This work reports a study about the adsorption of the herbicides diquat and difenzoquat from aqueous medium employing polyurethane foam (PUF) as the adsorbent and sodium dodecylsulfate (SDS) as the ...counter ion. The adsorption efficiency was shown to be dependent on the concentration of SDS in solution, since the formation of an ion-associate between cationic herbicides (diquat and difenzoquat) and anionic dodecylsulfate is a fundamental step of the process. A computational study was carried out to identify the possible structure of the ion-associates that are formed in solution. They are probably formed by three units of dodecylsulfate bound to one unit of diquat, and two units of dodecylsulfate bound to one unit of difenzoquat. The results obtained also showed that 95% of both herbicides present in 45mL of a solution containing 5.5mgL−1 could be retained by 300mg of PUF. The experimental data were well adjusted to the Freundlich isotherm (r2 ≥ 0.95) and to the pseudo-second-order kinetic equation. Also, the application of Morris-Weber and Reichenberg equations indicated that an intraparticle diffusion process is active in the control of adsorption kinetics.
•This paper reports the use of low-cost polyurethane foam for the removal of diquat and difenzoquat from water.•Results obtained indicated that dodecylsulfate ion has a fundamental role in the adsorption process.•A possible structure of the ion-associate formed between diquat and difenzoquat and dodecylsulfate is proposed.•The adsorption process followed a pseudo-second-order kinetics.•Quantitative removal of the herbicides by PUF was observed.
To investigate the herbicidal potential of 2,5-diketopiperazines (2,5-DKPs), we applied a known protocol to produce a series of 2,5-DKPs through intramolecular N-alkylation of Ugi adducts. However, ...the method was not successful for the cyclization of adducts presenting aromatic rings with some substituents at the ortho position. Results from DFT calculations showed that the presence of voluminous groups at the ortho position of a benzene ring results in destabilization of the transition structure. Lower activation enthalpies for the SN2-type cyclization of Ugi adducts were obtained when bromine, instead of a chlorine anion, is the leaving group, indicating that the activation enthalpy for the cyclization step controls the formation of the 2,5-DKP. Some Ugi adducts and 2,5-DKPs formed crystals with suitable qualities for single-crystal X-ray diffraction data collection. Phytotoxic damage of some 2,5-DKPs on leaves of the weed Euphorbia heterophylla did not differ from those caused by the commercial herbicide diquat.
In this work, we present the dielectric behavior of water with a novel flexible model, FAB/
ϵ
, that improved three-site water models. Different concentrations of the ionic liquid ...1-butyl-3-methylimidazolium bmim and bis(trifluoromethanesulfonyl)imide
Tf
2
N with water have been investigated. The study was performed by molecular dynamics simulations using three water models, being two non-polarizable 3-site SPC/E and SPC/e and a flexible 3-site FAB/
ϵ
model. Systematic thermodynamics and dynamical and dielectric properties were investigated, such as density, self-diffusion coefficient, heat of vaporization
Δ
H
vap
, and surface tension at 300 K and 1 bar. Extrapolating the experimental molar fraction of the mixtures, a pattern change for all properties was observed, evidencing the phase separation previously reported by experimental data. The results also show the dielectric effect in the system, which is important in ionic systems and fundamental for understanding why this ionic liquid behaves hydrophobic.
We performed density functional theory (DFT) calculations using the WB97Xd functional with a dispersion correction term and the 6-31G(d,p) basis set to study the contributions of π–π stacking and ...hydrogen-bonding interactions to the aggregation of asphaltene model compounds containing a 2,2′-bipyridine moiety covalently bonded to one (monosubstituted) and two (disubstituted) aromatic hydrocarbon moieties (phenyl, naphthyl, anthracyl, phenanthryl, and pyrenyl) through ethylene tethers. In these compounds, the N atoms of the 2,2′-bipyridine moiety provide lone pairs for hydrogen bonding to water molecules present in solution. The aggregation strength of the homodimers of these model compounds is evaluated in terms of the aggregation energies, enthalpies, and ΔG 298, as well as the π–π interaction distances. Geometry optimization and thermochemistry analysis results show that the homodimers of both mono- and disubstituted compounds are stable and have a negative ΔG 298 of aggregation because of π–π stacking interactions. Two water bridges containing one, two, or three water molecules per bridge span between two monomers and provide additional stabilization of the homodimers because of hydrogen bonding. The stabilization of the monosubstituted homodimers is the largest with two water molecules per bridge, whereas the stabilization of the disubstituted homodimers is the largest with three water molecules per bridge. The calculated 1H nuclear magnetic resonance chemical shifts for the monomers and dimers of the three model compounds of this series synthesized to date are in excellent agreement with experimental results for dilute and concentrated solutions in chloroform, respectively ( Tan X. ; Fenniri H. ; Gray M. R. Water enhances the aggregation of model asphaltenes in solution via hydrogen bonding. Energy Fuels 2009, 23, 3687 ). The ΔH and ΔG 298 results show that hydrogen bonding is as important as π–π interactions for asphaltene aggregation.
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•Ten enamine naphthoquinones were satisfactorily synthesized.•The antiproliferative activity were determined in four human cancer line cell.•Qualitative Structure/Biological Activity ...relationship was made.•Docking indicated that molecules inhibit topoisomerase and thymidylate synthase.
We synthesized ten enamine naphthoquinones with yields ranging from 43 to 76%. These compounds were screened for their in vitro antiproliferative activities by MTT assay against four types of human cancer cell lines: HCT116, PC3, HL60 and SNB19. The naphthoquinones bearing the picolylamine (7) and quinoline (12) moieties were the most actives (IC50 < 24 μM for all the cell lines), which were comparable or better to the values obtained for the control drugs. In silico evaluations allowed us to develop a qualitative Structure-Activity Relationship which suggest that electrostatic features, particularly the C2–C3 internuclear repulsion and the molecular dipole moment, relate to the biological response. Furthermore, Molecular Docking simulations indicate that the synthetic compounds have the potential to act as anticancer molecules by inhibiting topoisomerase-II and thymidylate synthase.
DFT calculations using the B3LYP and PBE1PBE functionals with the standard 6-31G(d) and 6-311+G(2d,p) basis sets were carried out for the 3-(2-phenylhydrazone)-naphthalene-1,2,4-trione system in ...solution (dmso) and in the gas phase, and showed the keto-hydrazone forms (rotamers Ia and Ib) to be more stable than the enol-azo forms (rotamers IIa and IIb, by about 14 kcal mol-1) and III (by approximately 6 kcal mol-1), independently of the nature of the substituent in the phenylene ring. These results were confirmed by spectroscopic data on the derivatives HL1-HL13, obtained from 2-hydroxy-1,4-naphthoquinone and arylamines (R = 4-OMe, 4-N2-C6H5, 4-Cl, 4-I, 3-I, 2-I, 4-COOH, 3-COOH, 4-CN, 3-CN, 4-NO2, 3-NO2, 2-NO2). The in vitro antitumor (against SF-295, HCT-8, MDAMB-435 and HL-60 cancer cell lines) and antibacterial activities (Bacillus cereus, Bacillus subtilis, Enterococcus faecalis, Staphylococcus aureus, Escherichia coli, Klebsiella pneumonia and Pseudomonas aeruginosa) of compounds HL1-HL13 and of their respective copper(II) complexes, Cu(L1-13)2, were tested. In general, these compounds exhibited low antibacterial activity, except for HL5 (R = 3-I), more active than the control; however, the corresponding complex was inactive. In contrast, increased cytotoxicity was observed upon complexation. Complex Cu(L13)2 (R = 3-NO2) presented moderate cytotoxicity against human leukemia (HL-60).
Novel 2-(R-phenyl)amino-3-(2-methyl-propenyl)-1,4-naphthoquinones (R = H, 4-OMe, 4-Ferrocenyl, 4-Me, 3-Me, 4-I, 3-I, 4-CN, 3-CN, 4-NO2 and 3-NO2) derived from nor-lapachol ...2-hydroxy-3-(2-methylpropenyl)-1,4-naphthoquinone were obtained in good yields. Their structures were proposed on the basis of a single crystal X-ray diffraction study (R = OMe, 2b), ¹H and 13C NMR studies and calculations using the B3LYP functional and the 6-311+G(2d,p) basis set. The half-wave potentials of the aminonaphthoquinones and ¹H NMR chemical shifts of the 3-propenyl hydrogen in 2a-k show good correlation with the substituent Hammett constants on the phenylamino ring. The antitumor assays showed promising activity for substrate methoxy-nor-lapachol 1 and the 4-ferrocenyl derivative 2c.
This paper represents an extension of our work on the (1)H and (13)C NMR chemical shifts of norbornane and 2-endo-norborneol. NCS-NBO analysis was employed to probe contributions of bond orbitals and ...orbitals of lone pairs to nuclear shielding in conformers of the alcohol generated by rotation of the C-O bond. Variations in (1)H and (13)C chemical shifts with the dihedral angle are discussed in terms of Lewis and non-Lewis partitioning and their respective importance is evaluated. In addition to hyperconjugation of the lone pair in a p orbital of oxygen that was previously reported, a sizable participation of the lone pair which is in an sp orbital is also observed and their combined effect dominates the carbon chemical shifts of the C(1)-C(2)-OH and C(3)-C(2)-OH fragments. Both lone pairs on oxygen also contribute to localized, though-space effects on nuclei in the vicinity, these effects answering for the largest deviations in hydrogen chemical shifts on rotation around the C-O bond. On the other hand, for conformers in which nonbonded repulsions lead to distortions in the molecular framework, variations in chemical shifts may be attributed to angular effects.
Experimental
1H chemical shift analysis for the camphor-based chiral γ-amino alcohol
2 shows a difference of 0.9
ppm for the two diastereotopic hydrogens H
11a and H
11b. In contrast, for the
exo ...adduct (
1) and its acetate (
3) these hydrogens have very similar chemical shifts. DFT calculations followed by NBO analysis show that these differences in chemical shifts arise as a consequence of an intramolecular hydrogen bond O
H⋯N in
2, which restricts its conformational mobility. In the most stable conformer of
2, the interaction of the nitrogen lone-pair with the vicinal
σ
*(C
H
11a) antibonding orbital shifts that hydrogen downfield by 0.9
ppm. This is confirmed by experimental NMR studies based on NULL.
This paper represents an extension of our work on the 1H and 13C NMR chemical shifts of norbornane and 2-endo-norborneol. NCS−NBO analysis was employed to probe contributions of bond orbitals and ...orbitals of lone pairs to nuclear shielding in conformers of the alcohol generated by rotation of the C−O bond. Variations in 1H and 13C chemical shifts with the dihedral angle are discussed in terms of Lewis and non-Lewis partitioning and their respective importance is evaluated. In addition to hyperconjugation of the lone pair in a p orbital of oxygen that was previously reported, a sizable participation of the lone pair which is in an sp orbital is also observed and their combined effect dominates the carbon chemical shifts of the C1−C2−OH and C3−C2−OH fragments. Both lone pairs on oxygen also contribute to localized, though-space effects on nuclei in the vicinity, these effects answering for the largest deviations in hydrogen chemical shifts on rotation around the C−O bond. On the other hand, for conformers in which nonbonded repulsions lead to distortions in the molecular framework, variations in chemical shifts may be attributed to angular effects.
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