- Gas-phase basicity and acidity trends in α,β-unsaturated amines, phosphines, and arsines
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The acidity and basicity trends in the series of α,β-unsaturated amines, phosphines, and arsines were analyzed through the use of G2 ab initio calculations and the examination of experimental data obtained by means of FT-ICR techniques. The α,β-unsaturated amines, phosphines, and arsines are less basic but significantly more acidic than the corresponding saturated analogues. However, while both vinyl- and ethynylamine protonate preferentially at the β-carbon atom, vinyl- and ethynylphosphine are phosphorus bases in the gas-phase. Arsines resemble closely the corresponding phosphines, although protonation at the Ca atom competes with protonation at the heteroatom. The enhanced acidity of unsaturated compounds can be attributed essentially to a stabilization of the anions because of a favorable interaction of the XH- group with the C-C multiple bonds. This stabilizing effect is maximum for amines and minimum for arsines. The low relative basicity of these unsaturated compounds results from a destabilization of the protonated species due to unfavorable interactions of the XH3+ group with the C-C π-system. Protonation at the β-carbon is strongly favored for amines but unfavorable for phosphines and arsines, because the carbocation formed is much less stabilized when the heteroatom of the XH2 group belongs to the second or the third-row than when it is a first-row atom.
- Mó, Otilia,Yá?ez, Manuel,Decouzon, Michèle,Gal, Jean-Fran?ois,Maria, Pierre-Charles,Guillemin, Jean-Claude
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p. 4653 - 4663
(2007/10/03)
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- Polyamino salts of alpha-hydroxyacids, alpha-ketoacids and related compounds
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Cosmetic compositions are described wherein α-hydroxyacids, α-ketoacids and related compounds are formed into amine salts through neutralization with a multi-amine functionalized polymer. Particularly preferred are glycolic acid and lactic acid salts of poly(ethylenimine).
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- Reversal of electronic Substituent Effects in the Retro-Diels-Alder Reaction. A Charge Neutral Analogue of Oxyanion-Accelerated Cycloreversion
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The retro-Diels-Alder reaction of anthracene cycloadducts is influenced by the dienophile substituents in the following ways: (1) electron-withdrawing groups increase the rate of the reaction; (2) strongly conjugating substituents make the reaction much faster than predicted by classical electron-withdrawing or -donating ability, in the best case by a factor of 3 x 106, and (3) there is no observable steric effect, in contrast to literature statements to the contrary.
- Nanjappan, Palaniappan,Czarnik, Anthony W.
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p. 2851 - 2853
(2007/10/02)
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- Molecular Ions of TRansient Species: Vinylamine Cation
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Vinylamine 1 was prepared by thermolysis of cyclobutylamine and its photoelectron spectrum was measured.I1a = 8.20 eV and I1v = 8.65 eV were found, the dominant vinrational progression (ν = 725 cm-1) indicating that in the course of 1(X) -> 1+(X) flattening around the N-atom occurs.The Franck-Condon profile of this band, however, suggests that a skeletal mode of ν ca. 1400 cm-1 (observed also in the iso-?-electronic systems vinyl-alcohol-cation and allyl radical) may also be excited.Comparison with the data for the isomer acetaldehyde-imine 2 and its cation 2+ shows that the isomer couple 1/2 constitutes a further notable example for a relative thermochemical stability inversion on going from neutrals to the cations.
- Albrecht, Bruno,Allan, Michael,Haselbach, Edwin,Neuhaus, Louis
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p. 220 - 223
(2007/10/02)
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- REACTIONS RETRODIENIQUES-IX. SYNTHESE PAR THERMOLYSE ECLAIR ET ETUDE D'ENAMINES PRIMAIRES INSTABLES
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Etheneamine 1 and its methyl derivatives 2-7 have been synthesized from the adducts 8-14 by a retro-Diels-Alder reaction under flash thermolytic conditions.The primary enamines 1-4 have been identified (IR, (1)H and (13)C NMR in a pure state at -80 deg C; at the same temperature, the enamines 5-7, less stable, are already accompanied by their tautomeric imines 33 or 34.When warmed up to room temperature, the enamines 1-7 lead, following to their substitution, either to nitrogen heterocycles (30, 42) or to acyclic azadienes (35-37, 39, 40).
- Ripoll, J. L.,Lebrun, H.,Thuillier, A.
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p. 2497 - 2504
(2007/10/02)
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