scholarly journals The Importance of Reaction Conditions on the Chemical Structure of N,O-Acylated Chitosan Derivatives

Molecules ◽  
2019 ◽  
Vol 24 (17) ◽  
pp. 3047 ◽  
Author(s):  
Agnieszka Piegat ◽  
Agata Goszczyńska ◽  
Tomasz Idzik ◽  
Agata Niemczyk
Keyword(s):  
Self Assembly ◽  
Chemical Structure ◽  
Resonance Spectroscopy ◽  
Reaction Conditions ◽  
Chitosan Derivatives ◽  
Synthesis Conditions ◽  
Carbodiimide Hydrochloride ◽  
Selective Acylation ◽  
Reaction Media ◽  
Acylation Reactions

The structure of acylated chitosan derivatives strongly determines the properties of obtained products, influencing their hydrodynamic properties and thereby their solubility or self-assembly susceptibility. In the present work, the significance of slight changes in acylation conditions on the structure and properties of the products is discussed. A series of chitosan-acylated derivatives was synthesized by varying reaction conditions in a two-step process. As reaction media, two diluted acid solutions—i.e., acetic acid and hydrochloric acid)—and two coupling systems—i.e., 1-ethyl-3-(3-dimethyl-aminopropyl)-1-carbodiimide hydrochloride (EDC) and N–hydroxysulfosuccinimide (EDC/NHS)—were used. The chemical structure of the derivatives was studied in detail by means of two spectroscopic methods, namely infrared and nuclear magnetic resonance spectroscopy, in order to analyze the preference of the systems towards N- or O-acylation reactions, depending on the synthesis conditions used. The results obtained from advanced 1H-13C HMQC spectra emphasized the challenge of achieving a selective acylation reaction path. Additionally, the study of the molecular weight and solution behavior of the derivatives revealed that even slight changes in their chemical structure have an important influence on their final properties. Therefore, an exact knowledge of the obtained structure of derivatives is essential to achieve reaction reproducibility and to target the application.

1H-NMR Analysis of Degree of Substitution in N,O-Carboxymethyl Chitosans from Various Chitosan Sources and Types

2012 ◽  
Vol 506 ◽  
pp. 158-161 ◽  
Author(s):  
A. Jaidee ◽  
Pornchai Rachtanapun ◽  
S. Luangkamin
Keyword(s):  
Chemical Structure ◽  
Carboxymethyl Chitosan ◽  
Degree Of Substitution ◽  
Resonance Spectroscopy ◽  
Nmr Analysis ◽  
Reaction Conditions ◽  
H Nmr ◽  
Fourier Transformed Infrared Spectroscopy ◽  
Chitosan Oligomer ◽  
Ft Ir

N,O-Carboxymethyl chitosans were synthesized by the reaction between shrimp, crab and squid chitosans with monochloroacetic acid under basic conditions at 50°C. The mole ratio of reactants was obtained from various reaction conditions of shrimp chitosan polymer and oligomer types. The mole ratio 1:12:6 of chitosan:sodium hydroxide:monochloroacetic acid was used for preparing carboxymethyl of chitosan polymer types while carboxymethyl of chitosan oligomer types were used the mole ratio 1:6:3 of chitosan:sodium hydroxide:monochloroacetic acid. The chemical structure was analyzed by fourier transformed infrared spectroscopy (FT-IR) and proton nuclear magnatic resonance spectroscopy (1H-NMR). The FT-IR was used for confirm the insertion of carboxymethyl group on chitosan molecules. The 1H-NMR was used for determining the degree of substitution (DS) of carboxymethylation at hydroxyl and amino sites of chitosans. Carboxymethyl chitosan samples had the total DS of carboxymethylation ranging from 1.0-2.2. The highest of DS of carboxymethylation was from shrimp chitosan oligomer type.

Developments in Colloidal Synthesis of Cu2-xS (0 ≤ x ≤ 1) Nanocrystals—An Overview

2020 ◽  
Vol 20 (6) ◽  
pp. 3659-3682
Author(s):  
Ananthakumar Soosaimanickam ◽  
Moorthy Babu Sridharan
Keyword(s):  
Energy Harvesting ◽  
Self Assembly ◽  
Colloidal Synthesis ◽  
Localized Surface Plasmon ◽  
Physical Parameters ◽  
Reaction Conditions ◽  
Synthesis Conditions ◽  
Solar Energy Harvesting ◽  
Colloidal Method

Colloidal synthesis of Cu2-xS (x = 0 ≤ x ≤ 1) nanocrystals (NCs) has been developed in recent years as broad context and its applications for energy harvesting is widely analyzed. Exciting properties of Cu2-xS NCs such as cation exchange, localized surface plasmon resonance (LSPR) in near infra-red (NIR) region are well manipulated by altering the stoichiometry through facile colloidal method. Due to their size, shape, phase tunability and self-assembly nature, synthesis of Cu2-xS NCs through colloidal medium has many advantages. Desired phase with desired composition can be achieved through facile tuning of solvent atmosphere and physical parameters of the synthesis conditions. In this regard, the present review summarizes recent achievements made in the colloidal synthesis of Cu2-xS NCs. Their structural and phase transformation in presence of different solvents and reaction conditions have been reviewed. The crucial role of phosphine-free solvents in synthesizing various phases, morphology of Cu2-xS NCs has been discussed. Applications of these Cu2-xS NCs for solar energy harvesting in third generation solar cells have also been reviewed.

Dimensionally-Controlled Hydrothermal Tm3+-doped Oxidic Nanocrystals and Their Photoluminescence Properties

2010 ◽  
Vol 1247 ◽  
Author(s):  
Rocío Calderón-Villajos ◽  
Carlos Zaldo ◽  
Concepción Cascales
Keyword(s):  
Single Crystals ◽  
Fluorescence Lifetimes ◽  
Photoluminescence Properties ◽  
Reaction Conditions ◽  
Hydrothermal Processes ◽  
Bulk Single Crystals ◽  
Template Free ◽  
Reaction Media

AbstractControlled reaction conditions in simple, template-free hydrothermal processes yield Tm-Lu2O3 and Tm-GdVO4 nanocrystals with well-defined specific morphologies and sizes. In both oxide families, nanocrystals prepared at pH 7 reaction media exhibit photoluminescence in ∼1.95 μm similar to bulk single crystals. For the lowest Tm3+ concentration (0.2 % mol) in GdVO4 measured 3H4 and 3F4 fluorescence lifetimes τ are very near to τrad.

Naturally Occurring Organic Acid-catalyzed Facile Diastereoselective Synthesis of Biologically Active (E)-3-(arylimino)indolin-2-one Derivatives in Water at Room Temperature

2019 ◽  
Vol 23 (16) ◽  
pp. 1778-1788 ◽  
Author(s):  
Gurpreet Kaur ◽  
Arvind Singh ◽  
Kiran Bala ◽  
Mamta Devi ◽  
Anjana Kumari ◽  
...  
Keyword(s):  
Room Temperature ◽  
Biologically Active ◽  
Environmentally Benign ◽  
Diastereoselective Synthesis ◽  
Substituted Anilines ◽  
Reaction Conditions ◽  
Naturally Occurring ◽  
Acid Catalyzed ◽  
Reaction Media ◽  
Column Chromatographic

A simple, straightforward and efficient method has been developed for the synthesis of (E)-3-(arylimino)indolin-2-one derivatives and (E)-2-((4-methoxyphenyl)imino)- acenaphthylen-1(2H)-one. The synthesis of these biologically-significant scaffolds was achieved from the reactions of various substituted anilines and isatins or acenaphthaquinone, respectively, using commercially available, environmentally benign and naturally occurring organic acids such as mandelic acid or itaconic acid as catalyst in aqueous medium at room temperature. Mild reaction conditions, energy efficiency, good to excellent yields, environmentally benign conditions, easy isolation of products, no need of column chromatographic separation and the reusability of reaction media are some of the significant features of the present protocol.

scholarly journals Self-Assembled Bimetallic Aluminum-Salen Catalyst for the Cyclic Carbonates Synthesis

Molecules ◽  
2021 ◽  
Vol 26 (13) ◽  
pp. 4097
Author(s):  
Wooyong Seong ◽  
Hyungwoo Hahm ◽  
Seyong Kim ◽  
Jongwoo Park ◽  
Khalil A. Abboud ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Self Assembly ◽  
Reaction Pathway ◽  
Kinetic Studies ◽  
Cyclic Carbonate ◽  
Reaction Conditions ◽  
Formation Reaction ◽  
X Ray ◽  
Carbonate Formation ◽  
Salen Aluminum

Bimetallic bis-urea functionalized salen-aluminum catalysts have been developed for cyclic carbonate synthesis from epoxides and CO2. The urea moiety provides a bimetallic scaffold through hydrogen bonding, which expedites the cyclic carbonate formation reaction under mild reaction conditions. The turnover frequency (TOF) of the bis-urea salen Al catalyst is three times higher than that of a μ-oxo-bridged catalyst, and 13 times higher than that of a monomeric salen aluminum catalyst. The bimetallic reaction pathway is suggested based on urea additive studies and kinetic studies. Additionally, the X-ray crystal structure of a bis-urea salen Ni complex supports the self-assembly of the bis-urea salen metal complex through hydrogen bonding.

scholarly journals Catalytic Activity of High-Surface-Area Amorphous MgO Obtained from Upsalite

Catalysts ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1338
Author(s):  
Marek Gliński ◽  
Ewa M. Iwanek (nee Wilczkowska) ◽  
Urszula Ulkowska ◽  
Agnieszka Czajka ◽  
Zbigniew Kaszkur
Keyword(s):  
Surface Area ◽  
Carbonyl Compounds ◽  
Main Product ◽  
High Surface ◽  
High Surface Area ◽  
Hydrogenation Reaction ◽  
Transfer Hydrogenation ◽  
Reaction Conditions ◽  
Synthesis Conditions ◽  
Transfer Hydrogenation Reaction

The first aim of the research was to synthesize a pure Upsalite, which is an amorphous form of MgCO3, by modifying a procedure described in the literature, so that it would be the precursor of a high-surface, amorphous magnesium oxide. The results indicate that within the studied reaction conditions, the type of alcohol used as the reactant has the most pronounced effect on the yield of reaction. From the two alcohols that led to the highest yield of Upsalite, methanol gave a substantially larger surface area (794 vs. 191 m2 g−1). The optimized synthesis conditions of Upsalite were used to obtain MgO via thermolysis, whose activity in the transfer hydrogenation reaction (THR) from ethanol, 2-propanol and 2-pentanol to various carbonyl compounds was determined. The optimal conditions for the thermolysis were as follows: vacuum, T = 673 K as the final temperature, and a heating rate of 2 deg min−1. The high-surface, amorphous magnesia (SBET = 488 m2 g−1) was found to be a very selective catalyst to 4-t-butylcyclohexanone in THR, which led to a diastereoselectivity of over 94% to the E-isomer of 4-t-butylcyclohexanol for more than 3 h, with conversions of up to 97% with either 2-propanol or 2-pentanol as the hydrogen donor. In the case of acrolein and 2-n-propylacrolein being used as the hydrogen acceptors, the unsaturated alcohol (UOL) was the main product of the reaction, with higher UOL yields noted for ethanol than 2-propanol.

Study on Synthesis of Cyclotriphosphazene Containing Aminopropylsilicone Functional Group as Flame Retardant

2013 ◽  
Vol 683 ◽  
pp. 25-29 ◽  
Author(s):  
Lan Lan He ◽  
Yi Zhang ◽  
Zhao Lu Qin ◽  
Yan Hua Lan ◽  
Ding Hua Li ◽  
...  
Keyword(s):  
Flame Retardant ◽  
Chemical Structure ◽  
Gel Permeation Chromatography ◽  
Molar Ratio ◽  
Reaction Conditions ◽  
Element Analysis ◽  
Fourier Transformed Infrared Spectroscopy ◽  
Industrial Grade ◽  
Distribution Calculation ◽  
Optimum Reaction

A novel non-halogen flame retardant APESP, cyclotriphosphazene containing six aminopropyltriethoxysilicone functional groups N3P3[NH(CH2)3Si(OCH2CH3)3]6, was synthesized by menas of SN2 nucleophilic substitution reaction, using hexachlorocyclotriphosphazene(HCCP) and 3-aminopropyltriethoxy-silane (KH550) as material. Firstly the industrial grade HCCP was purified through recrystallization and sublimation. Then the reaction process was investigated to prompt the yield, and the optimum reaction conditions were as follows: triethylamine as acid-binding agent, tetrahydrofuran as solvent, HCCP/KH550/triethylamine molar ratio 1:7.2:7.2, dripping time: 1 hour, temperature: 67°C and reaction time: 20h. Maximum APESP yield reached 94.3%. The chemical structure and purity was characterized by element analysis, Fourier-transformed infrared spectroscopy (FTIR), mass spectrum, gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR) analysis. The results showed that the structure of synthesized product is consistent with the theoretical structure, in which the chlorine atoms were completely substituted. The charge distribution calculation of HCCP and KH550 confirmed the reaction mechanism.

scholarly journals Self-Assembled Metal–Organic Biohybrids (MOBs) Using Copper and Silver for Cell Studies

Nanomaterials ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 1282 ◽  
Author(s):  
Neha Karekar ◽  
Anik Karan ◽  
Elnaz Khezerlou ◽  
Neela Prajapati ◽  
Chelsea D. Pernici ◽  
...  
Keyword(s):  
Self Assembly ◽  
Neuroblastoma Cells ◽  
The Novel ◽  
Culture Methods ◽  
Synthesis Conditions ◽  
Tissue Constructs ◽  
Silver Sulfate ◽  
Significant Toxicity ◽  
Metal Organic

The novel synthesis of metal-containing biohybrids using self-assembly methods at physiological temperatures (37 °C) was compared for copper and silver using the amino acid dimer cystine. Once assembled, the copper containing biohybrid is a stable, high-aspect ratio structure, which we call CuHARS. Using the same synthesis conditions, but replacing copper with silver, we have synthesized cystine-capped silver nanoparticles (AgCysNPs), which are shown here to form stable colloid solutions in contrast to the CuHARS, which settle out from a 1 mg/mL solution in 90 min. Both the copper and silver biohybrids, as synthesized, demonstrate very low agglomeration which we have applied for the purpose of applications with cell culture methods, namely, for testing as anti-cancer compounds. AgCysNPs (1000 ng/mL) demonstrated significant toxicity (only 6.8% viability) to glioma and neuroblastoma cells in vitro, with concentrations as low as 20 ng/mL causing some toxicity. In contrast, CuHARS required at least 5 μg/mL. For comparative purposes, silver sulfate at 100 ng/mL decreased viability by 52% and copper sulfate at 100 ng/mL only by 19.5% on glioma cells. Using these methods, the novel materials were tested here as metal–organic biohybrids (MOBs), and it is anticipated that the functionalization and dynamics of MOBs may result in building a foundation of new materials for cellular applications, including cell engineering of both normal and diseased cells and tissue constructs.

Preparation and characterization of a novel amphoteric polymer for oil well cementing with superior performances

2020 ◽  
Vol 29 (1) ◽  
pp. 29-39
Author(s):  
Tang Xin ◽  
Hu Xuzeng ◽  
Wan Haodong
Keyword(s):  
Thermal Stability ◽  
Orthogonal Experiment ◽  
Radical Copolymerization ◽  
Proton Nuclear Magnetic Resonance ◽  
Fluid Loss ◽  
Resonance Spectroscopy ◽  
Oil Well ◽  
Cement Slurry ◽  
Synthesis Conditions ◽  
Th 1

A novel amphoteric polymer TH-1 was synthesized using the monomers of 2-acrylamido-2-methylpropane sulfonic acid, acrylic acid, acrylamide, and cationic monomer through radical copolymerization as filtrate loss reducer in oil well cementing. Optimal synthesis conditions of TH-1 were obtained by an orthogonal experiment. The composition of copolymer (TH-1) was characterized by Fourier-transform infrared spectrum and proton nuclear magnetic resonance spectroscopy. The thermal stability of the synthesized copolymer was tested by thermogravimetric analysis. The fluid loss (FL) control and thickening performance of cement slurry incorporating TH-1 were evaluated at different temperatures. The filtration reduction mechanism of TH-1 was finally discussed. Results suggest that the amphoteric polymer is the target product polymerized by all the monomers, which presents excellent filtrate reduction property, high thermal stability, and strong saline tolerance under 200°C. The amphoteric polymer TH-1 includes cationic and anionic group in a molecule structure, which can adsorb firmly onto the surface of cement particles through electrostatic attraction and form adsorption membrane of viscoelastic polymer. In this way, compact cement filter cakes are formed, thereby efficiently reducing the FL.

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