Non-Born-Oppenheimer treatment of the H2 Hookean molecule

We show that the exact non-Born-Oppenheimer Schrodinger equation for the Hookean diatomic molecule H2 (a two-proton, two-electron system where the electron-proton interaction is harmonic while the proton-proton and electron-electron interactions are Coulombic) can be decoupled into equations describing the relative motion of the electrons, the relative motion of nuclei, the motion of a collective mode representing a three-dimensional harmonic oscillator, and the motion of a free particle expressed as a linear combination of the individual center-of-mass coordinates of the nuclei and electrons. Analytic solutions to the relative motion of electrons can be readily obtained for the given values of the harmonic coupling constant. However, exact analytic solutions to the equation for the relative motion of the nuclei cannot be obtained simultaneously due to the fact that the harmonic constants in these two equations are coupled. For this reason, we present for the relative nuclear motion approximate analytic wave functions, one of them obtained variationally and the other by a series solution where the coefficients are determined recursively. We also explore a variational solution to the Taylor-series expansion of the nuclear interaction potential. Properties of the electronic and nuclear intracule densities are examined at different values of the coupling constant. An interesting result of the present non-Born-Oppenheimer treatment of this harmonic model is the fact that the relative nuclear motion occurs in a highly correlated regime. This leads in a natural way to a spatial localization of the nuclei akin to Wigner electronic crystallization.     

Equilibrium interaction of solid surfaces across a polymer melt

Forces across polymer melts are poorly understood despite their importance for adhesion and fabricating composite materials. Using an atomic force microscope (AFM), this interaction was measured for poly(dimethyl siloxane) (PDMS). The structure of the polymer at the surface changed during the first approximately 10 h. Afterward, short-range attractive forces were observed with short-chain PDMS (M(w) = 4200 g/mol). Using PDMS with a molecular weight (M(w) = 18 000 g/mol) above the entanglement limit, we measured a monotonically decaying repulsive force, which indicates that a quasi-immobilized layer had formed at the solid surface. Due to the small radius of curvature of the tip, forces could be measured in equilibrium.     

Ester synthesis catalyzed by Mucor miehei lipase immobilized on magnetic polysiloxane-polyvinyl alcohol particles

Mucor miehei lipase was immobilized on magnetic polysiloxane-polyvinyl alcohol particles by covalent binding with high activity recovered. The performance of the resulting immobilized biocatalyst was evaluated in the synthesis of flavor esters using heptane as solvent. The impact on reaction rate was determined for enzyme concentration, molar ratio of the reactants, carbon chain length of the reactants, and alcohol structure. Ester synthesis was maximized for substrates containing excess acyl donor and lipase loading of 25 mg/mL. The biocatalyst selectivity for the carbon chain length was found to be different concerning the organic acids and alcohols. High reaction rates were achieved for organic acids with 8 or 10 carbons, whereas increasing the alcohol carbon chain length from 4 to 8 carbons gave much lower esterification yields. Optimal reaction rate was determined for the synthesis of butyl caprylate (12 carbons). Esterification performance was also dependent on the alcohol structure, with maximum activity occurring for primary alcohol. Secondary and tertiary alcohols decreased the reaction rates by more than 40%.     

Synthesis and spectral properties of 2,3-dihydro-4-(para-substituted-phenyl)-7-[(o-, m-, and p-substituted)phenoxy]-1H-1,5-benzodi-azepine-2-thiones

A series of twelve new 2,3-dihydro-4-(para-substituted-phenyl)-7-[(o-, m-, and p-substituted)phenoxy]-1H-1,5-benzodiazepine-2-thiones, which have potentially useful pharmacological properties, has been synthesized by condensing the 3,3-dimercapto-1-(para-substituted phenyl)-2-propen-1-one with 3,4-diaminophenyl-R-phenyl ethers. The structure of all products was corroborated by ir, ¹H-nmr, ¹³C-nmr and ms.     

A flow-through cell for differential pulse anodic stripping voltammetry

A flow-through voltammetric cell with a hanging mercury drop electrode has been developed to fit the static mercury drop electrode (PAR 303). The design has resulted in a linear increase of sensitivity with flow rate and an enhancement of sensitivity by the wall-jet effect. The cell is used in a flow injection system in which samples are introduced with a R??i?ka—Hansen injector. The mercury drop is held at plating potentials while the sample peak passes through the cell. Stripping is done under stopped flow conditions, to reduce noise, after the sample has been washed completely from the cell. The stripping thus takes place into the carrier electrolyte which always has a constant composition independent of sample constituents. Film-forming interfering species will, however, remain on the surface of the mercury drop. The effect of medium exchange on films produced by l-cysteine is reported. The flow-through medium exchange simplifies deaeration, speeds up analysis and reduces contamination.     

Synthesis and spectral properties of 6H-2,7,7-trimethyl-4-(o,p-R-phenylamino)-7,8-dihydrofuro[3,2-c]azepines

The preparation of nine novel 6H-2,7,7-trimethyl-4(o-,p-R-phenylamino)-7,8-dihydrofuro[3,2-c]-azepines with possible pharmacological activity is described. The structure of all products was corroborated by ir, ¹H-nmr and ms.     

Mitsunobu reactions of nucleoside analogs using triisopropyl phosphite-DIAD

Herein, we report the use of triisopropyl phosphite (TIP) as an effective substitute for triphenylphosphine in the Mitsunobu reaction of nucleoside analogs. In addition, the use of triphenyl phosphite as an alternative reagent for the expensive hexamethylphosphorous triamide (HMPT) in the Véliz-Beal bromination protocol is reported.     

Unexpected formation of 1-diethylaminobutadiene in photosensitized oxidation of triethylamine induced by 2,3-dihydro-oxoisoaporphine dyes. A 1H NMR and isotopic exchange study

[reaction: see text] Photoreduction of oxoisoaporphine dyes occurs via a stepwise mechanism of electron-proton-electron transfer that leads to the N-hydrogen oxoisoaporphine anion. When triethylamine, TEA, was used as the electron donor in anaerobic conditions, 1-diethylaminobutadiene, DEAB, was one of the oxidation products of TEA, among diethylamine and acetaldehyde. DEAB was identified by (1)H NMR and GC-MS experiments by comparison with the authentic 1-diethylaminobutadiene. This is the first report of a butadienyl derivative formed in the dye-sensitized photooxidation of TEA. In addition, isotopic exchange experiments with TEA-d(15) and D(2)O show that the hydrogens at carbon-2 and carbon-4 of the butadienyl moiety are exchangeable. The observed isotopic exchange pattern could be explained by the head-to-tail coupling of an N,N-diethylvinylamine intermediate that exchanges hydrogens at the C-beta via the enammonium ion.     

Unsupported gold(I)-copper(I) interactions through eta1 Au-[Au(C6F5)2]- coordination to Cu+ Lewis acid sites

The reaction of the complex [Au2Ag2(C6F5)4)N[triple bond]CCH3)2]n (1) with 1 equiv of CuCl in the presence of 1 equiv of pyrimidine ligand leads to the formation of the heteronuclear Au(I)-Cu(I) organometallic polymer [Cu{Au(C6F5)2}(N[triple bond]CCH3)(mu2-C4H4N2)]n (2) through a transmetalation reaction. Complex 2 displays unprecedented unsupported Au(I)...Cu(I) interactions of [Au(C6F5)2]- units with the acid Cu(I) sites in a [Cu(N[triple bond]CCH3)(mu2-pyrimidine)]n+(n) polymeric chain. Complex 2 has a rich photophysics in solution and in the solid state.