fluxes with different chemical composition and Basicity index of 0. 72, 0. 82 and 0. 99, and two different welding heat inputs of 1. 6 kJ / mm and 2. 4 kJ / mm were used to create inclusions with different characteristics such as chemical composition and size. The results indicate that inclusions acting as acicular ferrite nucleation sites and improvement of the microstructure and resulted mechanical properties, can be observed in welding conditions in which the welding flux with lowest Basicity index and higher welding heat input. Under these conditions, the percentage of inclusions with a high titanium oxide value and size range of 0. 5 to 1. 5 micrometers is increased, which increases the amount of acicular ferrite in the microstructure. However, in other welding conditions, formation of grain boundary ferrite reduces amount of acicular ferrite and weakens mechanical properties of weld metal compared to the base metal.

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Issue Info: 
  • Year: 

    2018
  • Volume: 

    13
  • Issue: 

    48
  • Pages: 

    311-324
Measures: 
  • Citations: 

    0
  • Views: 

    447
  • Downloads: 

    0
Abstract: 

Sulfonamides are a class of pharmaceutical compounds included – SO2NH– group that show a variety of biological activities. Sulfacetamide is an N-acyl sulfonamide that has broad-spectrum antibiotic effects. The acid-base properties of these compounds are believed to play an important role in their biological activities. Therefore, calculation of its acidic-Basicity has a specific importance in predicting and justifying the pharmaceutical properties of this compound. In this study, the synthesis of sulfacetamide has been carried out from a new multi-steps method in presence of heterogeneous catalyst of nano zinc oxide and homogeneous base catalyst of magnesium hydroxide. The stage and overall yields are better and their reaction time is less than previous procedures. Using heterogeneous catalyst, recoverable nano zinc oxide and magnesium hydroxide in solvent-free condition is a new procedure for better synthesis of this compound. Also in this work, acidic-Basicity of sulfacetamide and its derivatives have been studied using high level ab initio calculations. The calculated values have been found in good agreement with experimental data. Therefore, predictions of pharmaceutical properties of these compounds are possible.

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Issue Info: 
  • Year: 

    2012
  • Volume: 

    10
Measures: 
  • Views: 

    145
  • Downloads: 

    59
Keywords: 
Abstract: 

ELECTROCHEMICAL OXIDATION OF DOPAMINE HAS BEEN STUDIED IN THE PRESENCE OF VARIOUS AROMATIC AMINES WITH ELECTRON DONATING AND WITHDRAWING SUBSTITUENT. SOME ELECTROCHEMICAL TECHNIQUES SUCH AS CYCLIC VOLTAMMETRY AND ITS DIAGNOSTIC CRITERIA FOR VARIOUS ELECTRODE WERE USED. THE COMPETITION BETWEEN INTRAMOLECULAR AND INTERMOLECULAR MICHAEL ADDITION REACTION WERE STUDIED AT VARIOUS PH VALUES, VARIOUS ANILINE DERIVATIVES (ANILINE, 4-METHYLANILINE, 4-AMINOBENZOIC ACID, AND 4- NITROANILINE). THE RESULTS SHOW THAT DESPITE OF PRESENCE OF AMINE GROUP ON DOPAMINE AND POSSIBILITY OF INTRAMOLECULAR MICHAEL ADDITION, THE NUCLEOPHILIC ADDITION OF AROMATIC AMINES ARE THE DOMINANT REACTION AT MILD ACIDIC CONDITIONS. THIS IS RELATED TO LOWER Basicity OF ANILINE DERIVATIVE AND THEIR DEPROTONATION AT MILD ACIDIC CONDITIONS. THE AMINES WITH ELECTRON WITHDRAWING CHARACTER HAS LESS REACTIVITY AND RATE CONSTANT, BUT THEY SHOWS A GOOD REACTIVITY AT MORE ACIDIC CONDITIONS CONSIDERING THEIR LESS Basicity. ALSO THE SCHEME FOR THE ELECTROCHEMICAL OXIDATION OF DOPAMINE IN THE PRESENCE OF ANILINE DERIVATIVES IS PROPOSED AND TESTED BY DIGITAL SIMULATION. BASED ON AN ECE MECHANISM, THE OBSERVED HOMOGENEOUS RATE CONSTANTS (KOBS) OF MICHAEL ADDITION REACTION HAVE BEEN ESTIMATED BY COMPARISON OF THE SIMULATION RESULTS WITH EXPERIMENTAL CYCLIC VOLTAMMOGRAMS AT VARIOUS PHS. THE SIMULATED CYCLIC VOLTAMMOGRAMS SHOW GOOD AGREEMENT WITH THOSE OBTAINED EXPERIMENTALLY.

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