Rate constants for the gas-phase reactions of O3 with a series of monoterpenes and related compounds at 296 ± 2 K

Rate constants for the gas-phase reactions of O₃ with a series of monoterpenes and related compounds have been determined at 296 ± 2 K and 740 torr total pressure of air or O₂ using a combination of absolute and relative rate techniques. Good agreement between the absolute and relative rate data was observed, and the rate constants obtained (in units of 10^?17 cm³ molecule^?1 s^?1) were: α-pinene, 8.7; β-pinene, 1.5; Δ³-carene, 3.8; 2-carene, 24; sabinene, 8.8; d-limonene, 21; γ-terpinene, 14; terpinolene, 140; α-phellandrene, 190; α-terpinene, 870; myrcene, 49; trans-ocimene, 56; p-cymene, <0.005; and 1,8-cineole, <0.015. While these rate constants for α- and β-pinene and sabinene are in good agreement with recent absolute and relative rate determinations, those for the other monoterpenes are generally lower than the literature data by factors of ca. 2–10. The measured rate constants for the monoterpenes are reasonably consistent with predictions based upon the number and positions of the substituent groups around the 〉C?C〈 bond(s).     

Enantioseparations of non-benzenoid and oligo-Tröger’s bases by HPLC on Whelk O1 column

The separation of enantiomers of several ‘bis- and tris-Tröger’s bases’ by HPLC on commercially available chiral stationary phase Whelk O1 is described for the first time. The observed structure–enantioselectivity relationships are in agreement with the previously established molecular recognition model. For all ‘bis- and tris-Tröger’s bases’ studied, satisfactory to excellent enantioselectivities were observed.     

Rate constants for the reactions of the OH radical with the propyl and butyl nitrates and 1-nitrobutane at 298 ± 2 k

Using a relative rate method, rate constants for the gas-phase reactions of the OH radical with 1- and 2-propyl nitrate, 1- and 2-butyl nitrate and 1-nitrobutane have been determined in the presence of one atmosphere of air at 298 ± 2 K. Using rate constants for the reactions of the OH radical with propane and cyclohexane of 1.15 × 10^?12 and 7.49 × 10^?12 cm³ molecule^?1 s^?1, respectively, following rate constants (in units of 10^?12 cm³ molecule^?1 s^?1) were obtained: 1-propyl nitrate, 0.62; 2-propyl nitrate, 0.41; 1-butyl nitrate, 1.78; 2-butyl nitrate, 0.93; and 1-nitrobutane, 1.35. These rate constants are compared and discussed with the literature data.     

Synthesis of 3,3′-methylenebis(4-hydroxyquinolin-2(1H)-ones) of prospective anti-COVID-19 drugs

Molecular Diversity - During formylation of 2-quinolones by DMF/Et3N mixture, the unexpected 3,3′-methylenebis(4-hydroxyquinolin-2(1H)-ones) were formed. The discussed mechanism was proved as...     

Theoretical investigation of the weak interactions of rare gas atoms with silver clusters by resonance Raman spectroscopy modeling

The interactions of rare gas atoms (Rg = Ar, Kr, and Xe) with small neutral and cationic silver clusters have been investigated by density functional methods and the effect of these weak interactions on the resonance Raman spectra of the complexes has been evaluated. The resonance Raman technique that depends on the properties of ground and excited state, seems deeply sensitive to the weak rare gas–metal cluster interactions, and the use of inert gases has been proven to be an excellent approach to recognize the ability of this technique to detect extremely weak interactions. In this work, for , and complexes the IR, normal and resonance Raman spectra have been calculated and the effect of rare gas–cluster stretching vibration ( ) on the pattern and the relative intensities of different spectra have been investigated. The resonance Raman spectra for the weakly interacted complexes (with the interaction energies less than ?2.0 kcal/mol) exhibit the vibration with the detectable intensity that its intensity increases by going from Ag₆–Ar to Ag₆–Xe complex. Moreover, the resonance Raman spectra (based on the excited state gradient approximation) for high intensity nearly degenerate excited states, proved the effect of accumulation of the excited state charge density on the relative intensity of vibration.     

Polytetrafluoroethylene Sputtered PES Membranes for Membrane Distillation: Influence of RF Magnetron Sputtering Conditions

Thin films of fluorocarbon were deposited on polyethersulfone membranes via argon plasma sputtering of a poly(tetrafluoroethylene) (PTFE) target in an RF magnetron plasma reactor. The obtained deposited ultrathin coatings had nanoscale roughnesses and high degrees of fluorination. The intensity of fluorine atom in plasma environment during fluorocarbon deposition was investigated. Depending on the deposition conditions comprising working gas pressure, applied RF power, and distance between the target and the substrate, polymeric films with different chemical compositions and/or morphologies were obtained. The morphologies of the films were analyzed by means of SEM, XPS, and AFM. The results suggested that the sputtered film deposited at a higher pressure and longer target–substrate distance and moderate RF power had a surface composition and chemical structure closer to those of the PTFE film. The treated hydrophobic PES membranes with water contact angles as high as 115° were applied for the first time in an air gap membrane distillation setup for removal of benzene as a volatile organic compound from water. The results showed that the plasma-treated membranes have a comparable or superior performance to that of commercial PTFE used in membrane distillation with similar permeate flux and separation factor after 20 h long term performance.     

Solution and structural characterization of iron(II) complexes with ortho-halogenated phenolates: insights into potential substrate binding modes in hydroquinone dioxygenases

The new ligand cis,cis-1,3,5-tris-(E)-(tolylideneimino)cyclohexane (TACH-o-tolyl) forms a 1:1 complex with iron(II). Addition of substituted phenolates forms 1:1:1 ligand:iron:phenolate complexes, which have been characterized both in the solid state and in solution. There is complete binding of the phenolate to the complex only when there are ortho-halogens on the phenolate. The tertiary complexes with ortho-halo-substituted phenolates exhibit short Fe-halogen distances, and the complex containing a non-coordinating but similarly sized ortho-methyl phenolate has a significantly different conformation and coordination geometry. Therefore, it is likely that the metal-halogen interaction stabilizes the complexes. The iron(II)-halogen interaction in these complexes may explain the substrate specificity of PcpA and LinE, enzymes that preferentially bind phenols and hydroquinones containing halogen substituents in ortho positions.     

Ultrathin Carbon Film Electrodes from Vacuum‐Carbonised Cellulose Nanofibril Composite

A novel way to produce ultrathin transparent carbon layers on tin‐doped indium oxide (ITO) substrates is developed. The ITO surface is coated with cellulose nanofibrils (from sisal) via layer‐by‐layer electrostatic binding with poly(diallyldimethylammonium chloride) or PDDAC acting as the binder. The cellulose nanofibril‐PDDAC composite film is then vacuum‐carbonised at 500 °C. The resulting carbon films are characterised by atomic force microscopy (AFM), small angle X‐ray scattering (SAXS), wide‐angle X‐ray scattering (WAXS), and Raman methods. Smooth carbon films with good adhesion to the ITO substrate are formed. The electrochemical characterisation of the carbon films is based on the oxidation of hydroquinone and the reduction of benzoquinone in aqueous phosphate buffer media. A modest effect of the cellulose nanofibril‐PDDAC film on the rate of electron transfer is observed. The effect of the film on the rate of electron transfer after carbonisation is more dramatic. For a 40‐layer cellulose nanofibril‐PDDAC film after carbonisation a two‐order of magnitude change in the rate of electron transfer occurs presumably due to a better interaction of the hydroquinone/benzoquinone system with the electrode surface.     

Effects of ozone in surface modification and thermal stability of SEBS block copolymers

SEBS block copolymers were treated under mild conditions in an ozone atmosphere, producing very slightly chemically-modified surfaces. The thermal stability was analysed by chemiluminescence and related to morphological changes observed by AFM. The intrinsic thermal stability was diminished by ozone exposure, but the oxidation induction times were delayed which indicates an enhancement of thermal stability under oxidative conditions. Also, chemiluminescence analysis showed the presence of a typical order-disorder transition at temperatures around 120 °C. Two different sets of samples which showed different morphological patterns were imaged by AFM. The effects of micro-domain separation and inter-domain structure on thermal properties are discussed and explained by a coarsening of the internal interface induced by ozone. A detailed 2D Fourier transformed analysis of AFM images allowed us to identify a regular wrinkled nano-pattern induced by uniaxial strain combined with ozone treatment, offering new opportunities in applications ranging from organic electronics to bio-patterning.     

Application of thiophilic chromatography to deplete serum immunoglobulins in sample preparation for bidimensional electrophoresis

Serum is a typical sample for non-invasive studies in clinical research. Its proteome characterization is challenging, since requires extensive protein depletion. Methods used nowadays for removal of high-abundance proteins are expensive or show quite often a low loading capacity, which has strong repercussions on the number of samples and replicates per analysis.In order to deplete immunoglobulins (Igs) and albumin (HSA) from 1 mL serum samples, we have developed a protocol based on a combination of thiophilic chromatography, not previously used in clinical proteomics, and a HSA-specific resin. Ig/HSA-depleted samples, immunoglobulinome and albuminone were analyzed by 2-DE. Thiophilic chromatography, coupled with HSA-depletion, allows a good 2-DE resolution as well as the visualization of new spots. Moreover, it yields enough protein to evaluate technical variability and facilitate subsequent protein identification. To validate the protocol, we carried out a preliminary comparative study between triplicate Igs/HSA-depleted serum samples from healthy control individuals and recently diagnosed/untreated rheumatoid arthritis (RA) patients. RA patients showed several acute phase proteins, as well as additional serum proteins, differentially and significantly regulated.Therefore, thiophilic chromatography can be used as an efficient and economical method in 2-DE to deplete immunoglobulins from large human serum samples before a more extensive fractioning.