Catalyzing Bond-Dissociation in Graphene via Alkali-Iodide Molecules.

Atomic design of a 2D-material such as graphene can be substantially influenced by etching, deliberately induced in a transmission electron microscope. It is achieved primarily by overcoming the threshold energy for defect formation by controlling the kinetic energy and current density of the fast electrons. Recent studies have demonstrated that the presence of certain species of atoms can catalyze atomic bond dissociation processes under the electron beam by reducing their threshold energy. Most of the reported catalytic atom species are single atoms, which have strong interaction with single-layer graphene (SLG). Yet, no such behavior has been reported for molecular species. This work shows by experimentally comparing the interaction of alkali and halide species separately and conjointly with SLG, that in the presence of electron irradiation, etching of SLG is drastically enhanced by the simultaneous presence of alkali and iodine atoms. Density functional theory and first principles molecular dynamics calculations reveal that due to charge-transfer phenomena the CC bonds weaken close to the alkali-iodide species, which increases the carbon displacement cross-section. This study ascribes pronounced etching activity observed in SLG to the catalytic behavior of the alkali-iodide species in the presence of electron irradiation.

Characterization of an insecticidal coumarin from Boenninghausenia albiflora.

The leaves of Boenninghausenia albiflora afforded an insecticidal coumarin which was identified as murraxocin (7-methoxy-8-[1'-ethoxy-2'-hydroxy-3'-methyl-but-3'enyl]-coumarin) (1), on the basis of extensive 1- and 2-dimensional NMR experiments. This compound has previously been isolated from Murraya exotica but this is the first report of the full (1)H and (13)C data for this compound. This natural product was evaluated against important forest insect pests and was active against Plecoptera reflexa, Clostera cupreata and Crypsiptya coclesalis at different concentrations varying from 1.0% to 5% w/v. In the crude extract 70% mortality was observed, and for compound 1 80% mortality was observed at a concentration of 1.0% w/v. The percentage of insect mortality increased in a dose-dependent manner. Coumarins are poorly studied insecticides and there is potential to exploit this chemically simple group of natural products.

Direct one-pot conversion of acylated carbohydrates into their alkylated derivatives under heterogeneous reaction conditions using solid NaOH and a phase transfer catalyst.

A convenient one-pot protocol for the direct conversion of acyl-protected carbohydrates into their alkylated counterparts has been developed by using alkyl halides in the presence of solid sodium hydroxide and a phase transfer catalyst. These economically convenient, mild, two-phase reaction conditions allow the preparation of a variety of monosaccharide intermediates for use in the synthesis of complex oligosaccharides.