Electron-impact-induced 3,3-sigmatropic rearrangement and cyclization in phenyl allenylmethyl ethers

A 3,3-sigmatropic rearrangement in the M^+· of phenyl allenylmethyl ether is proposed for the observed losses of CO, C₂H₄, and CH₃. Direct cyclization in the M^+· also leads to the [M?CH₃] ion. The presence of sulfur as the heteroatom in phenyl allenylmethyl sulfide does not significantly influence the occurrence of Claisen rearrangement. Ortho interaction of the nitro group with the allenyl double bond in the side chain leads to characteristic fragment ions in 2-nitrophenyl allenylmethyl ether. Linked scans, high-resolution mass spectrometry, collision-activated dissociation-B/E linked-scan spectra, and D-labeling have been employed to support the proposed mechanisms and ion structures.     

Oxidative amidation of benzyl alcohols with amino acid esters mediated by N-hydroxysuccinimide/phenyliodine diacetate

A simple protocol involving metal-free oxidative amidation of benzyl alcohols with amino acid esters has been presented. The amidation proceeds in a radical pathway unlike in conventional metal-mediated extrusion of dihydrogen. The method is advantageous in terms of metal-free conditions, nonexpensive commercial starting substrates. Also various substituents in the starting materials are tolerated and sterically hindered amino acid side chains could provide good yields of amide products.     

A short and concise route to total synthesis of Dendrodolide L

A short and efficient method for the stereoselective synthesis of Dendrodolide L has been developed from inexpensive and commercially available starting material. This convergent synthesis utilizes Jacobsen kinetic resolution, regioselective ring-opening of epoxide and Yamaguchi macrolactonization as key steps.     

Limitations in the use of horseradish peroxidase as an enyzme probe in the development of a homogeneous immunoassay for aflatoxin B1

Horseradish peroxidase (HRPO) was used as a probe to quantitate aflatoxin B₁ by a homogeneous immunoassay. The conjugation of AFB₁ to HRPO resulted in 54% loss of enyzme activity. In the presence of AFB₁ specific antibodies, the HRPO-AFB₁ conjugate showed reversal of its lost enzyme activity by 12%. This positive modulatory effect of antibody on the enzyme activity was used as an analytical tool to quantitate AFB₁. The homogeneous assay carried out with free AFB₁ and HRPO-AFB₁ conjugate in the presence of antibodies indicated poor linearity as compared to the heterogeneous assay. It was observed that the number of HRPO-lysine residues involved in AFB₁ conjugation were 6–8. The low level of modulation of enzyme activity by antibody with respect to HRPO-AFB₁ conjugate, could possibly be attributed to the limited number of lysine residues in the HRPO molecule and its proximity to the active site of the enzyme. Thus, HRPO was found to be limiting as an enzyme with respect to the homogeneous enzyme immunoassay for AFB₁ analysis. The antibodies raised were specific for AFB₁, and showed excellent linearity even at high dilution for the detection of AFB₁ by ELISA indicating that antibodies per se were not the limiting factor.     

Growth and surface characterization of sputter-deposited molybdenum oxide thin films

Molybdenum oxide thin films were produced by magnetron sputtering using a molybdenum (Mo) target. The sputtering was performed in a reactive atmosphere of an argon-oxygen gas mixture under varying conditions of substrate temperature (T_s) and oxygen partial pressure (pO₂). The effect of T_s and pO₂ on the growth and microstructure of molybdenum oxide films was examined in detail using reflection high-energy electron diffraction (RHEED), Rutherford backscattering spectrometry (RBS), energy-dispersive X-ray spectrometry (EDS), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) measurements. The analyses indicate that the effect of T_s and pO₂ on the microstructure and phase of the grown molybdenum oxide thin films is remarkable. RHEED and RBS results indicate that the films grown at 445 °C under 62.3% O₂ pressure were stoichiometric and polycrystalline MoO₃. Films grown at lower pO₂ were non-stoichiometric MoO_x films with the presence of secondary phase. The microstructure of the grown Mo oxide films is discussed and conditions were optimized to produce phase pure, stoichiometric, and highly textured polycrystalline MoO₃ films.     

Synthesis, characterization and photocatalytic properties of novel zinc germanate nano-materials

We report the first instance of a hydrothermal synthesis of zinc germanate (Zn₂GeO₄) nano-materials having a variety of morphologies and photochemical properties in surfactant, template and catalyst-free conditions. A systematic variation of synthesis conditions and detailed characterization using X-ray diffraction, ultraviolet-visible diffuse reflectance spectroscopy, Raman spectroscopy, electron microscopy, X-ray photoelectron spectroscopy and small angle X-ray scattering led to a better understanding of the growth of these particles from solution. At 140 °C, the zinc germanate particle morphology changes with pH from flower-shaped at pH 6.0, to poly-disperse nano-rods at pH 10 when the Zn to Ge ratio in the synthesis solution is 2. When the Zn to Ge ratio is reduced to 1.25, mono-disperse nano-rods could be prepared at pH 7.5. Nanorod formation is also independent of the addition of cetyltrimethylammonium bromide (CTAB), in contrast to previous reports. Photocatalytic tests show that Zn₂GeO₄ nano-rods (by weight) and flower shaped (by surface area) are the most active for methylene blue dye degradation among the synthesized zinc germanate materials.     

Magnesium ion conducting, room temperature molten electrolytes

Room temperature, magnesium ion conducting binary molten electrolyte consisting of acetamide and magnesium perchlorate has been prepared and characterized. The molten liquid is very stable and shows high ionic conductivity, of the order of several mS cm⁻¹ at 25 °C with other favourable physicochemical properties. Vibrational spectroscopic studies reveal that the free ion concentration is higher than that of ion pairs and aggregates in the melt. The electrochemical reversibility of magnesium deposition and dissolution is demonstrated using voltammetry and impedance studies. Preliminary studies on rechargeable batteries assembled using γ-MnO₂ and Mg metal as the electrodes together with the molten electrolyte show high discharge capacity.