Preparation and sorption properties of a β‐cyclodextrin‐linked chitosan derivative

β‐Cyclodextrin (β‐CD) was coupled to chitosan by the intermediate of its monochlorotriazinyl derivative, called βW7MCT, so that a chitosan derivative bearing cyclodextrin was obtained. Because the average degree of substitution of the cyclodextrin derivative was 2.8, the reaction yielded crosslinked insoluble products. The structure of these materials has been investigated by high‐resolution magic‐angle spinning (HRMAS) with gradients. For the first time, HRMAS spectra of chitosan polymers containing β‐CD were obtained. This NMR technique produced one‐ and two‐dimensional well‐resolved solid‐state spectra. These data confirm the proposed structure. Decontamination of waters containing textile dyes were carried out with the crosslinked derivatives. These tests showed that the new chitosan derivatives are characterized by a rate of sorption and a global efficiency superior to that of the parent chitosan polymer and of the well‐known cyclodextrin‐epichlorohydrin gels. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 39: 169–176, 2001     

Synthesis in a gel and sorption properties of N-2-sulfoethyl chitosan

A new procedure was developed for preparation of chelate amino-containing polymer N-2-sulfoethyl chitosan by synthesis in a gel through the reaction between chitosan and sodium 2-bromoethanesulfonate, yielding a polymer with the degree of substitution of up to 0.5. The structure of the resulting polymers was confirmed by ¹H NMR spectroscopy. The sorption characteristics with respect to transition and alkaline-earth metal ions were determined for the cross-linked polymers.     

Cyclization of mercaptopyrimidine derivative: a facile synthetic approach for condensed pyrimidines

Research on Chemical Intermediates - In the present study, we report the synthesis of different condensed pyrimidine derivatives by the exploitation of addition reactions to π-deficient...     

The green synthetic approach to prepare PbS/chitosan nanocomposites and its new optical sensing active properties for 2-isonaphthol

PbS nanoparticles were successfully synthesized in the presence of chitosan (CS) through an in situ method. This method is an effective, simple, and green synthetic approach to preparing nanomaterial films. The structure, morphology, and stability of the materials were examined via Fourier transform infrared spectroscopy, and the characteristic peak of the NH₂ group shifted from 1554 to 1598 cm^-1 after PbS was formed in the film. The Pb–S bond exhibited a vibrational absorption peak at 605 cm^-1, which further confirmed the generation of PbS nanoparticles. Differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) procedures were performed as well; well-defined nanoparticles were detected in the CS matrix by SEM. As per DSC findings, the thermal stabilities of the PbS/CS film were 50°C higher than those of pure CS. Moreover, the fluorescence emission of the films was sensitive to the presence of 2-isonaphthol. The effect of 2-isonaphthol concentration on the emission of films increases significantly with an increase in this concentration. The concentration-dependent fluorescence can be described by a correlation equation when 2-isonaphthol concentration ranges from 0 to 12.56 mg/L, and fluorescence results revealed that the PbS/CS nanoparticles were sensitive to 2-isonaphthol in the liquid phase. The proposed method may be applied to detect 2-isonaphthol in the environment and in the chemical industry.     

A new approach to preparation of granulated materials based on chitosan and its imidazole derivative

A new approach to preparation of granulated materials based on chitosan and N-(5-methyl-4-imidazolyl)- methyl chitosan was developed. The procedure is simple and efficient and involves the use of glutaraldehyde as cross-linking agent without using precipitants. The composition and structural features of the materials obtained were determined by elemental analysis and Fourier IR spectroscopy. The dependence of the degree of material swelling on the degree of functionalization with glutaraldehyde was determined. The polymer granules were used as support for Pd0-containing catalysts for reduction of organic compounds.     

Preparation of sorbents based on chitosan and its sulfoethyl derivative for sorption of perrhenate ions

The ability of cross-linked chitosan to take up perrhenate ions was studied systematically. The degree of sorption from acetate buffer solution at pH in the interval 2.8–3.1 reaches 85% and more. N-Sulfoethylation decreases the sorption ability of chitosan, but expands the pH interval of sorption and shifts the optimum pH value toward higher acidities. The sorption materials exhibit higher sorption rate than standard synthetic ion exchangers do. The data obtained suggest predominant ion-exchange mechanism of sorption of perrhenate ions onto chitosan and its sulfoethyl derivative.     

Synthesis, characterization and metal uptake capacity of a new carboxymethyl chitosan derivative

Chemical modification of chitosan (Cs) and its derivatives via graft copolymerization can enhance their properties and consequently expands their potential applications. Carboxymethyl chitosan (CMCs) was prepared and characterized by FTIR spectroscopy, elemental analysis and X-ray diffraction. Graft copolymerization of N-acryloylglycine (NAGly) onto CMCs using 2,2-dimethoxy-2-phenyl acetophenone (PI) as photoinitiator was carried out under nitrogen atmosphere in aqueous solution. Evidence of grafting was confirmed by comparison of FTIR spectra of CMCs and the graft copolymers as well as the 2D-X-ray diffraction patterns, elemental analysis and the difference in solubility profiles before and after grafting. The effects of concentration of NAGly, PI and reaction time on the extent of grafting were investigated by determining the grafting percentage and grafting efficiency. With other conditions kept constant, the obtained optimum grafting conditions were: CMCs = 0.1 g, NAGly = 0.4 g, PI = 0.02 g and reaction time = 1 h. A preliminary study was then carried out to evaluate the capacity of the prepared new graft copolymer to uptake copper ions from aqueous systems. This preliminary investigation of the prepared graft copolymers showed that they may be tailored and exploited to expand the utilization of these systems in metal ions uptake and treatment of wastewater.     

Framework control by a metalloligand having multicoordination ability: new synthetic approach for crystal structures and magnetic properties

By utilizing the novel metalloligand l(Cu), [Cu(2,4-pydca)(2)](2)(-) (2,4-pydca(2)(-) = pyridine-2,4-dicarboxylate), which possesses two kinds of coordination groups, selective bond formation with the series of the first-period transition metal ions (Mn(ii), Fe(ii), Co(ii), Cu(ii), and Zn(ii)) has been accomplished. depending on the coordination mode of 4-carboxylate with Co(ii), Cu(ii), and Zn(ii) ions, L(Cu) forms a one-dimensional (1-d) assembly with a repeating motif of [-M-O(2)C-(py)N-Cu-N(py)-Co(2)-]: {[ZnL(Cu)(H(2)O)(3)(DMF)].DMF}(N)() (2), [ZnL(Cu)(H(2)O)(2)(MeOH)(2)](N)() (3), and {[ML(Cu)(H(2)O)(4)].2H(2)O}(N)() (M = Co (4), Cu (5), Zn (6)). the use of a terminal ligand of 2,2'-bipyridine (2,2'-bpy), in addition to the cu(ii) ion, gives a zigzag 1-d assembly with the similar repeating unit as 4-6: {[Cu(2,2'-bpy)L(Cu)].3H(2)O}(N)() (9). on the other hand, for Mn(ii) and Fe(ii) ions, L(Cu) shows a 2-carboxylate bridging mode to form an another 1-d assembly with a repeating motif of [-M-O-C-O-CU-O-C-O-]: [ML(Cu)(H(2)O)(4)](N)() (M = Mn (7), Fe (8)). this selectivity is related to the strength of lewis basicity and the electrostatic effect of L(Cu) and the irving-williams order on the present metal ions. according to their bridging modes, a variety of magnetic properties are obtained: 4, 5, and 9, which have the 4-carboxypyridinate bridge between magnetic centers, have weak antiferromagnetic interaction, whereas 7 and 8 with the carboxylate bridge between magnetic centers reveal 1-d ferromagnetic behavior (Cu(II)-M(II); M(II) = Mn(II), J/k(B) = 0.69 K for 7; M(II) = Fe(II), J/k(B) = 0.71 K for 8).     

Latrunculins: NMR study,two new toxins and a synthetic approach

A complete ¹H and ¹³C NMR assignment of one of the latrunculins (B) was accomplished with the aid of 2D NMR COSY and CH shift-correlation experiments. The various H-H Coupling constants have been datermined and a conformation of the macrolide and the tetrahydropyran (THP) ring suggested on basis of the J-values and measured NOE's. The absolute configuration of latrunculin-A($\text{1}$) was determined on the grounds of its earlier X-Ray analysis, and a chemical degradation to a known compound. Two novel latrunculins, -C($\text{3}$) and -D($\text{4}$), were isolated from the Red Sea sponge $\text{L. magnifica}$ and their structures elucidated. Starting with L-cysteine a synthon for the latrunculins has been synthesized.     

Experimental design approach in optimizing the sorption properties of a new generation of reinforced porous hybrid beads

A new sorbent called reinforced porous hybrid beads (RPHB) based on an Algerian aluminium pillared montmorillonite (Al-PIMt)/polyvinyl alcohol (PVA) and calcium carbonate (CC) was prepared using the extrusion method. These new composite bead sorbents were characterized by Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The mechanical properties for a series of wet RPHB are measured using uniaxial compression tests. These RPHB beads were used in the batch mode sorption of malachite green (MG) in aqueous solution.The effects of independent variables such as the initial concentration of MG, the sorbent dose and the pH of the suspension as well as their interactions during sorption processes are investigated. A Box–Behnken design based on the response surface methodology (RSM) is applied to evaluate the main effects of the variables. The response in term of the MG removal efficiency is maximized. The study of the interactions between the three variables shows that the initial concentration of MG and the pH of the aqueous media appear to be the most significant variables which significantly affect the elimination of MG. The optimal values favorable for the best sorption of MG on these new porous beads are an initial concentration of MG (92.36 mg L⁻¹), a pH of the aqueous medium (pH = 5.01) as well as the dose of the RPHB sorbent (1.03 g L⁻¹).Statistical analysis results show a good correlation between the experimental results and those predicted with a very satisfactory coefficient of determination value (R² = 0.99).     

Synthesis, characterization, and sorption properties of silica gel-immobilized pyrimidine derivative

5-Benzylidene-2-thiobarbituric acid (BzTBA), a pyrimidine derivative, was used to modify the surface of silica gel-chloropropyltrimethoxysilane (Si-Cl) via chemical immobilization to produce a new pyrimidine silica phase (Si-BzTBA). Identification of the surface modification was characterized and performed on the basis of infrared as well as elemental analysis. Thermal desorption method was found to give 0.129-0.143 mmol g(-1) as surface coverage values. Metal sorption properties of Si-BzTBA were also studied and the evaluated results refer to the high metal sorption of Si-BzTBA for copper(II), mercury(II), cadmium(II), and lead(II) with the same order. These four Si-BzTBA-metal complexes were also synthesized and the stoichiometric ratios were identified as 1:1 except lead complex was found to give a 1:2 ratio. Electron impact-mass spectrometric analysis (EI-MS) with 70 eV ionization energy was used as a potential thermal method for the confirmation of surface modification of Si-BzTBA and its metal complexes based on fragmentation elucidation of thermally desorbed ion peaks. The EI-MS of Si-BzTBA was found to show several characteristic fragment ion peaks that are directly related to the chemical binding of BzTBA to SiCl phase. Differential scanning calorimetry study (DSC) was also performed to evaluate the various kinetic and thermodynamic parameters of thermal degradation processes and have been enumerated. The results of EI-MS and DSC are very similar in many respects.     

N-2-(2-pyridyl)ethyl chitosan: Synthesis in gel and sorption properties

A procedure was developed for preparing a new heterocyclically substituted chelating aminopolymer, N-2-(2-pyridyl)ethyl chitosan, by direct addition of 2-vinylpyridine to chitosan under the conditions of synthesis in gel. The resulting polymer has the degree of substitution of up to 1. The ability of the samples obtained to sorb transition and noble metal ions was evaluated.     

Synthesis, characterization, and sorption properties of silica gel-immobilized Schiff base derivative

Silica gel was derivatized with benzophenone 4-aminobenzoylhydrazone (BAH), a Schiff base derivative, after silanization of silica by 3-chloropropyltrimethoxysilane (CPTS) by using a reported method. Characterization of the surface modification was confirmed through infrared spectroscopy, thermogravimetry, and elemental analysis. The immobilized surface was used for Cu(II), Ni(II), Zn(II), and Co(II) sorption from aqueous solutions. The influence of the amount of sorbent, ion concentration, pH, and temperature was investigated. The sorption data followed Langmuir, Freundlich, and Dubinin-Radushkevich (D-R) isotherms. The mean sorption energy (E) of benzophenone 4-aminobenzoylhydrazone (BAH) immobilization onto silica gel was calculated from D-R isotherms, indicating a chemical sorption mode for four cations. Thermodynamic parameters, i.e., DeltaG, DeltaS, and DeltaH, were also calculated for the system. From these parameters, DeltaH values were found to be endothermic: 27.0, 22.7, 32.6, and 34.6 kJ mol(-1) for Cu(II), Ni(II), Co(II), and Zn(II) metal ions, respectively. DeltaS values were calculated to be positive for the sorption of the same sequence of divalent cations onto sorbent. Negative DeltaG values indicated that the sorption process for these three metal ions onto immobilized silica gel is spontaneous.     

A new synthetic approach to benzomorphans

A new approach to the synthesis of benzomorphan derivatives is exemplified by the obtention of 3,6-dimethyl-benzomorphan from the readily available 1-methyl-2,3-benzobicyclo-[3,2,l]octane-4,6-dione.     

A new synthetic approach to phosphatidylethanolamine

A new synthetic method for phosphatidylethanolamine head group was developed via ring-opening of cyclic dioxaphospholane 2 with sodium azide and subsequent hydrogenation.The advantage of this strategy included short reaction steps,readily available materials and good yields.     

Synthesis and properties of a new fluorescent bicyclic 4-N-carbamoyldeoxycytidine derivative

[reaction: see text] A bicyclic 4-N-carbamoyldeoxycytidine derivative (1, dC(hpp)) geometrically locked was synthesized as a new fluorescent nucleobase. The hybridization properties of oligodeoxynucleotides containing dC(hpp) were investigated by use of T(m) analysis. It was found that dC(hpp) forms stable base pairs not only with the complementary guanine base, but also with the adenine base. Interestingly, the fluorescence of dC(hpp) was suppressed only when a dC(hpp)-dG base pair was formed.     

A new synthetic approach to 7-hydroxynitidine

Benzo[c]phenanthridine alkaloid, 7-hydroxynitidine, was synthesized from readily available 2-benzyloxy-6-bromo-3,4-dimethoxybenzaldehyde 5 and napthylamine 6 using reductive amination followed by radical cyclization in eight steps. This method is highly efficient and better way to synthesize fully aromatized benzo[c]phenanthridine compounds.