Photoinduced hydrogen atom abstraction in N-(adamantyl)phthalimides: structure-reactivity study in the solid state

Adamantyl-functionalized phthalimides were synthesized and the probability of intramolecular photochemical hydrogen atom abstraction in the solid state analyzed by X-ray crystallographic analyses. These analyses and solid-state photolyses showed that the parameters determining photochemical reactivity for typical carbonyl compounds in the solid state can also be extended to phthalimides. Only N-(2-adamantyl)phthalimide underwent a solid-state photochemical reaction, which is the first example in the phthalimide series. This reaction is regio- and stereoselective, resulting in an endo-alcohol. On the other hand, the photoreaction of N-(2-adamantyl)phthalimide in solution gives an exo-alcohol as the main product together with an endo-alcohol and a benzazepindione.     

Tension spline collocation methods for singularly perturbed Volterra integro-differential and Volterra integral equations

We consider the numerical discretization of singularly perturbed Volterra integro-differential equations (VIDE)

(*)

and Volterra integral equations (VIE)

(**)

by tension spline collocation methods in certain tension spline spaces, where is a small parameter satisfying 0<1, and q₁, q₂, g and K are functions sufficiently smooth on their domains to ensure that Eqs. (*) and (**) posses a unique solution.We give an analysis of the global convergence properties of a new tension spline collocation solution for 0<1 for singularly perturbed VIDE and VIE; thus, extending the existing theory for =1 to the singularly perturbed case.     

Methyl radical also reacts by the frontside mechanism: an ab initio study of some homolytic substitution reactions of methyl radical at silicon,germanium and tin

Ab initio calculations using 6-311G**, cc-pVDZ, aug-cc-pVDZ, and a (valence) double-zeta pseudopotential (DZP) basis sets, with (MP2, QCISD, CCSD(T)) and without (UHF) the inclusion of electron correlation, and density functional (B3LYO) calculations predict that homolytic substitution reactions of the methyl radical at the silicon atom in disilane can proceed via both backside and frontside attack mechanisms. At the highest level of theory (CCSD(T)/aug-cc-pVDZ//MP2/aug-cc-pVDZ), energy barriers (delta E) of 47.4 and 48.6 kJ mol-1 are calculated for the backside and frontside reactions respectively. Similar results are obtained for reactions involving germanium and tin with energy barriers (delta E) of between 46.5 and 67.3, and 41.0 and 73.3 kJ mol-1 for the backside and frontside mechanisms, respectively. These data suggest that homolytic substitution reactions of methyl radical at silicon, germanium, and tin can proceed via either homolytic substitution mechanism.     

Working Methods Paper: Certification of methylmercury compounds concentration in marine sediment reference material,IAEA-356

An intercomparison exercise was organized between seven laboratories using various isolation procedures (extraction, distillation, ion-exchange and alkaline digestion) and detection systems (CV AAS, cold vapour atomic absorption spectroscopy; CV AFS, cold vapour atomic fluorescence spectroscopy; GC, ECD, gas chromatography electron capture detector and HPLC with CV AFS detection) for determination of methylmercury compounds in sediment sample. All certification criteria were fulfilled and therefore the value for total concentration of methylmercury compounds was certified to be 5.46 ng g^?1, with a 95% confidence interval from 4.07–5.84 ng g^?1. The acceptable range, calculated as two times the confidence interval of the mean is therefore from 4.68–6.23 ng g^?1. This is the first sediment reference material ever to be certified for concentration of methylmercury compounds. Comparison of the data obtained by various methodologies has shown that the most critical step is the isolation of methylmercury compounds from binding sites. Acid leaching only cannot release methylmercury compounds quantitatively. Total release of methylmercury compounds could only be achieved by alkaline digestion or distillation. This simple intercomparison exercise has shown that since large numbers of laboratories world-wide are performing methylmercury compound analyses using various improved and specific separation methods and sensitive detection systems, certification of methylmercury compounds in different biological and environmental samples should not be a problem in the future.     

K^0 - \bar K^0 mixing and the chiral-bag model

TheB-parameter is determined by the chiralbag model calculation of the amplitude. This is correlated with theK⁺⁰ decay amplitude. The theoretical magnitude ofB-parameter depends on the final state interaction effects inK2 decays. Without the final state interaction correction one findsB(µ _B ² )0.37, with the correction includedB(µ _B ² )0.9. Similar connection between theoretical prediction of theK⁺⁰ decay amplitude and calculated value ofB parameter seems to exist in other approaches too.     

Qualitative Identification of Metal Ions in Honey by Two-Dimensional Thin-Layer Chromatography

JPC – Journal of Planar Chromatography – Modern TLC - Two-dimensional thin-layer chromatography (2D TLC) has been used as a screening method for detection of the metal ions Al3+, Cr3+,...