- Spectroscopy of CH3CO(-) and CH3CO
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We have measured the photoelectron spectra of CH3CO(-) and CH2DCO(-) and find the following electron affinities: EA(CH3CO) = 0.423 +/- 0.037 eV and EA(CH2DCO) = 0.418 +/- 0.038 eV.The spectra show excitation the C-C-O bending vibration of the radical, and we have measured the following bending frequencies: ν11(CH3CO) = 490 +/- 30 cm-1, ν11(CH2DCO) = 500 +/- 50 cm-1, and ν11(CH3CO(-)) = 570 +/- 180 cm-1.From a Franck-Condon analysis of the vibronic peak intensities we have estimated these C-C-O bond angles for the acetyl anion and radical:α(CCO) = 110 +/- 50 and α(CCO) = 133 +/- 50.These angles are consistent with ab initio Hartree-Fock geometry optimizations of both the ion and radical (in a triple-ζ plus polarization basis set).Finally, the electron affinities we have measured can be used to determine the following thermodynamic parameters: ΔHf0298(CH3CO) = -5.4 +/- 2.1 kcal/mol, ΔHf0298(CH3CO(-)) = -14.9 +/- 2.3 kcal/mol, DH298(CH3-CO) = 10.6 +/- 2.2 kcal/mol, and DH298((-)CH3-CO) = 17.6 +/- 2.3 kcal/mol.
- Nimlos, Mark R.,Soderquist, J. A.,Ellison, G. Barney
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- Gas-phase Carbanion Rearrangements. Does the Wittig Rearrangement occur for Deprotonated Vinyl ethers?
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Deprotonation of alkyl vinyl ethers (CH2=CHOR) with NH2- in the gas phase yields the two carbanions CH2=C(-)OR and C(-)H=CHOR.The former ion can be synthesized specifically using the SN2(Si) reaction CH2=C(SiMe3)OR + NH2- --> CH2=C(-)OR + Me3SiNH2: the ion undergoes several competitive and characteristic collision-induced reactions.For example, (i) when R >/= Et, elimination of an alkene, i.e.CH2=C(-)OR --> (CH2CHO)- + R-H, and (ii) the Wittig rearrangement CH2=C(-)OR --> CH2=C(R)O-.
- Eichinger, Peter C.H.,Bowie, John H.
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- ALPHA CARBOCATION STABILIZATION BY SILICON, GERMANIUM AND TIN
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The hydrolyses of a number of α-metalloidal vinyl ethers were found to undergo a ratel-imiting protonation to produce α- silil, germyl or stannyl carbocations.Comparative rate data leads to the ordering: C>Sn>Ge>Si>H, for the stabilization of such intermediates.
- Soderquist, John A.,Hassner, Alfred
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p. 1899 - 1902
(2007/10/02)
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