Substituent effect on geometric and electronic structure of benzenesulfonic acid: gas-phase electron diffraction and quantum chemical studies of 4-CH3C6H4SO3H and 3-NO2C6H4SO3H molecules

A combined gas-phase electron diffraction/mass-spectrometric and quantum chemical (B3LYP/cc-pVTZ, MP2/cc-pVTZ) study of the molecular structures of para-methylbenzenesulfonic acid (4-MBSA) and meta-nitrobenzenesulfonic acid (3-NBSA) was carried out. On the basis of mass spectrometric analysis, it was found that the substituted benzenesulfonic acids are thermostable at least up to 431(3) K. The fragmentations of 4-MBSA and 3-NBSA molecules under electron impact were analyzed. Quantum chemical calculations show that the 4-MBSA molecule exists as an enantiomeric pair, which is formed as a result of rotation of OH group about the S–O(H) bond. The 3-NBSA molecule has two conformers with different orientations of the O–H bond with respect to the nitro group and two corresponding enantiomers. The equilibrium configurations of 4-MBSA and both conformers of 3-NBSA have similar structures of the SO₃H group, with the O–H bond eclipsing one of the S=O bonds. Selected experimental bond distances for 4-MBSA/3-NBSA are (Å) r _h1(C–C)_av = 1.403(3)/1.395(4); r _h1(C–S) = 1.765(5)/1.784(5); r _h1(S=O)_av = 1.433(4)/1.438(4); and r _h1(S–O) = 1.618(4)/1.620(4). The potential functions for the internal rotation of SO₃H, OH, and CH₃ or NO₂ groups were calculated, and the transition states between enantiomers (conformers) were determined. The influence of substituent's nature on molecular geometry as well as on the energies of frontier orbitals and red-ox properties of the compounds is discussed. The inductive and mesomeric substituent effects were estimated from the donor–acceptor interaction energies of the natural bond orbitals of substituent and benzene frame. The correlation between group electronegativities and cooperative energetic characteristics of inductive and mesomeric effects of substituents is shown.     

Reductive electrochemical formation of 6H-dibenzo[b,d]pyran-6-one and 2-benzopyran-1(1H)-one

In the present Letter several carbolactones (oxidative products) are obtained under aprotic cathodic conditions in the preparative scaled electrolysis of 1,2-quinones in a divided electrochemical cell and in the presence of oxygen. When 9,10-phenanthrenequinone is reduced 6H-dibenzo[b,d]pyran-6-one and [1,1′-biphenyl]-2,2′-dicarboxylic acid are obtained as major products. In the reduction of 1,2-naphthoquinone, 2-benzopyran-1(1H)-one, and 2-(2-carboxyethenyl)-benzoic acid were formed as main products. The proposed mechanism to explain the formation of these and other products, that involves an electron-transfer reaction to the oxygen in air, is now discussed.     

Kinetics and mechanism of oxygen electroreduction on Vulcan XC72R carbon black modified by pyrolysis products of cobalt 5,10,15,20-tetrakis(4-methoxyphenyl)porphyrine in a broad pH interval

The kinetic parameters of oxygen reduction reaction on Vulcan XC72R carbon black, carbon black modified by pyrolysis products of cobalt 5,10,15,20-tetrakis(4-methoxyphenyl)porphyrine named by MXC72R, and commercial Pt/C platinum catalyst have been considered. Comparison of their electrochemical properties including pH influence in a broad interval from 0.3 to 14.6 has shown platinum-similar behavior of MXC72R in the reaction under study. An increasing order of electrochemical activity for oxygen reduction reaction is obtained, namely XC72R?<?MXC72R?<?Pt/C. The mechanism of oxygen reduction reaction is discussed emphasizing the important accelerating role of protonation of adsorbed oxygen molecule and inhibiting role of oxygen-containing species (formed due to water molecule discharge) and strongly adsorbed foreign species. The importance of the research on oxygen reduction reaction in a broad pH interval to evaluate the efficiency of various precious metal-free catalytic systems in comparison to platinum is emphasized.     

On the response of semitransparent nanoparticulated films of LuPO<Subscript>4</Subscript>:Eu in poly-energetic X-ray imaging applications

In the present work, we demonstrate the fabrication technique of highly translucent layers of nanoparticulated (~50 nm) LuPO₄:Eu phosphor, present their basic luminescent properties and give results of their performance in a planar imaging system coupled to a CMOS photodetector. For comparison, the imaging performance of an opaque Gd₂O₂S:Eu phosphor screen prepared by sedimentation is also shown. The X-ray detection parameters as well as the luminescence efficiency of the investigated films were discussed. Results show that the in-line transmittance at ~600–700 nm, in the range of the phosphor luminescence, varies with respect to the thickness of the films from 40 to 50 % for a film of 67 μm thick to 4–12 % when the thickness increases to 460 μm. Yet, X-ray detection parameters get enhanced as the thickness of the films increases. Those results affect the luminescence efficiency curves of the films under poly-energetic X-ray radiation of various tube energies. The normalized noise power spectrum values were found similar for LuPO₄:Eu films and a phosphor screen made using commercial Gd₂O₂S:Eu powder. The detective quantum efficiency of our films is clearly lower compared to the Gd₂O₂S:Eu screen from 2 to 10 cycles mm^?1 frequency range while the modulation transfer function is lower from 0 to 5.5 cycles mm^?1 frequency range. The acquired data allow to predict that high-temperature sintering of our films under pressure may help to improve their imaging quality, since such a processing should increase the luminescence efficiency without significant growth of the grains and thus without sacrificing their translucent character.     

Wetting properties of aqueous solutions of hydrophobically modified inulin polymeric surfactant

The contact angles of aqueous solutions of a polymeric surfactant namely hydrophobically modified inulin (INUTEC®SP1) were measured on hydrophilic and hydrophobised quartz glass surfaces using the sessile drop technique. These measurements showed a large difference (>10°) between the advancing contact angle θ ₁ (that is measured immediately after placing the drop on the surface) and the constant contact angle θ ₂ (that is measured 30 minutes after placing the drop). In all the results only the contact angle θ ₂ was subsequently measured. θ versus INUTEC®SP1 concentration C _s curves were obtained at various NaCl concentrations both on hydrophilic and hydrophobic glass surfaces. On hydrophilic glass surface the θ versus C _s curves showed a maximum at a concentration range of 10^–6 to 2?×?10^–5 mol dm^-3 INUTEC®SP1. These curves were shifted to lower values as the NaCl concentration was increased. On such hydrophilic surface the INUTEC®SP1 molecule adsorbs with the polyfructose loops and tails oriented towards the surface leaving the alkyl chains in solution. Saturation adsorption with this orientation occurs at 2?×?10^–5 mol dm^-3 INUTEC®SP1. However, the contact angles remain quite small (<18°) indicating the presence of several hydrophilic glass patches uncovered by surfactant molecules. At C _s?>?2?×?10^–5 mol dm^-3 θ decreases with further increase of the INUTEC®SP1 concentration reaching 5° at the Critical Association Concentration (CAC) of the polymer. This indicates the formation of a bilayer of INUTEC®SP1 molecules with the alkyl chains hydrophobically attached to those of the first layer. On a hydrophobic glass surface, adsorption of INUTEC®SP1 occurs by multi-point attachment with the alkyl chains on the surface leaving the hydrophilic polyfructose loops and tails dangling in solution. This results in a gradual decrease of the contact angle with increase in INUTEC®SP1 concentration, reaching a plateau value (>85°) between 2?×?10^–5 and 2?×?10^–4 mol dm^-3. The large contact angles obtained on adsorption of the polymeric surfactant on a hydrophobic surface indicate the presence of several uncovered hydrophobic patches. These results give a reasonable picture of the adsorption and orientation of the INUTEC®SP1 molecules on both hydrophilic and hydrophobic solid surfaces.     

General non-catalytic approach to spiroacenaphthylene heterocycles: multicomponent assembling of acenaphthenequinone,cyclic CH-acids and malononitrile

The new type of non-catalytic cascade reaction was found: the direct multicomponent reaction of acenaphthenequinone, cyclic CH-acids, and malononitrile to form spiroacenaphthylene heterocycles. The direct heating in water acenaphthenequinone, cyclic CH-acids, and malononitrile at 80 °C results in the formation of spiroacenaphthylene heterocycles in 90–95% yields. Thus, a new simple and efficient green ‘one-pot’ method to synthesize substituted spiroacenaphthylene frameworks was found directly from simple starting compounds. The application of this convenient green multicomponent method is also beneficial from the viewpoint of diversity-oriented large-scale processes.     

Cascade assembly of N,N′-dialkylbarbituric acids and aldehydes: a simple and efficient one-pot approach to the substituted 1,5-dihydro-2H,2′H-spiro(furo[2,3-d]pyrimidine-6,5′-pyrimidine)-2,2′,4,4′,6′(1′H,3H,3′H)-pentone framework

Cascade assembly of N,N′-dialkylbarbituric acids and aldehydes in the presence of bromine leads to the selective and efficient formation of substituted 1,5-dihydro-2H,2′H-spiro(furo[2,3-d]pyrimidine-6,5′-pyrimidine)-2,2′,4,4′,6′-(1′H,3H,3′H)-pentones in 70-88% yields via a complex cascade process. Spirobarbiturates containing the furo[2,3-d]pyrimidine framework are a class of compounds with interesting pharmacological and physiological activity.     

Quantum-inspired resonance for associative memory

A new kind of dynamics for simulations based upon quantum-classical hybrid is discussed. The model is represented by a modified Madelung equation in which the quantum potential is replaced by different, specially chosen potentials. As a result, the dynamics attains both quantum and classical properties: it preserves superposition and entanglement of random solutions, while allowing one to measure its state variables using classical methods. Such an optimal combination of characteristics is a perfect match for quantum-inspired information processing. In this paper, the retrieval of stored items from an exponentially large unsorted database is performed by quantum-inspired resonance using polynomial resources due to quantum-like superposition effect.     

Heterogenization of metalorganic catalysts of olefin polymerization and evaluation of active site non-uniformity

Heterogenized activators - “support-H₂O/AlR₃” (where R=Me, iBu, support=montmorillonite, zeolite), synthesized directly on the support, form with metallocenes metal alkyl complexes highly active in olefin polymerization without the use of commercial methylaluminoxane (MAO). It was shown by the method of temperature programmed desorption with the application of mass-spectrometry (TPD-MS) that the aluminumorganic compound in support-H₂O/AlR₃ is in general similar to the structure of commercial MAO. The heterogenization of Zr-cenes on support-H₂O/AlR₃ is accompanied by the appearance of the energy non-uniformity of active sites. The activation energy of thermal destruction of active Zr-C bonds in the active sites of prepared catalysts changes in the range from 25 to 32 kcal/mol.     

Electrocatalytic Fast and Efficient Multicomponent Approach to Medicinally Relevant (2‐Amino‐4H‐chromen‐4‐yl) phosphonate Scaffold

‘One‐pot’ electrocatalytic transformation of salicylaldehydes, malononitrile, and triethyl phosphite in an undivided cell results in the formation of diethyl (2‐amino‐3‐cyano‐4H‐chromen‐4‐yl)phosphonates in 88–93% substance yields and 880–930% current efficiency via complex multicomponent process. This novel electrocatalytic chain process opens an effective, fast, and convenient way to cyano‐functionalized (2‐amino‐4H‐chromen‐4‐yl)phosphonate systems which are promising compounds for biomedical applications. This efficient electrocatalytic approach to the (2‐amino‐4H‐chromen‐4‐yl)phosphonate scaffold represents novel synthetic concept for multicomponent reactions (MCR) strategy and allows to combine the synthetic virtues of conventional MCR with ecological benefits and convenience of facile electrocatalytic procedure.