Chiral ionic liquid-mediated photochirogenesis. Enantiodifferentiating photocyclodimerization of 2-anthracenecarboxylic acid

Enantiodifferentiating photocyclodimerization of 2-anthracenecarboxylic acid (AC-H) and its lithium salt (AC-Li) in chiral ionic liquid (CIL), (R)-1-(2,3-dihydroxypropyl)-3-methylimidazolium acetate {[(R)-GLYMI][AcO]}, gave a mixture of two head-to-tail (HT) and two head-to-head (HH) cyclodimers in HT/HH ratios of 1.3-1.7 (for AC-H) and 2.2-4.3 (for AC-Li) with low enantiomeric excesses (ee) of 0-3% for chiral syn-HT and anti-HH dimers. In contrast, irradiation of AC-H in an aqueous solution, containing cucurbit[8]uril (CB[8]) as a host and [(R)-GLYMI][AcO] or [(R)-GLYMI][Tf(2)N] as a modifier of CB portals, afforded the HH dimers in 91-99% selectivity, although the anti-HH dimer was totally racemic. Interestingly, irradiation of AC-H in a dichloromethane solution, containing [(R)-GLYMI][AcO] as a chiral template, led to the formation of the HH-dimers in 98% selectivity with chiral anti-HH dimer in -14% ee, presumably by the dual ligation of two ACs to a CIL through electrostatic and hydrogen-bonding interactions.     

HR MAS NMR, powder XRD and Raman spectroscopy study of inclusion phenomena in ��CD nanosponges

Three different samples of ?? cyclodextrin nanosponges (CDNS) are prepared from ?? cyclodextrin (??CD) and pyromellitic dianhydride (PMA). CDNS are cross-linked, nanoporous materials whose pore size can be modulated by suitable choice of the CD/PMA molar ratio. In the presence of aqueous solutions they can swell giving rise to gel-like behavior. The Raman spectra of dry and water treated CDNS are described, with emphasis on the group vibration modes in the low frequency part of spectrum, sensitive to molecular environment and cross-linking degree, and on O?CH/C?CH vibration modes of dry/swollen CDNS, in turn providing information on the hydration dynamics. Powder X-ray diffraction data indicate low crystallinity and the presence of bulk water within the 3D polymer network. High resolution magic angle spinning (HR MAS) NMR spectroscopy is successfully used for investigation of swollen CDNS. The NMR signals of bulk and ??bound?? water indicate two different states of water molecules inside the gel. Probe solute fluorescein is used to spot on the diffusion properties inside the gel. In one case the diffusion coefficient of fluorescein measured in CDNS results one order of magnitude higher than that in D₂O. The acceleration effect uncovered indicates that the motion of fluorescein inside the porous gel is driven by both hydrodynamic and electrostatic factors.     

Possibility of Solitions with Charge ± e/2 in Highily Correlated 1:2 Salts of Tetracyanoqutnodimethane (TCNQ)

Solitons with fractional charge ± e/2 might be experimentally realized in the highly correlated 1:2 salts of TCNQ if the quarter filled TCNQ chains of these compounds correspond to linear Hubbard chanins dominated by the on-site Coulomb repulsion. The low-teperature current carrying excitations of the TCNQ chains would consist of thermally activated pairs of such fractionally charged solitons. The addition of a single electron to a TCNQ chain would lead to the formation of two identical solitons with half-integer charge.     

Bio-based benzoxazines synthesized in a deep eutectic solvent: A greener approach toward vesicular nanosystems

A green synthesis of benzoxazines, based upon reaction of cardanol with formaldehyde and primary amines, is achieved in high yields using choline chloride-urea mixture as deep eutectic solvent. Then, it is demonstrated how the cardanol-based benxoxazines can be employed as only component for the preparation of a nanovesicular systems.     

Plasticizer for poly(vinyl chloride) from cardanol as a renewable resource material

The present work is aimed to the preliminary analysis of the applicability of cardanol derivatives as renewable plasticizers for soft PVC. Two different plasticizers were studied, obtained by esterification of the cardanol hydroxyl group (cardanol acetate) and further epoxidation of the side chain double bonds (epoxidated cardanol acetate). Differential Scanning Calorimetry (DSC) was used to study the miscibility between PVC and cardanol derived plasticizers. The miscibility was correlated to the chemical structure of plasticizer by means of the Hansen solubility parameter analysis. Results obtained indicated that esterification of cardanol yields a partial miscibility with PVC, whereas esterification and subsequent epoxidation yield a complete miscibility with PVC. Therefore cardanol acetate, obtained by solvent-free esterification of cardanol, was used as a secondary plasticizer of PVC. Mechanical and rheological analysis showed that the cardanol acetate can partially replace DEHP in PVC formulation.     

Robotically controlled scale-model testing of masonry vault collapse

Scale-model testing can be used to understand the equilibrium and validate the computational modelling of discrete-element assemblies subjected to external loads or support displacements. This paper proposes a novel approach to investigate the collapse of discrete-element assemblies using 3D-printed scale models manipulated with force-sensitive robotic arms combined with an optical measuring system. To demonstrate that this provides a more flexible and comprehensive solution for the assessment of the structural behaviour of unreinforced masonry structures, the same setup is used to conduct different types of experiments on a 3D-printed model of a cross vault. First, the robotic arms are used to apply a point load in different locations while measuring the resistance of the vault until collapse. In a second experiment, the robotic arms are used to simulate the effect of progressive differential settlement of the supports of the vault. The trajectory along which the displacement of the support is applied is based on real-time measurements by the force-sensitive robots of the occurring outward thrust.     

Thermal dimerization of 1,3-butadiene: Kinetics of the formation of cis,cis-cycloocta-1,5-diene

The thermal reaction of 1,3-butadiene (BD) has been studied between 464 and 557°K at pressures between 49 and 450 torr. The products are 4-vinylcyclohexene (VCH) and cis, cis-cycloocta-1,5-diene (COD), and their formations are second order. The rate constant (in 1/mol · sec) for VCH is given by and that for COD by The thermal reaction of COD has also been studied. The temperature was varied from 505 to 586°K and the pressure from 15 to 51 torr. The rate constants (in sec^?1) for the formations of VCH and BD are given by A biradical mechanism seems to fit these results. The heat of formation and the entropy of COD are estimated.