Multi-functional architectures supported on organostannoxane scaffolds

Organostannoxane cages and aggregates of well-defined composition and structure can be prepared by the reactions of organotin oxides or organotin oxide-hydroxides with protic acids. The utility of this strategy for the preparation of dendrimer-like molecules containing a stannoxane core and a functional periphery is described.     

Synthesis of N-protected indolaldehydes using modified Hass procedure

A detailed study on oxidation of N-protected bromomethylindoles into the respective aldehydes was carried out. Using a modified Hass procedure, synthesis of aryl-/hetero-aryl aldehydes in particular indolaldehydes is achieved in reasonable yields.     

Insights into the oxidation of propylene oxide through the analysis of experiments and kinetic modeling

Cyclic ethers are important intermediates in the oxidation of hydrocarbons and biofuels. Studying the oxidation and pyrolysis of cyclic ethers will help in improving our understanding of this functional group and provide consistency to the base mechanism where they play an important role. In this aspect, propylene oxide has been investigated in this study by obtaining ignition delay time measurements in the rapid compression machine and shock tube. The experiments were performed in a range of pressures varying from 10 to 40 bar at different equivalence ratios (0.5–2.0) and dilution percentages. Additionally, speciation measurements in the shock tube at pyrolysis conditions have been performed at a pressure of 40 bar to explore the isomerization pathways. A detailed kinetic mechanism was developed to describe both the oxidation and pyrolysis chemistry of propylene oxide. The mechanism is not only able to predict the data obtained from this study but also reproduces the data from the literature in a consistent trend. For a better understanding of the oxidation and pyrolysis chemistry of propylene oxide, the kinetic analyses were performed using the developed mechanism to comprehend the important reaction pathways and sensitive reactions. At the investigated regime, the consumption of propylene oxide through its isomerization channels is the critical pathway that controls the reactivity of the fuel.     

Synthesis of oxacalothrixin B and its analogues involving iodine/TBHP-mediated electrocyclization

The total synthesis of oxacalothrixins, an isostere of biologically important carbazoloquinone alkaloid, calothrixin B was achieved from 2-acetyl-3-methylbenzofuran. An iodine/TBHP-mediated oxidative cyclization of benzofuranyl-enamine has been employed as a key step to synthesize, the crucial intermediate 1-hydroxy dibenzofurancarbaldehyde. The latter upon reductive cyclization followed by PIDA-mediated oxidation furnished oxacalothrixin B and its analogues.     

Sonoassisted Microbial Reduction of Chromium

This study presents sonoassisted microbial reduction of hexavalent chromium (Cr(VI)) using Bacillus sp. isolated from tannery effluent contaminated site. The experiments were carried out with free cells in the presence and absence of ultrasound. The optimum pH and temperature for the reduction of Cr(VI) by Bacillus sp. were found to be 7.0 and 37 °C, respectively. The Cr(VI) reduction was significantly influenced by the electron donors and among the various electron donors studied, glucose offered maximum reduction. The ultrasound-irradiated reduction of Cr(VI) with Bacillus sp. showed efficient Cr(VI) reduction. The percent reduction was found to increase with an increase in biomass concentration and decrease with an increase in initial concentration. The changes in the functional groups of Bacillus sp., before and after chromium reduction were observed with FTIR spectra. Microbial growth was described with Monod and Andrews model and best fit was observed with Andrews model.     

Molecular structure and vibrational spectra of indole and 5-aminoindole by density functional theory and ab initio Hartree–Fock calculations

The molecular geometry and vibrational frequencies of indole and 5-aminoindole in the ground state have been calculated by using the Hartree–Fock and density functional method with 6-311++G(d,p) basis set. The optimized geometrical parameters obtained by DFT calculations are in good agreement with the experimental values. Comparison of the observed fundamental vibrational frequencies of indole and 5-aminoindole with the calculated results by density functional and Hartree–Fock methods indicates that B3LYP is superior to the scaled Hartree–Fock approach for molecular vibrational problems. The theoretical spectrograms for FT-IR spectrum of 5-aminoindole have been constructed.     

Vibrational investigation on FT-IR and FT-Raman spectra, IR intensity, Raman activity, peak resemblance, ideal estimation, standard deviation of computed frequencies analyses and electronic structure on 3-methyl-1,2-butadiene using HF and DFT (LSDA/B3LYP/B3PW91) calculations

FT-IR and FT-Raman (4000–100 cm⁻¹) spectral measurements of 3-methyl-1,2-butadiene (3M12B) have been attempted in the present work. Ab-initio HF and DFT (LSDA/B3LYP/B3PW91) calculations have been performed giving energies, optimized structures, harmonic vibrational frequencies, IR intensities and Raman activities. Complete vibrational assignments on the observed spectra are made with vibrational frequencies obtained by HF and DFT (LSDA/B3LYP/B3PW91) at 6-31G(d,p) and 6-311G(d,p) basis sets. The results of the calculations have been used to simulate IR and Raman spectra for the molecule that showed good agreement with the observed spectra. The potential energy distribution (PED) corresponding to each of the observed frequencies are calculated which confirms the reliability and precision of the assignment and analysis of the vibrational fundamentals modes. The oscillation of vibrational frequencies of butadiene due to the couple of methyl group is also discussed. A study on the electronic properties such as HOMO and LUMO energies, were performed by time-dependent DFT (TD-DFT) approach. The calculated HOMO and LUMO energies show that charge transfer occurs within the molecule. The thermodynamic properties of the title compound at different temperatures reveal the correlations between standard heat capacities (C) standard entropies (S), and standard enthalpy changes (H).