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Displaying Results 1 - 4 of 4 on page 1 of 1

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Catalysis of the deprotonation of β-diketones during formation of the 1:1 metal complexes (2018)

Blanco, Carlos A.; Hynes, Michael J.

Catalysis of the deprotonation of β-diketones during formation of the 1:1 metal complexes (2018)

Blanco, Carlos A.; Hynes, Michael J.

Abstract:

Catalytic effects on the deprotonation rate constants of beta-diketones were observed during kinetic studies of the formation reactions of the 1:1 complexes of these ligands. When vanadium(IV), chromium(III), iron(III), cobalt(II), nickel(II), copper(II), and uranium(VI) react with pentane-2,4-dione, heptane-3,5-dione, 1,1,1-trifluoropentane-2,4-dione, 4,4,4-trifluoro-1-(2-thienyl)-butane-1,3-dione, 1-phenylbutane-1,3-dione, and 2-acetylcyclohexanone a significant catalytic effect on the rate of ionization of the keto tautomer of the ligand was observed. A considerable enhancement of the rate of ionization of the enol tautomers of these ligands was observed during the complex formation reactions with Cu2+. A mechanism is proposed that accounts for these catalytic effects. In the case of Cu2+ the increased rate of proton removal from the ligands may be rationalized in terms of the relatively large reduction potential of this metal ion.

http://hdl.handle.net/10379/8879

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Contribution of the empirical dispersion correction on the conformation of short alanine peptides obtained by gas-phase qm calculations (2018)

Fadda, Elisa; Woods, Robert J.

Contribution of the empirical dispersion correction on the conformation of short alanine peptides obtained by gas-phase qm calculations (2018)

Fadda, Elisa; Woods, Robert J.

Abstract:

In this work we analyze the effect of the inclusion of an empirical dispersion term to standard DFT (DFT-D) in the prediction of the conformational energy of the alanine dipeptide (Ala2) and in assessing the relative stabilities of short polyalanine peptides in helical conformations, i.e., alpha and 3(10) helices, from Ala4 to Ala16. The Ala2 conformational energies obtained with the dispersion-corrected GGA functional B97-D are compared to previously published high level MP2 data. Meanwhile, the B97-D performance on larger polyalanine peptides is compared to MP2, B3LYP and RHF calculations obtained at a lower level of theory. Our results show that electron correlation affects the conformational energies of short peptides with a weight that increases with the peptide length. Indeed, while the contribution of vdW forces is significant for larger peptides, in the case of Ala2 it is negligible when compared to solvent effects. Even for short peptides, the inclusion of an empirical disp...

http://hdl.handle.net/10379/11391

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Kinetics, isotherm, and thermodynamic studies of methylene blue adsorption on polyaniline and polypyrrole macro-nanoparticles synthesized by C-Dot-initiated polymerization (2018)

Maruthapandi, Moorthy; Kumar, Vijay Bhooshan; Luong, John H. T.; Gedanken, Aharon

Kinetics, isotherm, and thermodynamic studies of methylene blue adsorption on polyaniline and polypyrrole macro-nanoparticles synthesized by C-Dot-initiated polymerization (2018)

Maruthapandi, Moorthy; Kumar, Vijay Bhooshan; Luong, John H. T.; Gedanken, Aharon

Abstract:

This work unraveled kinetics, isotherm, and thermodynamic properties of methylene blue (MB) adsorbed on polyaniline (PANI) and polypyrrole (PPY). The two polymers, PANI and PPY, synthesized by a facile C-dot (CD)-initiated polymerization method have been proven as the effective adsorbent materials to remove MB from wastewater. This dye model is also generally employed as a redox indicator in analytical chemistry and exhibits blue in an oxidizing environment, but it is colorless when exposed to a reducing agent. The effects of temperature, adsorbent amount contact time, and dye concentration were consistently examined. The adsorption capacity of the polymers at 28 degrees C could reach 19.2 mg/g. The adsorption equilibrium of the dye was attained after 90 and 120 min of contact time with PANI and PPY, respectively. The equilibrium details were well described by Freundlich and Langmuir isotherms. Results showed that PANI and PPY prepared using CD-initiated polymerization are better ad...

http://hdl.handle.net/10468/6681

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Synthesis of n-[(dialkylamino)methyl)]acrylamides and n-[(dialkylamino)methyl]methacrylamides from schiff base salts: useful building blocks for smart polymers (2018)

Alzahrani, Abdullah; Mirallai, Styliana I; Chalmers, Benjamin A; McArdle, Patrick; Alda...

Synthesis of n-[(dialkylamino)methyl)]acrylamides and n-[(dialkylamino)methyl]methacrylamides from schiff base salts: useful building blocks for smart polymers (2018)

Alzahrani, Abdullah; Mirallai, Styliana I; Chalmers, Benjamin A; McArdle, Patrick; Aldabbagh, Fawaz

Abstract:

The traditional thermal Mannich reaction is unsuitable for preparing polymerizable N-methylene amino substituted acrylamides and methacrylamides. Herein we provide a facile multi-gram high yield synthesis of these monomeric precursors to stimuli-responsive polymers by the addition of acrylamides and methacrylamides onto in situ generated or freshly isolated methylene Schiff base (iminium) salts. The X-ray crystal structure of the hydrated iminium salt, 1-(hydroxymethyl)azocan-1-ium chloride and monomer center dot HCl salt (N-[(azocan-1-yl)methyl]prop-2-enamide hydrochloride) is described.

http://hdl.handle.net/10379/10235

Displaying Results 1 - 4 of 4 on page 1 of 1