Predicting thermophysical properties of biodiesel fuel blends using the SAFT-VR approach

Modeling of thermophysical properties and phase equilibria of long-chain methylesters mixtures are presented, using the SAFT-VR approach for mixtures. Molecules are represented as chains of spherical segments that can associate due to the presence of short-ranged attractive sites, using previous molecular parameters obtained for pure fatty acid methyl esters. These attractive sites as well as the intermolecular interactions between monomers segments are modeled via variable-ranged square-well potentials. The cross-energy binary-interaction parameter of the extended Berthelot combining rule was fitted to liquid densities and speed of sound. Very good predictions are obtained for isochoric heat capacities and for binary and ternary phase diagrams.     

Femtosecond to second studies of a water-soluble porphyrin derivative in chemical and biological nanocavities

The interactions of 5,10,15,20-tetrakis(4-sulfonatophenyl)-porphyrin (TSPP) with a quaternary ammonium modified β-cyclodextrin (QA-β-CD) and human serum albumin (HSA) protein in aqueous solutions at pH 7 were studied using steady-state, stopped-flow, and femtosecond to millisecond spectroscopy. TSPP forms 1:1 and 1:2 complexes with QA-β-CD (K(1) = 1.9 × 10(5) M(-1) and K(2) = 7 × 10(3) M(-1)) at 293 K, whereas with the HSA protein only 1:1 complex (K(1) = 1.7 × 10(6) M(-1)) has been found. The chemical and biological nanocavities have notable effects on the fluorescence lifetimes of the Q(x) state (from 9.3 to 11.1 ns in QA-β-CD and 11.6 ns in HSA). Furthermore, the rotational times (400 ps for the free TSPP, 1.6 and 19 ns for QA-β-CD and HSA protein complexes, respectively) clearly indicate the robustness of the formed entities. The confined environment does not affect much the fs dynamics (0.1-0.2 ps) of the encapsulated molecule. However, it clearly affect the ps one (1-2 ps (H(2)O) and 5-10 ps (QA-β-CD and HSA)). The effect of O(2) on the relaxation of the triplet state of the free and encapsulated TSPP is also studied and the obtained results are discussed in light of the shielding effect provided by the chemical and biological cavities. The observed difference, longer triplet lifetime upon encapsulation, might be relevant to the efficiency of this porphyrin in photodynamic therapy. The presteady-state kinetics of the TSPP:HSA has been studied by the stopped-flow spectrometer, and a two-step model was proposed for the complexation processes. The results show the importance of the initial association step for the overall ligand recognition process. This first step occurs with rate constant of ~4 × 10(5) M(-1) s(-1), which is about 5 orders of magnitude larger than the rate constant of the consecutive relaxation processes. We believe that our observations of molecular interaction between TSPP, QA-β-CD, and HSA protein from femtosecond to second at both ground and electronically first excited state give detailed information to improve our understanding of this kind of system and thus for a better design of drug delivery nanocarriers.     

脂肪醇物理化学性质的分子拓扑研究

借助于电负性和主量子数定义的原子结构参数为Ai,由Ai建构的新拓扑指数 ^nP=Σ（Ai·Aj·Ak……）^0.5,其中，^0P=Σ（Ai)^0.5,^1P=Σ（Ai·Aj)^0.5, ^0P与脂肪醇的摩尔折射Rm、辛醇／水分配系数IgKow,^0P及^1P与脂肪醇的摩尔磁 化率Xm、蒸发热Hv的相关系数分别为0．9947，0．9941，0．9998，0．9968，均优 于文献方法。^0P和^P与脂肪醇的气相色谱保留指数RI也具有良好的相关性，相关 系数为0．9967，^nP是一种较为理想的拓扑指数，可用于脂肪醇物理化学性质的预 测。     

Enantioselective effects in the association behaviour of optically active alcohols

The association behaviour of four optically active secondary alcohols with chiral C atoms in the α-position was investigated by means of IR spectroscopy and calorimetry CCl₄ was used as a solvent. As compared to the racemic compounds, the corresponding optically active alcohols have slightly higher concentrations of free OH groups, i.e. lower degrees of association, but somewhat higher enthalpy of association. Consequently, the H-bonding of racemic alcohols is favoured by entropy. Differences have been found also in the absorption coefficients of the associated OH groups. Optically active solvents exert some influence on the association behaviour of optically active alcohols. No differences could be observed in the H-bonding of optically active monocarboxylic acids, as compared with the racemic ones     

Imidazole-containing chitosan derivative: a new synthetic approach and sorption properties

A novel method for the synthesis of a hetaryl-containing chelate amino polymer, namely, N-(4(5)-imidazolylmethyl)chitosan (IMC), with a degree of substitution up to 0.3 was proposed. The “synthesis in gel” approach involves direct substitution of the hydroxyl group in 4(5)-imidazolylmethanol. The structures of these polymers were confirmed by ¹H NMR data. For sorption studies, IMC samples were crosslinked with epichlorohydrin and diglycidyl ethers of ethylene glycol and diethylene glycol. The degrees of swelling and sorption properties of the polymers largely depend on the crosslinking agent and the degree of crosslinking. The sorption capacities of IMC for Au^III, Pt^IV, and Pd^II ions are higher than those of the nonmodified polymer. The extraction of noble metal ions from chloride solutions becomes more selective with increasing degree of crosslinking. The sorption capacity of IMC for Co^II and Ni^II ions is higher than those of chitosan and its known N-heterocyclic derivatives.     

A new method to determine association constants for alcohols from the properties of pure compounds

Hofman, T. and Nagata, I., 1986. A new method to determine association constants for alcohols from the properties of pure compounds. Fluid Phase Equilibria, 28: 233-252.The methods used to calculate association constants and enthalpies of association from the properties of pure associated substances are critically reconsidered. A new approach is proposed for alcohols that leads to more reliable values of both enthalpies and entropies of association.     

The absolute configuration of simple aliphatic alcohols through a chemical/computational approach: triarylether derivatives of (+)-endo-2-norborneol as a case study

The reliable determination of the absolute configuration of (+)-endo-2-norborneol 1, chosen as a representative case of simple aliphatic UV–vis transparent alcohols, was obtained by transforming this compound in its 1-naphthyl-diphenylmethyl ether 5 whose ECD spectrum displays several, low-lying, intense Cotton effects, which can be satisfactorily simulated in position, sign, and intensity by TDDFT/B3LYP/6-31G¹ calculations. This result represents a possible, general, new approach to the absolute configuration of aliphatic alcohols.     

Identification of a novel protein regulating microtubule stability through a chemical approach

To identify novel proteins regulating the microtubule cytoskeleton, we screened a library of purine derivatives using mitotic spindle assembly in Xenopus egg extracts as an assay. Out of a collection of 1561 compounds, we identified 15 that destabilized microtubules without targeting tubulin directly, resulting in small spindles. Affinity chromatography with one compound, named diminutol, revealed a potential target as NQO1, an NADP-dependent oxidoreductase. A role for NQO1 in influencing microtubule polymerization was confirmed through inhibition studies using known inhibitors and immunodepletion. Therefore, this chemical approach has identified a novel factor required for microtubule morphogenesis and cell division.     

Steric and electronic contributions to conformational effects on chemical shifts of acyclic alcohols

Our calculations on bi- and polycyclic alcohols reveal that the Mulliken charge distribution and chemical shift patterns due to hyperconjugation of lone pairs on oxygen with neighboring groups break down or are attenuated for certain spatial relationships of the hydroxyl group. Since in strained ring systems other effects on these parameters may be present, we applied a similar analysis to acyclic alcohols. Calculations at the B3LYP/6-31G^* level on conformers of methanol, ethanol, 1- and 2-propanol, 2-methyl-1-propanol, 2-methyl-2-propanol, 2-butanol, 2-methyl-2-butanol, 1- 2- and 3-pentanol and 2-methyl-3-pentanol, where hyperconjugation may be present, reveal steric effects as modifiers of hyperconjugative patterns affecting carbon-13 chemical shifts in such alcohols. Contrary to what is observed in bi- and policyclic systems, where electrostatic effects interfere with effects due to hyperconjugation, these steric effects may be the main cause for the attenuation of deshielding of nuclei that are subject to hyperconjugation. Electrostatic effects are also present but they do not interfere with hyperconjugation by lone pairs. Conformational effects fall off sharply after the third carbon in the chain.     

Computational description of quantum chemical calculations and pharmacological studies of the synthesized chalcone derivative: A promising NLO material

The intended chalcone, (E)-1-(4-aminophenyl)-3-(4-ethoxyphenyl)-prop-2-en-1-one (4A3EP), was synthesized in an alkaline medium by the Claisen–Schmidt condensation reaction of 4-aminoacetophenone with 4-ethoxybenzaldehyde. Spectroscopic analytical techniques such as UV–visible, FT-IR, FT-RAMAN, ¹H NMR, and ¹³C NMR investigations were used to analyze the molecular structure of the title molecule. The optimized molecular structure of the chalcone in gas phase vibrational frequencies and associated vibrational assignments were theoretically studied and compared with experimental results using the B3LYP/6–311++G techniques. All the experimental results were found to be in line with the theoretical values. The non linear optical activity of the title compound was proved from the hyperpolarizability calculations. In addition, E_HOMO (?5.9038 eV), E_LUMO (?2.2833 eV), energy gap (3.6205 eV) and electrophilicity index (4.628) were calculated to explore the reactivity, stability and bio activity of the title compound. The molecular electrostatic potential map was generated in order to spot the electrophilic and nucleophilic sites in the title compound. Natural bond orbital analysis was investigated in order to forecast the stability and charge transfer tendency of a title molecule. FUKUI FUNCTIONS were also calculated using DFT. Its anti-inflammatory, anti-diabetic, and anti-oxidant activities were also investigated. A molecular docking model was used to study the ligand-protein binding interactions of a synthetic chalcone derivative with the main protease of SARS-CoV-2 (the PDB code is 6yb7).     

Investigation of the association of higher fatty alcohols on a chromatographic paper

Summary An attempt was made to apply a low-activity chromatographic layer (Whatman 2) and a non-polar mobile phase (decalin) in studying the self-association of higher fatty alcohols. The obtained results showed a satisfactory, semi-quantitative agreement with IR spectroscopic data and theoretical considerations and calculations. Usefulness of the complementary paper chromatographic investigations can be considered as complementary investigations when setudying the self-association of higher fatty alcohols.     

A comprehensive electronic structure description of a biscyanotetraazacobalt(III) macrocyclic complex

Molecular modeling and a detailed spectroscopic characterization of the macrocyclic complex [Co(meso)(CN)(2)](+) (meso = 5,5,7,12,12,14-hexamethyl-1,4,8,11-tetraazacyclotetradecane) is herein presented. Structural, electronic and vibrational features are discussed and assignments were proposed on the basis of semi-empirical (molecular mechanics (MM+), ZINDO/S and PM3) quantum-mechanics calculations. The energy and the composition of the molecular orbitals of the complex were calculated and a quantitative diagram was constructed. The simulated UV-vis spectrum exhibited a reasonably good accordance with the experimental one and fully assignments of seven bands were made. An optimized configuration of the complex showed a strong cobalt-cyanide axial bond in agreement with the major contribution of the cyanide to the composition of the molecular orbitals in contrast to a discrete participation of the macrocyclic meso to the ground state of the complex.     

A simple approach to separate a mixture of homopropargylic and allenic alcohols

A simple and practical approach to separate homopropargylic alcohol from allenic alcohol has been developed. It involves the formation of an insoluble silver acetylide species between silver nitrate and homopropargylic alcohol in aqueous acetone which can be separated from the allenic alcohol through a simple filtration. The homopropargylic alcohol can subsequently be recovered by hydrolysis with 1 N HCl. This protocol has been applied to the separation of a mixture of chiral homopropargylic and allenic alcohols in excellent yields with retention of absolute stereochemistry.     

Cyclodextrin effects on physical–chemical properties of novocaine

The UV-vis absorption and the fluorescence emission spectra of novocaine were analysed in aqueous cyclodextrin (CD) solutions. Either the absorbance read at λ_max 290 nm or the fluorescence emission intensity at λ_ems 346 nm increase in the presence of both α- and β-CD due to the formation of 1:1 inclusion complexes. The lower polarity of the CD-cavity sensed by the included drug enhances the emitted fluorescence; in fact, the same effect was observed in aqueous mixtures of acetonitrile, dioxane, or dimethylsulfoxide. The inclusion complex formation between the monocation of novocaine and CDs diminishes the electrical conductance of aqueous solutions of novocaine hydrochloride (NoHCl). Both the nitrosation reaction in aqueous acid medium and the ester hydrolysis in alkaline medium are retarded in the presence of CDs. The strongest effect was observed with β-CD as a consequence of the higher stability inclusion complex.     

A novel asymmetric approach to a densely functionalized lactarane ring system through a domino ring opening-ring closing metathesis of a norbornene derivative

A novel route for the synthesis of a highly functionalized lactarane skeleton in enantiomerically pure form is described via ROM-RCM of an appropriately constructed norbornene derivative as the key step.     

A new approach to 2,2-disubstituted chromenes and tetrahydroquinolines through intramolecular cyclization of chiral 3,4-epoxy alcohols

An efficient route to chiral chromene and tetrahydroquinoline ring models 3 and 4 was developed by means of the vanadium epoxidation of chiral homoallylic alcohols 12 and 19 followed by an intramolecular epoxide opening of 3,4-epoxy alcohols 14 and 20. The configuration of all compounds was confirmed using NMR analysis.     

On the effects of ion-wall chemical association on the electric double layer: a density functional approach for the restricted primitive model at a charged wall

We describe a density functional theory for the restricted primitive model of ionic fluid at a charged wall with active sites to which ions can bond. The theory is an extension of our recent approach [Pizio et al., J. Chem. Phys. 121, 11957 (2004)] and is focused in the effects of specific adsorption of ions on the wall, besides the electrostatic phenomena. In order to solve the problem, we use the first-order thermodynamic perturbation theory of chemical association developed by Wertheim [J. Chem. Phys. 87, 7323 (1987)]. The microscopic structure of the electric double layer and the amount of adsorbed charge are investigated. Also, the temperature dependence of capacitance is analyzed. The capacitance depends on the kind of ions that form associative bonds with the surface sites and is determined by a net charge acting on the diffuse layer. The shape of the temperature dependence of capacitance essentially depends on the association energy and the density of bonding sites.     

芘衍生物发光行为的研究

本工作合成了新型的芘衍生物-芘基查尔酮(PD), 研究了其在溶液及胶束中的稳态光物理行为。结果表明: 即使在较低浓度条件下, PD分子间也容易生成基态电荷转移配合物(Inter-CT), 其荧光光谱表现为芘单体荧光、分子内电荷转移态(Intra-CT)荧光以及Inter-CT荧光, 并且具有较好的溶致变色效应、浓度效应以及温度效应, 是一良好的探针分子化合物。