scholarly journals Measurement of Complex Formation Process of Nickel (II) with Freshwater Fulvic Acids Using the Solubility Method

2021 ◽  
pp. 54-61
Author(s):  
T. Makharadze ◽  
G. Makharadze
Keyword(s):  
Molecular Weight ◽  
Complex Formation ◽  
Formation Process ◽  
Molar Mass ◽  
Solid Phase ◽  
Average Molecular Weight ◽  
Free Ligand ◽  
Fulvic Acids ◽  
Solubility Method ◽  
Complex Formation Process

The complex formation process between Ni(II) and fulvic acids has been studied through the solubility method at pH = 9.0. The old suspension of Ni(OH)2 is used as a solid phase. Fulvic acids are isolated from Paravani lake by the adsorption-chromatographic method. The activated charcoal is used as a sorbent. The concentration of fulvic acids in model solutions changes from 1.1 × 10-5 mol/L to 4.4 × 10-5 mol/L. The value of molar mass of fulvic acids at pH = 9.0 was taken into consideration for the calculation of molar concentrations of fulvic acids. Before adding the ligand the initial concentration of nickel was 3.8 × 10-6 mol/L. This article has shown that, during complex formation process every 0.25 part of an associate of fulvic acids (Mw = 7610), inculcates into nickel's inner coordination sphere as an integral ligand, so it may be assumed, that the average molecular weight of the associate of fulvic acids which takes part in complex formation process equals to 1903. This part of the associate of fulvic acids was conventionally called the "active associate". The average molecular weight of the "active associate" was used for determining the concentration of free ligand and average stability constant (1:1), which equals to β = 1.07 × 107 (lgβ = 7.03).

scholarly journals Investigation of Complex Formation Process of Copper with Macromolecular Organic Substances, Isolated from Natural Waters

2020 ◽  
pp. 1-5
Author(s):  
Giorgi Makharadze ◽  
Tamar Makharadze
Keyword(s):  
Heavy Metals ◽  
Molecular Weight ◽  
Complex Formation ◽  
Stability Constants ◽  
Formation Process ◽  
Natural Waters ◽  
Average Molecular Weight ◽  
Fulvic Acids ◽  
Organic Substances ◽  
Complex Formation Process

Natural macromolecular organic substances-fulvic acids take an active part in complex formation processes and stipulate migration forms of heavy metals in natural waters The calculation of the migration forms of heavy metals is one of the problematic issue of the contemporary chemistry, which couldn’t be solved without using the conditional stability constants of fulvate complexes. In spite of researches, experimental data on stability constants of complex compounds of fulvic acids with heavy metals ( among them copper) are heterogeneous and they differ in several lines from each other. One of the reason of such condition is ignoring an average molecular weight of the associates of fulvic acids, which finally causes the wrong results. Complex formation process between copper (II) and fulvic acids was studied by the solubility method at pH=9.0. Cu(OH)2 suspension was used as a solid phase. Fulvic acids were isolated from Paravani lake by the adsorption –chromatographic method. In this article is shown that, during complex formation process every 1/4 part of an associate of fulvic acids(Mw=7610), inculcates into copper's inner coordination sphere as an integral ligand, so it may assume, that the average molecular weight of the associate of fulvic acids which takes part in complex formation process equals to 1903. This part of the associate of fulvic acids was conventionally called an“active associate".The average molecular weight of the“active associate”was used for determination the composition of copper fulvate complex, the concentration of free ligand and stability constant, which equals to 2,25x107   

scholarly journals Influence of acceptor functionality on charge transfer interactions in mixtures of poly(9-vinylcarbazole) with nitroaromatic compounds

2012 ◽  
Vol 10 (2) ◽  
pp. 313-319 ◽  
Author(s):  
Anca Grigoras ◽  
Virgil Barboiu
Keyword(s):  
Molecular Weight ◽  
Charge Transfer ◽  
Complex Formation ◽  
Charge Transfer Complex ◽  
Average Molecular Weight ◽  
Nitro Compounds ◽  
Nitroaromatic Compounds ◽  
Association Constants ◽  
Electron Acceptors ◽  
Weight Average Molecular Weight

AbstractCharge transfer interactions in mixtures of poly(9-vinylcarbazole) with three nitro compounds (4,4′dinitrodibenzyl, ethyl 3,5-dinitrobenzoate and 2,2′,4,4′-tetranitrodibenzyl) were examined. GPC shows an increase of apparent polymer weight average molecular weight (MW) in mixtures compared with pure PVK. Electron acceptors show upfield 1H-NMR shifts for all mixtures. The equilibrium association constants (k) calculated from the Benesi-Hildebrand equation are 0.511, 1.371, and 1.868 L mol−1 for PVK blends with DNDB, DNBE and TNDB, respectively. Shifts of (−NO2) stretch vibrations in mixtures support charge transfer complex formation between PVK chains and electron acceptors The ability to accept electrons decreases: TNDB>DNBE>DNDB.

scholarly journals Low Molar Mass Dextran: One-Step Synthesis With Dextransucrase by Site-Directed Mutagenesis and its Potential of Iron-Loading

2021 ◽  
Vol 9 ◽  
Author(s):  
Tingting Wang ◽  
Zhiming Jiang ◽  
Yiya Wang ◽  
Hao Wu ◽  
Yan Fang ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Molar Mass ◽  
Average Molecular Weight ◽  
Iron Complex ◽  
Site Directed Mutagenesis ◽  
Chain Elongation ◽  
Directed Mutagenesis ◽  
Iron Loading ◽  
Amino Acid Residues ◽  
Elongation Process

Iron dextran is a common anti-anemia drug, and it requires low molar mass dextran as substrate. In this work, we selected 11 amino acid residues in domain A/B of DSR-MΔ2 within a 5-angstrom distance from sucrose for site-directed mutagenesis by molecular docking. Mutation of Q634 did not affect the enzyme catalytic activity, but showed an obvious impact on the ratio of low molecular weight dextran (L-dextran, 3,000–5,000 Da) and relatively higher molecular weight dextran (H-dextran, around 10,000 Da). L-dextran was the main product synthesized by DSR-MΔ2 Q634A, and its average molecular weight was 3,951 Da with a polydispersity index <1.3. The structural characterization of this homopolysaccharide revealed that it was a dextran, with 86.0% α(1→6) and 14.0% α(1→4) glycosidic linkages. Moreover, L-dextran was oxidized with NaOH and chelated with ferric trichloride, and an OL-dextran-iron complex was synthesized with a high iron-loading potential of 33.5% (w/w). Altogether, mutation of amino acids near the sucrose binding site of dextransucrase can affect the chain elongation process, making it possible to modulate dextran size.

Preparation of High-Molecular-Weight Poly(glycolic acid) by Direct Melt Polycondensation from Glycolic Acid

2013 ◽  
Vol 821-822 ◽  
pp. 1023-1026 ◽  
Author(s):  
Kai Shen ◽  
Sheng Lin Yang
Keyword(s):  
Molecular Weight ◽  
High Molecular Weight ◽  
Glycolic Acid ◽  
Solid Phase ◽  
Zinc Acetate Dihydrate ◽  
Average Molecular Weight ◽  
High Vacuum ◽  
Polymerization Time ◽  
Direct Melt Polycondensation ◽  
High Molecular Weight Poly

Relatively high molecular weight poly(glycolic acid)(PGA) was prepared by improved melting polycondensation of glycolic acid. Firstly, two kinds of catalyst, zinc acetate dihydrate and tin dichloride dehydrate, were utilized respectively, and a selection was made according to the molecular weight of final product. It has been found that the tin catalyst was the better one. Then the catalyst usage, the heating program, the polymerization time, as well as the vacuum condition were optimized. It was found that the high vacuum at 220~230°C contributed much to the molecular weight to the polymer, however, the polymerization time should be less than 1.5hr to avoid the discolor of the product. Finally, the PGA with a weight average molecular weight of 45,000g/mol were obtained directly without solid phase polycondensation, which was rather higher than some reported previously. The structure and properties of PGA were also characterized by means of intrinsic viscosity, FTIR, NMR and DSC testing.

Effect of the molecular weight on the lower critical solution temperature of poly(N,N-diethylacrylamide) in aqueous solutions

2001 ◽  
Vol 79 (12) ◽  
pp. 1870-1874 ◽  
Author(s):  
D G Lessard ◽  
M Ousalem ◽  
X X Zhu
Keyword(s):  
Molecular Weight ◽  
Lower Critical Solution Temperature ◽  
Molar Mass ◽  
Average Molecular Weight ◽  
Solution Temperature ◽  
Low Molecular Weight ◽  
Fractional Precipitation ◽  
Critical Solution Temperature ◽  
Molecular Weight Dependence ◽  
Critical Molecular Weight

The molecular weight dependence of the lower critical solution temperature of poly(N,N-diethylacrylamide) was studied with 11 samples of the polymer with a number-average molecular weight (Mn) ranging from 9.6 × 103 to 1.3 × 106 g mol–1 and relatively narrow polydispersity indices from 1.19 and 2.60. These samples were obtained by fractional precipitation of the polymer. LCST values of polymers were measured by turbidimetry and microcalorimetry. An inverse dependence of LCST on the molar mass was found and the LCST of the samples remained more or less a constant above a critical molecular weight of ca. 2 × 105 g mol–1. The enthalpy and the entropy changes as well as the LCST of the polymer depend strongly on the molar mass of the polymer, especially in low molecular weight range.Key words: poly(N,N-diethylacrylamide), LCST, thermosensitive, phase diagram, effect of molecular weight.

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