Experimental and theoretical studies of small-angle electron scattering by the water molecule

The total (elastic plus inelastic) intensities of 51 keV electrons scattered by water molecules have been measured over a range of 1 ≦ K = (4π/λ) sin(θ/2) ≦ 12 Å^?1. A computer program, ELIC, has been written for calculating the total intensities of electrons scattered by free molecules. The intensities can be calculated with self-consistent field and configuration interaction wavefunctions. The theoretical intensities based on a CI wavefunction are in good agreement with the observed intensities.     

Adsorption of anti-human IgG to plasma-polymerized allylamine film formed on a silver plate

Increase in the sensitivity of an immunosensor or biosensor requires the immobilization of a large amount of proteins. Good materials must be developed for this protein adsorption. Allylamine thin film was formed on a flat silver plate by plasma polymerization; this plate is referred to as Ag(ALAM). Ag(ALAM) films were characterized by SEM, FT–IR and ESCA. Investigations on adsorption and desorption of F(ab')₂ anti-human IgG (hIgG) on to Ag and Ag(ALAM) revealed the following: (1) The adsorption isotherm of F(ab')₂ anti-hIgG on to AG(ALAM) or Ag was of a Langmuir type. The binding constant (K_b) and saturation binding (A_b) for this protein on to Ag(ALAM) were 8.93 l/mol and 181.8 nmol/m², respectively, and for Ag, were 7.71 l/mole and 87.9 nmol/m². (2) The extent of desorption of labeled F(ab')₂ anti-hIgG absorbed on the two plates was the same. (3) Ag(ALAM) and Ag were used as solid phases in a two-site immunoradiometric assay of human serum IgG. The dose-response on AG(ALAM) occurred at lower concentration, and was of greater magnitude than that on Ag.     

Intramolecular radical cyclization-ring-closing metathesis approach to fused polycyclic ethers. Convergent synthesis and conformational analysis of the (E)FGH ring system of ciguatoxin

A convergent synthetic route to the (E)FGH ring system 4 of ciguatoxins, the causative toxins for ciguatera fish poisoning, has been developed. The synthesis features convergent coupling to form dioxane acetal, regioselective acetal cleavage by diethylaluminum phenylthiolate or diisobutylaluminum phenylselenolate followed by intramolecular radical cyclization to construct the oxepane ring G, and a ring-closing metathesis reaction to form the hexahydrooxonine ring F. The hexahydrooxonine ring F of tetracyclic model system 4 existed as a 5:1 equilibrium mixture of two conformers (UP and DOWN conformers), with the UP one predominating. This is the first illustration that reproduces the preference for the UP conformer over the DOWN one, which preference was observed for natural ciguatoxins.     

Oxidation-alcoholysis of organosilyl- and organogermyl-substituted ferrocenes in the presence of ferric ions

Eleven ferrocene derivatives bearing the MM (M = Si and/or Ge) substituent bonded directly to the ring have been found to undergo alcoholysis at the MM linkage in the presence of either ferric chloride or ferricenium tetrachloroferrate. It is suggested that the oxidation-reduction process between the ferrocene derivatives and ferric ions gives rise to the corresponding substituted ferricenium ions, which, in turn may readily undergo a nucleophilic attack by alcohol at the adjacent highly polarized MM bond. The reaction is thus very similar to the acid-catalyzed alcoholysis of these ferrocene derivatives.     

Regioselective synthesis of 4-alkylquinolines from quinoline via 1-ethoxycarbonyl-1, 2-dihydroquinoline-2-phosphonates

1-Ehtoxycarbonyl-1, 2-dihydroquinoline-2-phosphonates ($\text{3}$) were treated with n-butyllithium followed by alkyl halides to afford the corresponding 4-alkylated phosphonates ($\text{7}$) with complete regioselectivity in 67–97% yields. The phosphonates ($\text{7}$) were converted to 4-alkylquinolines ($\text{8}$) in ca. 50% yields by treatment with sodium iodide in HMPA or by alkaline hydrolysis in aqueous ethanol.     

Structural analysis of models for AsxS1−x glasses

The structural models of chalcogenide glasses As_xS_1?x for x = 0.2 and 0.5 have been constructed by the three-step procedure and the characteristic dependence of atomic scale structure on the As content has been analysed. The AsS bonds are most favorable and the distributions of bond lengths and bond angles are very narrow around their minimum energy configurations. The glass of x = 0.2 consists of cross-linked linear chains and the number of molecular units increases drastically in the range of x = 0.4 ≈ 0.5. Furthermore, the two-dimensional network cannot be seen for x = 0.2 and 0.5, which is the essential difference from the glass with x = 0.4.     

Surface diffusion kinetics of GaAs and AlAs metalorganic vapor-phase epitaxy

We have investigated the surface kinetics during metalorganic vapor-phase epitaxy (MOVPE), using high-vacuum scanning tunneling microscopy (STM) observation of two-dimensional (2D) nuclei and denuded zones. Using Monte Carlo simulations based on the solid-on-solid model, from 2D nucleus densities we estimated the surface diffusion coefficients of GaAs and AlAs to be 2 × 10⁻⁶ and 1.5 × 10⁻⁷ cm²/s at 530°C, and the energy barriers for migration to be 0.62 and 0.8 eV, respectively. The 2D nucleus size in the [110] direction was about two times larger than that in the [ 10] direction. The size anisotropy is caused primarily by a difference in the lateral sticking probability (P_s) between steps along the [ 10] direction (A steps) and steps along the [110] direction (B steps). The P_s ratio was estimated to be more than 3:1. Denuded zone widths on upper terraces were 2 ± 0.5 times wider than those on lower terraces. This showed that P_s at descending steps was 10 to 3 × 10² times larger than P_s at ascending steps.     

Synthesis of regiocontrolled polymer having 2-naphthol unit by CuCl-amine catalyzed oxidative coupling polymerization

Regiocontrolled polymer (2) having 2-naphthol unit was prepared by oxidative coupling polymerization of bis(2-naphthol) (1). Polymerizations were conducted in dichloromethane in the presence of [di-μ-hydroxo-bis(N,N,N′,N′-tetramethylethylenediamine)copper(II)] chloride [CuCl(OH)TMEDA] under air at room temperature, producing polymers with number-average molecular weights up to 12,000. The structure of polymer 2 was characterized by 270 MHz ¹H–NMR and 68.5 MHz ¹³C–NMR spectroscopies and was estimated to consist almost completely of 1,1′-linkage. The polymer was readily soluble in polar aprotic solvents and tetrahydrofuran at room temperature. Thermogravimetric analysis of polymer 2 showed 10% weight loss at 450°C in nitrogen. The model reactions were studied to clarify the applicability of CuCl(OH)TMEDA for coupling of naphthol derivatives. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 3702–3709, 1999