Synthesis of a Highly Aromatic and Planar [10]Annulene

As the next neutral structure following Hückels rule, a planar and aromatic [10]annulene is ideal to study the link between ring size and aromaticity. However, the puckered geometry of the parent [10]annulene suggests that the aromatic stabilization energy is not sufficient to overcome the ring strain that exists when the system is forced into planarity. It has been shown computationally that this ring strain can be alleviated through the addition of two or more cyclopropane rings to the periphery, thereby creating theoretically aromatic structures. An alternative strategy to eliminating the issue of ring strain was demonstrated experimentally with the successful preparation of the highly aromatic 1,6-didehydro[10]annulene. However, the system rapidly cyclizes at -40°C to a naphthalene diradical due to the close proximity of the in-plane p-orbitals present in the system. Here we show that cyclopropanating one side of the unstable annulene successfully prevents the destabilizing cross-ring interaction while maintaining a highly aromatic structure. Remarkably, the formed [10]annulene is bench stable and can be stored for extended periods of time.<br>

Synthesis of a Highly Aromatic and Planar [10]Annulene

As the next neutral structure following Hückels rule, a planar and aromatic [10]annulene is ideal to study the link between ring size and aromaticity. However, the puckered geometry of the parent [10]annulene suggests that the aromatic stabilization energy is not sufficient to overcome the ring strain that exists when the system is forced into planarity. It has been shown computationally that this ring strain can be alleviated through the addition of two or more cyclopropane rings to the periphery, thereby creating theoretically aromatic structures. An alternative strategy to eliminating the issue of ring strain was demonstrated experimentally with the successful preparation of the highly aromatic 1,6-didehydro[10]annulene. However, the system rapidly cyclizes at -40°C to a naphthalene diradical due to the close proximity of the in-plane p-orbitals present in the system. Here we show that cyclopropanating one side of the unstable annulene successfully prevents the destabilizing cross-ring interaction while maintaining a highly aromatic structure. Remarkably, the formed [10]annulene is bench stable and can be stored for extended periods of time.<br>

The basis of a more contagious 501Y.V1 variant of SARS-COV-2

Severe acute respiratory syndrome-related coronavirus 2 (SARS-CoV-2) is causing a world-wide pandemic. A variant of SARS-COV-2 (20I/501Y.V1) recently discovered in the United Kingdom has a single mutation from N501 to Y501 within the receptor binding domain (Y501-RBD), of the Spike protein of the virus. This variant is much more contagious than the original version (N501-RBD). We found that this mutated version of RBD binds to human Angiotensin Converting Enzyme 2 (ACE2) a ~10 times more tightly than the native version (N501-RBD). Modeling analysis showed that the N501Y mutation would allow a potential aromatic ring-ring interaction and an additional hydrogen bond between the RBD and ACE2. However, sera from individuals immunized with the Pfizer-BioNTech vaccine still efficiently block the binding of Y501-RBD to ACE2 though with a slight compromised manner by comparison with their ability to inhibit binding to ACE2 of N501-RBD. This may raise the concern whether therapeutic anti-RBD antibodies used to treat COVID-19 patients are still efficacious. Nevertheless, a therapeutic antibody, Bamlanivimab, still binds to the Y501-RBD as efficiently as its binds to N501-RBD.

Crystallographic and spectroscopic characterization of 2-[(7-acetyl-4-cyano-6-hydroxy-1,6-dimethyl-8-phenyl-5,6,7,8-tetrahydroisoquinolin-3-yl)sulfanyl]-N-phenylacetamide

In the title molecule, C28H27N3O3S, the heterocyclic portion of the tetrahydroisoquinoline unit is planar and an intramolecular N—H...N hydrogen bond and a C—H...π(ring) interaction help to determine the overall conformation. In the crystal, a layer structure with the layers parallel to (10\overline{1}) is generated by O—H...O and C—H...O hydrogen bonds.

Crystal structure of 2-hydroxy-2-phenylacetophenone oxime

The title compound [systematic name: 2-(N-hydroxyimino)-1,2-diphenylethanol], C14H13NO2, consists of hydroxy phenylacetophenone and oxime units, in which the phenyl rings are oriented at a dihedral angle of 80.54 (7)°. In the crystal, intermolecular O—HOxm...NOxm, O—HHydr...OHydr, O—H′Hydr...OHydr and O—HOxm...OHydr hydrogen bonds link the molecules into infinite chains along the c-axis direction. π–π contacts between inversion-related of the phenyl ring adjacent to the oxime group have a centroid–centroid separation of 3.904 (3) Å and a weak C—H...π(ring) interaction is also observed. A Hirshfeld surface analysis of the crystal structure indicates that the most important contributions for the crystal packing are from H...H (58.4%) and H...C/C...H (26.4%) contacts. Hydrogen bonding and van der Waals contacts are the dominant interactions in the crystal packing.

Cavitation shapes measurements in piston-ring lubrication and their link to lubricant properties

The emissions control regulations introduced by governments are set to improve engine quality and reduce the impact automobiles have on the planet. The regulations imposed on the manufactures have proven very difficult to meet. To this effect some of the leading names in the industry were pushed to invest significant funding in research, development and optimisation of combustion, powertrain and tribology inside the ICE. Their goal is reduction of fuel consumption and emissions while increasing performance and durability. The piston-ring and cylinder-liner interaction is the major source of frictional losses for reciprocating ICEs and so, it is important to avoid any failure of piston-rings to effectively control lubricant transport from the sump onto the cylinder walls and further to the combustion chamber. This lubricant will participate in the emissions through absorption and desorption of fuel in the oil film at the cylinder walls, also resulting in lubricant contamination and consumption. The objective of this project is to assist with the investigation of phenomena occurring in the cylinder liner and piston-ring interaction under different operating conditions. The following investigations have been carried out, flow and cavitation visualisation in a model lubricant rig and cavitation visualisation in a newly designed optical engine.

Experimental and computational evidence for a stabilising C–Cl(lone-pair)⋯π(chelate-ring) interaction

Stabilising C–Cl(lone-pair)⋯π(chelate ring) interactions are described.

Numerical study on thoracic aortic aneurysms : the aneurysms aggravation effects on the seconda rythme flows motion

It is Well know that there is a strong correlation between artery wall diseases and the flow structure disturbance. Aneurysms are enlargements situated at different but specifics parts of the vascular system; it is a silent diseas that evolves in time. The thoracic aortic aneurysms (T. A. A) remains relatively unstudied and therefore the present study aimis is to clarify the effects of the (T . A. A) evolution and the geometrical variations on both hydrodynamic instabilities inside the aortic bulge especially the vortex ring phenomenon and the secondary motion (Dean and lyne vortices) downsream the aneurysms. Two different cases of asymmetric enlargements in the ascending part of the aortic are studied for both newtonien and the shear-thinning model to mimic the blood rheology inside the aneurysms bulge in order to investigate both parameters impact on the vortex ring behavior. Results schowed that the blood rheoligy effects the propagation velocity while the aneurysms size influences the vortex ring rupture, the motion of the ring interaction with an inclined wall phenomenon. Results also showed that vortex ring disturbs the boundary layer and therefore the secondary motion in the rest of the aorta.