- Transformation of 1,3-, 1,4- and 1,5-diols over perfluorinated resinsulfonic acid (Nafion-H)
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The transformations of 1,3-, 1,4- and 1,5-diols over perfluorinated resinsulfonic acids (Nafion-H) were studied and correlations were examined between the structure of the investigated diols, the possible transformation directions and the catalytic properties of Nafion-H. Comparisons were also made between the catalytic properties of Nafion-H and zeolites. The characteristic transformations of 1,3-diols depend on their structure. 1,3-Propanediol undergoes dehydration via 1,2-elimination and yields oligomers via intermolecular dehydration. 1,3-Diols with an alkyl substituent on the carbon between those bearing the OH groups undergo 1,2-elimination yielding unsaturated alcohols and dienes, and give carbonyl compounds via the loss of water and hydride shifts analogous to the pinacol rearrangement. The strong acidity of Nafion-H and the lack of strong basic sites are advantageous for the latter reaction. 1,3-Diols with two substituents at this position mainly yield fragmentation products. Stereoselective cyclodehydration to the corresponding oxacycloalkanes is the characteristic transformation of 1,4- and 1,5-diols over Nafion-H.
- Bucsi,Molnar,Bartok,Olah
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p. 3319 - 3326
(2007/10/02)
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- Isomerisation des radicaux insatures. III. Radicaux α,α,β-, α,β,γ- et α,α,γ-trimethallyles
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α,α,β-, α,β,γ-, and α,α,γ-trimethallyl radicals have been generated in the 147.0-nm gas phase photolysis of 2,3,3-trimethyl-1-butene, 3,4-dimethyl-2-pentene, and 2,4-dimethyl-2-pentene, respectively.Under these conditions, the majority of allyl radicals have an internal energy sufficient for further decomposition: they give rise to the formation of various 1,3-dienes and small amounts of either 1,2- or 2,3-dienes.An internal sigmatropic 1,2-hydrogen atom transfer process is part of the proposed mechanism to explain such products.Moreover, the fragmentation of the trimethyl substituted allyl radicals involves the split of one β(C-C) bond, then one β(C-H), and, to a lesser extent, one central C-CH3 bond.
- Deslauriers, Helene,Collin, Guy J.
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p. 3168 - 3173
(2007/10/02)
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- Copper(I) Chemical Ionization-Mass Spectroscopic Analysis of Esters and Ketones
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The present work lays the foundation for the understanding and evaluation of atomic metal ions as a new class of chemical ionization reagent ions.In particular, a thorough study of the gas phase ion chemistry of Cu(1+), generated by laser ionization from the pure metal, with a series of oxygenated compounds is reported.Definite patterns of reactivity for different classes of oxygenated compounds are observed which, together with an understanding of the reaction mechanisms, provide the basis for predicting the Cu(1+) chemical ionization mass spectra of new compounds with analogous functional groups.The chemistry of Cu(1+) is found to be dramatically different from that of Ti(1+) and Li(1+) reported earlier providing a significant indication of the flexibility and selectivity afforded by atomic metal reagent ions.
- Burnier, R. C.,Byrd, G. D.,Freiser, B. S.
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p. 1641 - 1650
(2007/10/02)
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