Synthesis and reduction of 5-halo-and 5-nitro-1-(benzofuran-3-yl)-2-phenylethanones

Novel 1-(2-alkylbenzofuran-3-yl)-2-(4-methoxyphenyl)ethanones having a halogen or nitro group in position 5 of the benzofuran ring were synthesized starting with the corresponding 2-(2-formylphenoxy)alkanoic acids. 1-(2-Alkylbenzofuran-3-yl)-2-phenylethanols containing bromine or chlorine atom were prepared in high yields by reduction of the corresponding ethanones with lithium aluminum hydride. Selective catalytic reduction of nitro 1-(2-alkylbenzofuran-3-yl)-2-(4-methoxyphenyl)ethanones to the corresponding amino compounds under Pd/C in room temperature was achieved. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1158–1166, August, 2006.     

Spin-crossover behavior in a new series of iron (II) compounds based on the ligand 5-(2-pyridyl)-1,2,4-triazole

The title ligand (hereafter LL), is found to form an exciting new series of pseudo-octahedral Fe(II) compounds with formula Fe(LL)₃X₂. N Solvent, which exhibit conveniently studied spin-crossover transformations between nominal⁵T and¹A states of Fe(II). Mössbauer spectra indicate that the spin-crossover transformations for these new systems are probably of the continuous type. There is considerable variation in the degree of conversion to low spin with decreasing temperature depending on gegen ion, solvation and/or location of methyl substituent on the triazole - ligand. The Mössbauer spectra for particular complexes in this group show an absence of both noticeable hysteresis and mechanical grinding effects.     

Determination of esters in glycerol phase after transesterification of vegetable oil

In biodiesel production, glycerol is formed as a side product and it is contained in the glycerol phase. This phase contains (besides glycerol): water, soaps, alcohol, traces of catalyst and glycerides and the remaining esters. In this paper, a new method for the determination of esters in the glycerol phase is introduced. The determination enables the minimization of the losses of biodiesel within the production process. It is based on the gradient RP-LC method (water and acetonitrile) with refractometric detection. The analysis is easy and the samples do not need any treatment (only dilution by water) and has a low detection limit. The results of this method were compared with the results of two other published methods: isocratic HPLC and GC. The disadvantage of these two methods is that they need extensive treatment of the sample, which takes many hours, and they are able to determine only the sum of esters. The new method is reliable, much faster and able to differentiate esters of almost each higher fatty acid (e.g. linoleic, linolenic, strearic alkyl ester) in the glycerol phase.     

Gender Diversity in a STEM Subfield – Analysis of a Large Scientific Society and Its Annual Conferences

Speaking engagements, serving as session chairs, and receiving awards at national meetings are essential stepping stones towards professional success for scientific researchers. Studies of gender parity in meetings of national scientific societies repeatedly uncover bias in speaker selection, engendering underrepresentation of women among featured presenters. To continue this dialogue, we analyzed membership data and annual conference programs of a large scientific society (>7000 members annually) in a male-rich (~70% males), technology-oriented STEM subfield. We detected a pronounced skew towards males among invited keynote lecturers, plenary speakers, and recipients of the society’s Senior Investigator award (15%, 13%, and 8% females, respectively). However, the proportion of females among Mid-Career and Young Investigator award recipients and oral session chairs resembled the current gender distribution of the general membership. Female members were more likely to present at the conferences and equally likely to apply and be accepted for oral presentations as their male counterparts. The gender of a session chair had no effect on the gender distribution of selected applicants. Interestingly, we identified several research subareas that were naturally enriched (i.e., not influenced by unequal selection of presenters) for either female or male participants, illustrating within a single subfield the gender divide along biology-technology line typical of all STEM disciplines. Two female-enriched topics experienced a rapid growth in popularity within the examined period, more than doubling the number of associated researchers. Collectively, these findings contribute to the contemporary discourse on gender in science and hopefully will propel positive changes within this and other societies.

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Critical behaviour in the shear elasticity of adamantane in the plastic phase

The elastic constants of the molecular crystal adamantane (C₁₀H₁₆) have been measured at 10 MHz as a function of temperature in the cubic plastic phase, with special attention given to the region just above the order-disorder transition into the tetragonal rigid phase. Both the velocity and attenuation of the C′ shear wave exhibit incipient critical behavior near this transition. The C′ stiffness also shows a pretransitional softening when this transition is approached by increasing the pressure along several isotherms.     

Electrical Conductivity and Percolation Aspects of Statistically Homogeneous Porous Media

A method of 3-D stochastic reconstruction of porous media based on statistical information extracted from 2-D sections is evaluated with reference to the steady transport of electric current. Model microstructures conforming to measured and simulated pore space autocorrelation functions are generated and the formation factor is systematically determined by random walk simulation as a function of porosity and correlation length. Computed formation factors are found to depend on correlation length only for small values of this parameter. This finding is explained by considering the general percolation behavior of a statistically homogeneous system. For porosities lower than about 0.2, the dependence of formation factor on porosity shows marked deviations from Archie's law. This behavior results from the relatively high pore space percolation threshold (0.09) of the simulated media and suggests a limitation to the applicability of the method to low porosity media. It is additionally demonstrated that the distribution of secondary porosity at a larger scale can be simulated using stochastic methods. Computations of the formation factor are performed for model media with a matrix-vuggy structure as a function of the amount and spatial distribution of vuggy porosity and matrix conductivity. These results are shown to be consistent with limited available experimental data for carbonate rocks.     

Computational insights into the mechanism of radical generation in B12-dependent methylmalonyl-CoA mutase

ONIOM calculations have provided novel insights into the mechanism of homolytic Co-C5' bond cleavage in the 5'-deoxyadenosylcobalamin cofactor catalyzed by methylmalonyl-CoA mutase. We have shown that it is a stepwise process in which conformational changes in the 5'-deoxyadenosine moiety precede the actual homolysis step. In the transition state structure for homolysis, the Co-C5' bond elongates by approximately 0.5 Angstroms from the value found in the substrate-bound reactant complex. The overall barrier to homolysis is approximately 10 kcal/mol, and the radical products are approximately 2.5 kcal/mol less stable than the initial ternary complex of enzyme, substrate, and cofactor. The movement of the deoxyadenosine moiety during the homolysis step positions the resulting 5'-deoxyadenosyl radical for the subsequent hydrogen atom transfer from the substrate, methylmalonyl-CoA.