Potential volatile markers of brown rice infested by the rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae).

The rice weevil, Sitophilus oryzae (L.) (Coleoptera: Curculionidae) could cause significant grain loss by feeding internally on seeds. In this study, we tried to analyze the volatile compounds in non-infested and S. oryzae-infested brown rice during different storage periods to identify potential markers in S. oryzae-infested brown rice and facilitate pest monitoring during brown rice storage. Headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) and headspace-gas chromatography-ion mobility spectrometry (HS-GC-IMS) were used to identify the volatile compounds. On the basis of GC-MS and GC-IMS data, a reliable method to distinguish between non-infested and S. oryzae-infested brown rice was discovered using partial least squares-discriminant analysis (PLS-DA). 1-Octen-3-ol, 1-hexanol and 3-octanone were co-selected as potential markers because their variable importance in projection (VIP) was greater than 1 in both models. The current study's findings lay a foundation for further research on the brown rice infestation mechanism and safe storage monitoring.

Triflamidation of Allyl-Containing Substances:Unusual Dehydrobromination vs. Intramolecular Heterocyclization.

Allyl halides with triflamide under oxidative conditions form halogen-substituted amidines. Allyl cyanide reacts with triflamide in acetonitrile or THF solutions in the presence of NBS to give the products of bromotriflamidation with a solvent interception, whereas in CH2Cl2 two regioisomers of the bromotriflamidation product without a solvent interception were obtained. The formed products undergo base-induced dehydrobromination to give linear isomers with the new C=C bond conjugated either with the nitrile group or the amidine moiety or alkoxy group. Under the same conditions, the reaction of allyl alcohol with triflamide gives rise to amidine, which was prepared earlier by the reaction of diallyl formal with triflamide. Unlike their iodo-substituted analogs, bromo-substituted amidines successfully transform into imidazolidines under the action of potassium carbonate.

Competing Reaction Pathways in Heterogeneously Catalyzed Hydrogenation of Allyl Cyanide: The Chemical Nature of Surface Species.

We present a mechanistic study on the formation of an active ligand layer over Pd(111), turning the catalytic surface highly active and selective in partial hydrogenation of an α,ß-unsaturated aldehyde acrolein. Specifically, we investigate the chemical composition of a ligand layer consisting of allyl cyanide deposited on Pd(111) and its dynamic changes under the hydrogenation conditions. On pristine surface, allyl cyanide largely retains its chemical structure and forms a layer of molecular species with the CN bond oriented nearly parallel to the underlying metal. In the presence of hydrogen, the chemical composition of allyl cyanide strongly changes. At 100 K, allyl cyanide transforms to unsaturated imine species, containing the C=C and C=N double bonds. At increasing temperatures, these species undergo two competing reaction pathways. First, the C=C bond become hydrogenated and the stable N-butylimine species are produced. In the competing pathway, the unsaturated imine reacts with hydrogen to fully hydrogenate the imine group and produce butylamine. The latter species are unstable under the hydrogenation reaction conditions and desorb from the surface, while the N-butylimine adsorbates formed in the first reaction pathway remain adsorbed and act as an active ligand layer in selective hydrogenation of acrolein.