Ion-neutral complex-mediated hydrogen exchange in ionized n-butanol: A mechanism for ‘non-specific’ hydrogen migrations

Water elimination from ionized n-butanol reflects near randomization of all hydrogens in ions decomposing after ～10^?5s. This probably takes place in ion-neutral complexes by formation of a cyclobutane ion–H₂O complex and/or rearrangement within [C₄H₈]⁺˙ in open-chain [C₄H₈⁺˙? H₂O] complexes, in either case accompanied by hydrogen exchange between water and open-chain hydrocarbon moieties. Extensive hydrogen rearrangements in which restraints on conventional transition-state ring size have little apparent influence may generally be ion–neutral complex-mediated processes.     

Operator — Stable distributions with independent marginals

Summary Let be a full operator-stable probability measure over a finite dimensional real inner product space V. Necessary and sufficient conditions are obtained for to have independent univariate marginals with respect to some basis of V. These essentially amount to the statement that the support of the Lévy spectral measure is a subset of the union of one-dimensional subspaces of V determined by the vectors in a basis of the subspace of V spanned by the support of the non-Gaussian component. A representation for an exponent of such a is also given.The research of Howard G. Tucker was supported in part by the National Science Foundation, Grant No. MCS 8001583     

Origin of the [C4H9O]+ ions in the mass spectrum of n-butyl ethyl ether

The mechanisms of formation of m/z 73 ions in the mass spectrum of the ionized title compound were investigated by deuterium substitution and by examining the decompositions of metastable ions. Two routes to the [C₄H₉O]⁺ ions were found in the normal spectrum. The ethyl lost by the major pathway contains the α- and β-hydrogens and a γ-hydrogen from the butyl group. The minor route involves the loss of ethylene from the [M? H]⁺ ion. There were metastable peaks for losses of ethyl, ethanol and methyl from the molecular ion. The ethyl contains the α- and β-methylenes and a γ-hydrogen, while the methyl is the δ-methyl of the butyl group. The labeling data rule out a previous mechanistic proposal for the loss of ethyl and support a mechanism involving stepwise isomerization to the sec-butyl ethyl ether molecular ion. However, the metastable ion chemistries of the molecular ions from the n- and sec-butyl ethyl ethers are highly dissimilar, perhaps due to decompositions from different electronic states. The n-pentyl methyl ether ions loses both ethyl and propyl, apparently following rearrangements to the 3-pentyl and 2-pentyl ether ions. Di n-butyl and n-butyl methyl ethers also give metastable peaks for loss of methyl, ethyl and the shorter chain alcohol.     

Microwave-assisted three component one-pot synthesis of pyrimido-oxazepines

A synthetic approach toward pyrimido-oxazepine analogs was developed through the use of microwave heating. Certain analogs can be made in one step, which make this a valuable tool in the investigation of this therapeutically relevant scaffold.     

Colloidal particles coated and stabilized by DNA-wrapped carbon nanotubes

Single-walled carbon nanotubes (SWNTs) are dispersed in water via wrapping with short segments of single-stranded DNA (ssDNA). Small angle neutron scattering suggests a power-law exponent that is consistent with clustered nanotubes and hence marginal stability. The SWNT-ssDNA complex is used to stabilize dispersions of hydrophilic colloidal particles with the nanotubes adhered to the surface of the colloids. Near-infrared fluorescence microscopy demonstrates the interfacial band-gap fluorescence of these SWNT-coated particles, suggesting potential routes to novel platforms and applications.