Solubility evolution of elemental sulfur in natural gas with a varying H2S content.

CONTEXT: The solubility variations of elemental sulfur are of great importance in the prevention of sulfur deposition during the development of high-sulfur gas formations. It has been observed that the solubility varies with H2S content, which is the main solvent of elemental sulfur in natural gas. Moreover, the addition of small amounts of CH4 and/or CO2 in H2S leads to a dramatic solubility reduction of which the mechanism remains unclear. Using a modified direct coexistence method, molecular dynamics simulations are conducted to uncover the molecular mechanism of the solubility reduction. The observed solubility variations with H2S content are reproduced, and the solubility reduction is interpreted by the antisolvent effect of CH4 and CO2. While the H2S content varies in a wide range in the known high-sulfur gas formation, our simulations provide useful information for controlling the sulfur deposition in gas development. METHODS: Molecular dynamics simulations are carried out using the LAMMPS package. The initial models are constructed with the Packmol software. The Ballone and Jones' potential is used for S8, the Galliero's potential for H2S and CO2, and the transferable potentials for phase equilibria-united atom (TraPPE-UA) force field for CH4. The time step is set to 1 fs, and the molecular trajectories of additional 2 ns after equilibrium are collected for analysis.

Silyl Radical Generation from Silylboronic Pinacol Esters through Substitution with Aminyl Radicals.

A novel strategy was developed to generate silyl radicals from silylboronic pinacol esters (SPEs) through nucleohomolytic substitution of boron with aminyl radicals. We successfully applied this strategy to obtain diverse organosilicon compounds using SPEs and N-nitrosamines under photoirradiation without any catalyst. The ability to access silyl radicals offers a new perspective for chemists to rapidly construct Si-X bonds.

Design, synthesis, in vitro and in vivo anti-respiratory syncytial virus (RSV) activity of novel oxizine fused benzimidazole derivatives.

Respiratory syncytial virus (RSV) causes serious lower respiratory tract infections. Currently, the only clinical anti-RSV drug is ribavirin, but ribavirin has serious toxic side effect and can only be used by critically ill patients. A series of benzimidazole derivatives were synthesized starting from 1,4:3,6-dianhydro-d-fructose and a variety of o-phenylenediamines. Evaluation of their antiviral activity showed that compound a27 had the highest antiviral activity with a half maximal effective concentration (EC50) of 9.49 µM. Investigation of the antiviral mechanism of compound a27 indicated that it can inhibit the replication of RSV by inhibiting apoptosis and autophagy pathways. Retinoic acid-inducible gene (RIG)-I, TNF receptor associated factor (TRAF)-3, TANK binding kinase (TBK)-1, interferon regulatory factor (IRF)-3, nuclear factor Kappa-B (NF-κB), interferon (IFN)-ß, Toll-like receptor (TLR)-3, interleukin (IL)-6 were suppressed at the cellular level. Mouse lung tissue was subjected to hematoxylin and eosin (HE) staining and immunohistochemistry, which showed that RSV antigen and M gene expression could be reduced by compound a27. Decreased expression of RIG-I, IRF-3, IFN-ß, TLR-3, IL-6, interleukin (IL)-8, interleukin (IL)-10, inducible nitric oxide synthase (iNOS) and tumor necrosis factor (TNF)-α was also found in vivo.

Semisynthesis of CRV431.

The non-immune-suppressive cyclophilin inhibitor CRV431 is a clinical candidate to cure nonalcoholic steatohepatitis (NASH) and has the potential to treat liver fibrosis and cancer incidence. Herein we report a concise chemical semisynthesis of CRV431 in four steps from the commercially available cyclosporine, featuring in this the flow-chemistry-based methylenation an intermolecular ring-closing metathesis and a Rh-catalyzed diastereoselective hydrogenation.

Highly enhanced nonlinear optical absorption with ultrafast charge transfer of reduced graphene oxide hybridized by an azobenzene derivative.

Graphene-based materials have been attracted many attentions due to their excellent properties and potential applications in many fields. Graphene also provides a flexible substrate to develop novel functional materials by hybridizing with other organic or inorganic components. Herein, we report the functionalization of reduced graphene oxide (RGO) with an azobenzene derivative (BNB-t8) containing the π-conjugated moiety and hydrogen bonding groups, to improve the optical and nonlinear optical properties of RGO. With the introducing of BNB-t8, a new absorption band is formed and dominates the absorption spectrum, clearly demonstrates that the BNB-t8 has been hybridized with RGO, by combining the analysis of Raman and XRD data. Femtosecond Z-scan results present a highly enhanced saturable optical absorption of BNB-t8/RGO hybrid compared with that of RGO. By optimizing the hybridization ratio of BNB-t8 to RGO, the saturable absorption coefficient of BNB-t8/RGO hybrid reaches to -237 m/W, 38 times larger than that of RGO (-6.2 m/W). In the meantime, the third-order susceptibility χ(3) of BNB-t8/RGO hybrid is aslo enhanced by 8 times to be 5.18×10-13 esu. These enhancements of nonlinear optical properties of BNB-t8/RGO hybrid mainly arise from the charge transfer from RGO to BNB-t8. Femtosecond transient absorption measurements reveal that the charge separation takes place in 0.28 ps and the charge recombination in 2.0 ps, indicating a strong electron coupling and thus an enhanced electron delocalization in BNB-t8/RGO hybrid compared with those in RGO. We suggest that the noncovalent π-π interaction plays the dominant role for enhancing the electron delocalization of RGO after hybridizing with BNB-t8, while the hydrogen bonding interaction reinforce the coupling interaction between BNB-t8 and RGO moieties in the hybrid. The as-prepared BNB-t8/RGO hybrid with high saturable absorption coefficient with an ultrafast response presents a potential candidate as saturable absorber of mode-locked laser.