Database Survey of Single-and-Half Phosphorus–Oxygen Bonds in Salts with the C2PO2 Segment: Crystal Structure of [NH2C5H4NH][(C6H5)2P(O)(O)]⋅2H2O

Crystallography Reports - For structures with a C2PO2 skeleton, a comparison of “single-and-half” phosphorus–oxygen bonds with single and double phosphorus–oxygen bonds is...     

Two single‐enantiomer amidophosphoesters: a database study on the chirality of (O)2P(O)(N)‐based structures

The crystal structures of two single‐enantiomer amidophosphoesters with an (O)₂P(O)(N) skeleton, i.e. diphenyl [(R)‐(+)‐α‐methylbenzylamido]phosphate, (I), and diphenyl [(S)‐(?)‐α‐methylbenzylamido]phosphate, (II), both C₂₀H₂₀NO₃P, are reported. In both structures, chiral one‐dimensional hydrogen‐bonded architectures, along [010], are mediated by N—H…OP interactions. The statistically identical assemblies include the noncentrosymmetric graph‐set motif C(4) and the compounds crystallize in the chiral space group P2₁. As a result of synergistic co‐operation from C—H…O interactions, a two‐dimensional superstructure is built including a noncentrosymmetric R₄⁴(22) hydrogen‐bonded motif. A Cambridge Structural Database survey was performed on (O)₂P(O)(N)‐based structures in order to review the frequency of space groups observed in this family of compounds; the hydrogen‐bond motifs in structures with chiral space groups and the types of groups inducing chirality are discussed. The ^2,3J_X–P (X = H or C) coupling constants from the NMR spectra of (I) and (II) have been studied. In each compound, the two diastereotopic C₆H₅O groups are different, which is reflected in the different chemical shifts and some coupling constants.     

The Zero-Divisor Graph Associated to a Semigroup

The zero-divisor graph of a commutative semigroup with zero is the graph whose vertices are the nonzero zero-divisors of the semigroup, with two distinct vertices adjacent if the product of the corresponding elements is zero. New criteria to identify zero-divisor graphs are derived using both graph-theoretic and algebraic methods. We find the lowest bound on the number of edges necessary to guarantee a graph is a zero-divisor graph. In addition, the removal or addition of vertices to a zero-divisor graph is investigated by using equivalence relations and quotient sets. We also prove necessary and sufficient conditions for determining when regular graphs and complete graphs with more than two triangles attached are zero-divisor graphs. Lastly, we classify several graph structures that satisfy all known necessary conditions but are not zero-divisor graphs.     

Nonequilibrium versus equilibrium molecular dynamics for calculating the thermal conductivity of nanofluids

Journal of Thermal Analysis and Calorimetry - Both equilibrium and nonequilibrium molecular dynamics (EMD and NEMD, respectively) methods have been used to predict the thermal conductivity of...     

Preparation of ceramic γ-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-TiO<Subscript>2</Subscript> nanofiltration membranes for desalination

As one of the most recently developed membrane separation processes, nanofiltration (NF) has found a number of industrial applications. Ceramic NF membranes are also regarded as the appropriate choice in many applications, due to their higher chemical and physical stability. In this study, the rejection of the chloride ion is investigated using bi-layered γ-Al₂O₃-TiO₂ NF membranes based on α-alumina supports. Compression is used in preparation of the supports and sol-gel dip-coating for the top-layer formation. SEM micrographs, XRD, and nitrogen adsorption/desorption isotherms are used for membrane characterisation. The results show that the calcination temperature (600°C) results in different crystal structures including the brookite phase of TiO₂, the γ phase of Al₂O₃, and a combined phase of aluminium-titanium oxides. The average pore size of the membrane was identified as 1.6 nm using an adsorption/desorption isotherm. The rejection was also studied for the chloride ion, using a cross-flow filtration module. Filtration tests were carried out under different pressures, pH values, and salt concentrations; these showed a smoother behaviour particularly around the isoelectric points (IEPs) due to the dual-layer structure, with the best rejection at pH of approximately 5.     

Wettability alteration of carbonate rocks from strongly liquid-wetting to strongly gas-wetting by fluorine-doped silica coated by fluorosilane

Wettability alteration is an important mechanism to increase recovery from oil and gas reservoirs. In this study, effect of fluorine-doped silica coated by fluorosilane nanofluid on wettability alteration of carbonate rock was investigated. The nanoparticle synthesized by sol-gel method was characterized using XRD, FTIR, SEM, and DLS. Adsorption of nanoparticle on rock was characterized by FESEM, and composition of rock after treatment was determined by EDXA. Effect of nanofluid on wettability was investigated by measuring static, advancing, and receding contact angle and surface free energy, imbibition of water, crude oil, and condensate of untreated and treated carbonate rock. Also, stability of contact angle and thermal stability of nanofluid were studied. ?Results show that contact angles for water, condensate, and crude oil were altered from 37.95°, 0°, ?and 0° to 146.47°, 145.59°, and 138.24°. In addition, water, condensate, and oil imbibition ?decreased more than 87, 88, and 80%, indicating that wettability was altered from strongly oil wet, ?condensate wet, and water wet to strongly gas wet. The ultraoleophobic and ultrahydrophobic stability were >48 hours and 120 minutes. Surface free energy of treated rock for water, crude oil, and condensate was ?2.24, 1.17, and 1.47mN/m. Thermal stability of nanofluids and adsorbed nanoparticle was up to 150°C.     

Synthesis, Spectroscopic Characterization and Crystal Structure of a New Acetyl phosphorylamidate P(O)[NHC(O)C6H4(4-NO2)][N(CH(CH3)2)(CH2C6H5)]2

Abstract  

A new acetyl phosphorylamidate P(O)[NHC(O)C₆H₄(4-NO₂)][N(CH(CH₃)₂)(CH₂C₆H₅)]₂ has been synthesized and characterized by elemental analysis, ¹H, ¹³C and ³¹P NMR, IR and single crystal X-ray diffraction. Single crystal X-ray analysis shows that it belongs to triclinic system, space group P[`1] P\bar{1} , with a = 10.5868(16) Å, b = 11.8058(18) Å, c = 12.4364(19) Å, α = 65.410(3)°, β = 67.492(4)°, γ = 85.879(3)°, V = 1,298.6(3) Å³, and Z = 2. The intermolecular PO···HN hydrogen bond makes H-bonded dimer of molecule with Ci symmetry. In the crystal network, the dimers are aggregated in the chain arrays through π-stacking between p-NO₂–C₆H₄–C(O)–NH– moieties. Moreover, weak C–H···O and C–H···π interactions exist in the crystal network.