Vessel effects in organic chemical reactions; a century-old,overlooked phenomenon

One of the most intriguing aspects of synthetic chemistry is the interplay of numerous dependent and independent variables en route to achieve a successful, high-yielding chemical transformation. The experienced synthetic chemist will probe many of these variables during reaction development and optimization, which will routinely involve investigation of reaction temperature, solvent, stoichiometry, concentration, time, choice of catalyst, addition sequence or quenching conditions just to name some commonly addressed variables. Remarkably, little attention is typically given to the choice of reaction vessel material as the surface of common laboratory borosilicate glassware is, incorrectly, assumed to be chemically inert. When reviewing the scientific literature, careful consideration of the vessel material is typically only given during the use of well-known glass-etching reagents such as HF, which is typically only handled in HF-resistant, polyfluorinated polymer vessels. However, there are examples of chemical transformations that do not involve such reagents but are still clearly influenced by the choice of reaction vessel material. In the following review, we wish to condense the most significant examples of vessel effects during chemical transformations as well as observations of container-dependent stability of certain molecules. While the primary focus is on synthetic organic chemistry, relevant examples from inorganic chemistry, polymerization reactions, atmospheric chemistry and prebiotic chemistry are also covered.

One of the most intriguing aspects of synthetic chemistry is the interplay of numerous dependent and independent variables en route to achieve a successful, high-yielding chemical transformation.     

Gaussian Amplitude Amplification for Quantum Pathfinding

We study an oracle operation, along with its circuit design, which combined with the Grover diffusion operator boosts the probability of finding the minimum or maximum solutions on a weighted directed graph. We focus on the geometry of sequentially connected bipartite graphs, which naturally gives rise to solution spaces describable by Gaussian distributions. We then demonstrate how an oracle that encodes these distributions can be used to solve for the optimal path via amplitude amplification. And finally, we explore the degree to which this algorithm is capable of solving cases that are generated using randomized weights, as well as a theoretical application for solving the Traveling Salesman problem.     

Diffusion changes precede size reduction in neoadjuvant treatment of breast cancer

Traditionally, tumor response has been assessed via tumor size measurements during the course of a treatment. However, changes in these morphologically based measures occur relatively late in the course of a treatment. Alternative biomarkers are currently being evaluated to enable an earlier assessment of treatment to facilitate early cessation and cost savings. Diffusion-weighted imaging (DWI) has been identified by preclinical studies to be a likely alternative to tumor size measurements. In this study, 10 patients were examined prior to and after the first and second chemotherapy cycle time points. Longest diameter tumor measurements and apparent diffusion coefficients (ADCs) were recorded at each exam. An increase in the mean (normalized) ADC was noted as early as the first cycle time point. However, a reduction in the mean (normalized) longest diameter was only noted at the second cycle time point. Significant alterations from the baseline value were noted for ADC at the first (P=.005) and second cycle time points (P=.004). Longest diameter measurements only achieved a borderline significance at the second time point (P=.057). These results indicate that DWI may provide a suitable biomarker capable of providing an indication of response to treatment prior to tumor size measurements.     

Wafer thickness optimization for silicon solar cells of heterogeneous material quality

In this Letter, we introduce a method of calculating the optimal wafer thickness for silicon solar cells with multicrystalline bulk material. The optimal thickness depends on the relation of bulk recombination to surface recombination and the light trapping. For multicrystalline silicon bulk recombination strongly varies laterally and with injection level, which complicates the calculations. A thickness optimization using the “Efficiency Limiting Bulk Recombination Analysis” (ELBA) takes all these effects correctly into account. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Variability of procedural blanks leads to greater uncertainty in assessing detection limits for the measurement of polonium-210

Low-level measurements of ²¹⁰Po using alpha spectrometry with a ²⁰⁹Po tracer have been conducted at the Environmental Research Institute of the Supervising Scientist (eriss) for many years, on samples with a range of activity concentrations spanning several orders of magnitude. These samples originated from a wide range of research and monitoring projects, and included a wide variety of traditional foods consumed by the indigenous population in Australia’s Northern Territory. Assessment of instrument blank and analyte blank data from these measurements collected over a period of 8 years was conducted. Instrumental blank data for ²¹⁰Po and ²⁰⁹Po generally followed a normal distribution, whereas analyte blank data for ²¹⁰Po followed a lognormal distribution. Instrumental blank data for ²⁰⁹Po indicated an increasing trend, indicative of a low level of polonium volatilisation from prepared sources. Lower limits of detection, including the critical limit, detection limit and quantification limit have been calculated. The critical limit ranges from 12 to 37 counts per day. Detection and quantification limits range from 0.18 to 0.33 mBq and 2.3 to 3.6 mBq for a 4-day count, with an assumed mean chemical recovery of 53 %. These limits are relatively high for alpha spectrometric techniques due to the high variability of the analyte blank signal and non-normal distribution for ²¹⁰Po. Native plant species have relatively low activity concentrations of ²¹⁰Po in their edible fruits and the amount of sample that should be used for analysis to ensure 90 % of fruit samples analysed reach the specified quantification limit was 11 g.     

The Conformation of Sterically Congested Seven-Membered Rings Containing Tetracoordinate Germanium(IV): A First X-Ray Crystallographic Structure Determination

The X-ray crystallographic analysis of 6,6-dimethyl-2,4,8,10-tetra-tert-octyl-dibenzo[d,f][1,3,2]dioxagermepin, 1 is reported. In the solid-state conformation of 1, the dihedral angle about the C─C sp²-sp ² σ bond connecting the two aryl rings is 50.1°. The observed C₂ symmetry in the solid-state conformation of 1 is consistent with the previously suggested solution conformation.     

A Sucrose-Based Approach to Enantiomerically Pure Glycerol Derivatives

Abstract

Taking advantage of the same configuration present at C-5 and C-5′ in sucrose, 6,6′-diprotected sucrose derivatives were transformed into enantiomerically pure glycerol derivatives. This was achieved by oxidative ring cleavage of both the glucopyranosyl ring as well as the fructofuranosyl moiety followed by reduction of the resulting tetraaldehyde and subsequent per-O-protection of the resulting pentahydroxy compound. The obtained intermediate was hydrolysed under acidic conditions to furnish two equivalents of partially protected chiral glycerol derivative per molecule of starting material. The efficiencies of sodium metaperiodate and lead tetraacetate as oxidizing agents were compared and the side reactions observed in these procedures were investigated.