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Volumn 15, Issue 44, 2009, Pages 11815-11819

Isotope-sensitive degenerate [1,3]-hydrogen migration versus competitive enol-keto tautomerization

Author keywords

Hydrogen migration; Isotope effects; Keto enol tautomerism; Nonergodic behavior; Reaction mechanisms

Indexed keywords

CATION-RADICALS; DISSOCIATIVE IONIZATION; ELECTRON IONIZATION; HYDROGEN MIGRATION; ISOTOPE EFFECT; ISOTOPOLOGUES; KETO-ENOL TAUTOMERISM; LABORATORY PROCEDURES; LEWIS STRUCTURE; NATURAL BOND ORBITAL; NATURAL RESONANCE; OUT-OF-PLANE; P-TYPE; RADICAL CATIONS; REACTION MECHANISM; TAUTOMERIZATIONS; TRANSITION PATHWAY; UNIMOLECULAR DISSOCIATION;

EID: 73249151656     PISSN: 09476539     EISSN: 15213765     Source Type: Journal    
DOI: 10.1002/chem.200902176     Document Type: Article
Times cited : (6)

References (71)
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    • note
    • The mass spectrometric experiments were performed by using a modified VG instruments ZAB mass spectrometer; this is a four sector BEBE instrument whose performance has been described in detail previously. Briefly, enol cation radicals were generated by 70 eV dissociative ionization (McLafferty-type g-hydrogen rearrangement) of appropriately labeled 2-hexanones, the relevant enol ions 1-1i were mass-selected by B(1)E(1) and their unimolecular dissociations recorded by scanning B(2). The labeled 2-hexanones were synthesized by standard laboratory procedures, purified by preparative gas chromatography, and characterized by spectroscopic means. Particular attention was paid to the integrity of the labeling in the 2-hexanones deuterated in the a-and a'-positions because keto-enol tautomerization may lead to scrambling during workup. However, detailed 1H NMR analysis revealed >98% recovery of the labels in the original a-and a'-positions.
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    • Frisch, M.J.1    Trucks, G.W.2    Schlegel, H.B.3    Scuseria, G.E.4    Robb, M.A.5    Cheeseman, J.R.6
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    • note
    • Frequency calculations were carried out for all optimized structures with the same method to confirm the nature of the stationary point on the PES and to obtain the zero-point energies (ZPE) as well as to estimate the isotope effects. Relative energies (corrected for ZPE) are reported in kcalmol1. Intrinsic reaction coordinate calculations were performed to follow the reaction pathway and link transition structures (TS) with the respective intermediates. In the CAS calculations, the three 2pz orbitals of the carbon atoms, the 2pz and 2px orbitals of oxygen, and the two 1s orbitals of the two hydrogen atoms which are involved in migration were selected as the active orbitals.
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    • for examples of gas-phase analogues, see:
    • for examples of gas-phase analogues, see: (g) U. Dreyer, D. S'lzle, D. Schrçder, H. Schwarz, Helv. Chim. Acta 1990, 73, 2179;
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    • note
    • Note that for the only other [O-D]-labeled compound studied (1e), occurrence of the degenerate rearrangement is "invisible" in the mass spectrometric experiments because the resulting ions are identical, that is, CH3C(OD)CH2C+ ! CH2C(OD)CH3C+.


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.