1,8-Naphthyridines. Part III. Synthesis of some 6-substituted-1,8-naphthyridin-2(1H)ones

The syntheses of some 1,8-naphthyridines substituted in the 6-position with heterocyclic groups are described. A synthetic route to 6-amino-5,7-dimethyl-1,8-naphthyridin-2(1H)one is also presented.     

ASCORBIC ACID AS A PHOTOOXIDATION INHIBITOR

Abstract— The rate constant for total quenching of singlet oxygen by ascorbic acid has been determined using the inhibition of the bleaching of 9, 10-dimethylanthracene by AA in pyridine. The rate constant was 8.4 × 10^-6 M ^-1 s^-1, as determined photochemically, and 1.06 10^-7 M ^-1 s^-1 as determined in a dark reaction.     

Radiation-Induced Degradation of a Series of Poly(vinyl Ethers)

The degradative effects of γ-radiation on diethyl ether solutions of poly(alkyl vinyl ethers) under a variety of conditions were studied by polymer molecular weight measurements. Poly(methyl vinyl ether) (PMVE), poly(ethyl vinyl ether) (PEVE), poly(isopropyl vinyl ether) (PIPVE), and poly(isobutyl vinyl ether) (PIBVE) exhibited similar degradative behavior, with G_(SC) values between 0.3 and 0.9 scissions/100 eV at 0°C. Chemically polymerized and radiation-polymerized PEVE samples gave comparable results. Chain degradation was much more pronounced for samples of poly(tert-butyl vinyl ether) (PTBVE) which yielded a G_(SC) value of 3.6 at 0°C. Degradation experiments conducted on PEVE in air resulted in significantly higher rates of scission: G_(SC) = 5.6 scissions/100 eV at 0°C. Chain scission was not measurably influenced by changing the solvent from diethyl ether to di-isopropyl ether. Increased polymer concentration was found to reduce the rate of polymer degradation.     

Assessment of Lewis-Acidic Surface Sites Using Tetrahydrofuran as a Suitable and Smart Probe Molecule

Measuring the Lewis-acidic surface sites in catalysis is problematic when the material‘s surface area is very low (S_BET ≤1 m² ⋅ g⁻¹). For the first time, a quantitative assessment of total acidic surface sites of very small surface area catalysts (MoO₃ as pure and mixed with 5–30 % CdO (wt/wt), as well as CdO for comparison) was performed using a smart new probe molecule, tetrahydrofuran (THF). The results were nearly identical compared to using another commonly used probe molecule, pyridine. This audition is based on the limited values of the surface area of these samples that likely require a relatively moderate basic molecule as THF with pK_b=16.08, rather than strong basic molecules such as NH₃ (pK_b=4.75) or pyridine (pK_b=8.77). We propose mechanisms for the interaction of vapour phase molecules of THF with the Lewis-cationic Mo and Cd atoms of these catalysts. Besides, dehydration of isopropyl alcohol was used as a probe reaction to investigate the catalytic activity of these catalysts to further support our findings in the case of THF in a temperature range of 175–300 °C. A good agreement between the obtained data of sample MoO₃-10 % CdO, which is characterised by the highest surface area value, the population of Lewis-acidic sites and % selectivity of propylene at all the applied reaction temperatures was found.     

Synthesis and carbon-13 nuclear magnetic resonance spectroscopy of 5,6-dihydro-2-methyl-1,4-oxathiin,trans-tetrahydro-1,4-benzoxathiin, 1,4-tetrahydro-[9,10]benzoxathiin,the 4-oxides, 4,4-dioxides and related acyclic compounds

The results of a ¹³C NMR spectral investigation involving 5,6-dihydro-1,4-oxathiins, 1,4-tetrahydro[9,10]benzoxathiin, trans-tetrahydro-1,4-benzoxathiin, and the corresponding sulfoxides and sulfones are reported. An interpretation involving a dipolar structure with (2p→2p)π conjugation as opposed to (2p→3d)π interactions with the vinyloxy sulfides seems consistent with trends in the ¹³C NMR shifts. For the sulfoxides and sulfones, the substitutent-induced chemical shift (SCS) effects at the β vinylic carbons (βSO and βSO₂ effects) are considerably less than those at sp³ carbons. The γSO and γSO₂ values at the sp²γ carbons indicate deshielding, in contrast to the shielding at the sp³ carbons.     

A phase I, randomized study of combined IL-2 and therapeutic immunisation with antiretroviral therapy

Background  

Fully functional HIV-1-specific CD8 and CD4 effector T-cell responses are vital to the containment of viral activity and disease progression. These responses are lacking in HIV-1-infected patients with progressive disease. We attempted to augment fully functional HIV-1-specific CD8 and CD4 effector T-cell responses in patients with advanced chronic HIV-1 infection.     

On planarity of compact, locally connected, metric spaces

Independently, Claytor [Ann. Math. 35 (1934), 809–835] and Thomassen [Combinatorica 24 (2004), 699–718] proved that a 2-connected, compact, locally connected metric space is homeomorphic to a subset of the sphere if and only if it does not contain K ₅ or K _3;3. The “thumbtack space” consisting of a disc plus an arc attaching just at the centre of the disc shows the assumption of 2-connectedness cannot be dropped. In this work, we introduce “generalized thumbtacks” and show that a compact, locally connected metric space is homeomorphic to a subset of the sphere if and only if it does not contain K ₅, K _3;3, or any generalized thumbtack, or the disjoint union of a sphere and a point.     

Theoretical and experimental correlations of gas dissolution, diffusion, and thermodynamic properties in determination of gas permeability and selectivity in supported ionic liquid membranes

Supported ionic liquid membranes (SILMs) has the potential to be a new technological platform for gas/organic vapour separation because of the unique non-volatile nature and discriminating gas dissolution properties of room temperature ionic liquids (ILs). This work starts with an examination of gas dissolution and transport properties in bulk imidazulium cation based ionic liquids [C(n)mim][NTf2] (n=2.4, 6, 8.10) from simple gas H(2), N(2), to polar CO(2), and C(2)H(6), leading to a further analysis of how gas dissolution and diffusion are influenced by molecular specific gas-SILMs interactions, reflected by differences in gas dissolution enthalpy and entropy. These effects were elucidated again during gas permeation studies by examining how changes in these properties and molecular specific interactions work together to cause deviations from conventional solution-diffusion theory and their impact on some remarkably contrasting gas perm-selectivity performance. The experimental perm-selectivity for all tested gases showed varied and contrasting deviation from the solution-diffusion, depending on specific gas-IL combinations. It transpires permeation for simpler non-polar gases (H(2), N(2)) is diffusion controlled, but strong molecular specific gas-ILs interactions led to a different permeation and selectivity performance for C(2)H(6) and CO(2). With exothermic dissolution enthalpy and large order disruptive entropy, C(2)H(6) displayed the fastest permeation rate at increased gas phase pressure in spite of its smallest diffusivity among the tested gases. The C(2)H(6) gas molecules "peg" on the side alkyl chain on the imidazulium cation at low concentration, and are well dispersed in the ionic liquids phase at high concentration. On the other hand strong CO(2)-ILs affinity resulted in a more prolonged "residence time" for the gas molecule, typified by reversed CO(2)/N(2) selectivity and slowest CO(2) transport despite CO(2) possess the highest solubility and comparable diffusivity in the ionic liquids. The unique transport and dissolution behaviour of CO(2) are further exploited by examining the residing state of CO(2) molecules in the ionic liquid phase, which leads to a hypothesis of a condensing and holding capacity of ILs towards CO(2), which provide an explanation to slower CO(2) transport through the SILMs. The pressure related exponential increase in permeations rate is also analysed which suggests a typical concentration dependent diffusion rate at high gas concentration under increased gas feed pressure. Finally the strong influence of discriminating and molecular specific gas-ILs interactions on gas perm-selectivity performance points to future specific design of ionic liquids for targeted gas separations.