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Volumn 130, Issue 14, 2008, Pages 4934-4944

Proton transfers in aromatic and antiaromatic systems. How aromatic or antiaromatic is the transition state? An ab initio study

Author keywords

[No Author keywords available]

Indexed keywords

AROMATIC COMPOUNDS; BENZENE; CARBON; GEOMETRY; PARAMETER ESTIMATION;

EID: 41849151516     PISSN: 00027863     EISSN: None     Source Type: Journal    
DOI: 10.1021/ja078185y     Document Type: Article
Times cited : (18)

References (107)
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    • 2,3
    • 2,3
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    • Computational results in the gas phase have generally confirmed the presence of transition-state imbalances in these reactions11-16 although other factors such as field and polarizability effects often offset the π-acceptor effect on the intrinsic barriers.13c,d
    • 13c,d
  • 38
    • 41849084829 scopus 로고    scopus 로고
    • As corollary, a reactant stabilizing factor mat is lost ahead of bond changes increases the intrinsic barrier, whereas a reactant stabilizing factor that it lost late reduces the intrinsic barrier. For product and reactant destabilizing factors, the opposite relationships hold
    • As corollary, a reactant stabilizing factor mat is lost ahead of bond changes increases the intrinsic barrier, whereas a reactant stabilizing factor that it lost late reduces the intrinsic barrier. For product and reactant destabilizing factors, the opposite relationships hold.
  • 50
    • 41849112009 scopus 로고    scopus 로고
    • See the paragraph concerning the Supporting Information at the end of this article
    • See the paragraph concerning the Supporting Information at the end of this article.
  • 58
    • 41849092212 scopus 로고    scopus 로고
    • + (1.109 Å), but here the reduction is not as large as that for the transition state. The unusually short transition-state C-H bond length may be related to the C-H-C angle of less than 180° discussed earlier; the alternative transition state with a 180° angle mentioned above has a C-H bond length of 1.395 Å.
    • + (1.109 Å), but here the reduction is not as large as that for the transition state. The unusually short transition-state C-H bond length may be related to the C-H-C angle of less than 180° discussed earlier; the alternative transition state with a 180° angle mentioned above has a C-H bond length of 1.395 Å.
  • 62
    • 41849147524 scopus 로고    scopus 로고
    • The cyclobutenyl cation is known to be homoaromatic.38,39
    • 38,39
  • 65
    • 27744467698 scopus 로고    scopus 로고
    • 3-hybridized atoms see Raczynska, E. D.; Kosinska, W.; Osmialowski, B1; Gawinecki, R. Chem. Rev. 2005, 105, 3561.
    • 3-hybridized atoms see Raczynska, E. D.; Kosinska, W.; Osmialowski, B1; Gawinecki, R. Chem. Rev. 2005, 105, 3561.
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    • The percentages for a given system are not identical because each index measures a different property and thus cannot be expected to respond to aromaticity or antiaromaticity in exactly the same manner. What is important is that for eqs 7a and 8a the percentages are >50 while for eq 9a they are <50
    • The percentages for a given system are not identical because each index measures a different property and thus cannot be expected to respond to aromaticity or antiaromaticity in exactly the same manner. What is important is that for eqs 7a and 8a the percentages are >50 while for eq 9a they are <50%.
  • 67
    • 41849110553 scopus 로고    scopus 로고
    • Experimental43 as well as recent computational estimates 35,36 of the homoaromatic stabilization energy range from 7-9 kcal/mol
    • 35,36 of the homoaromatic stabilization energy range from 7-9 kcal/mol.
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    • 41849114164 scopus 로고    scopus 로고
    • Wheland, G. W. Resonance in Organic Chemistry; Wiley: New York, 1955; (a) p 517,
    • Wheland, G. W. Resonance in Organic Chemistry; Wiley: New York, 1955; (a) p 517,
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    • Table 3.7, p 98
    • (b) Table 3.7, p 98.
  • 83
    • 41849138644 scopus 로고    scopus 로고
    • In the cyclic systems, the reaction centers are secondary carbons, whereas in the noncyclic systems they are primary carbons
    • In the cyclic systems, the reaction centers are secondary carbons, whereas in the noncyclic systems they are primary carbons.
  • 84
    • 41849150051 scopus 로고    scopus 로고
    • On the basis of rate constant ratios for the deprotonation of CH 3CH2NO2 versus CH3NO 257 and (CO)5Cr=C(OMe)CH2CH 3 versus (CO)5Cr=C(OMe)-CH358 by OH- and piperidine
    • - and piperidine.
  • 87
    • 41849147167 scopus 로고    scopus 로고
    • This contrasts with the overall charges on the entire halves of the respective transition states, which, as pointed out above, are positive when the proton donor is cationic but negative when it is a neutral molecule
    • This contrasts with the overall charges on the entire halves of the respective transition states, which, as pointed out above, are positive when the proton donor is cationic but negative when it is a neutral molecule.
  • 88
    • 41849115972 scopus 로고    scopus 로고
    • In applying eq 15 to the calculation of n, we use me following definitions: δC is the difference between the charge on the reaction center of the transition state, 0.275) and the charge on the same center in the reactant, 0.001, chart 2, δY is the difference between the charge on the molecular skeleton excluding the reaction center of the transition state, 0.413) and the charge on the skeleton of the reactant proton donor (0.001, χ is the difference between the charge on the molecular skeleton excluding the reaction center of the product, 0.800) and the charge on the same skeleton of the reactant 0.001
    • Y is the difference between the charge on the molecular skeleton excluding the reaction center of the transition state (-0.413) and the charge on the skeleton of the reactant proton donor (0.001); χ is the difference between the charge on the molecular skeleton excluding the reaction center of the product (-0.800) and the charge on the same skeleton of the reactant (0.001).
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    • Personal communication
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    • For other examples, see ref 25
    • For other examples, see ref 25.
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    • Frisch, M. J. et al. Gaussian 98, Revision a.7.
    • Frisch, M. J. et al. Gaussian 98, Revision a.7.
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    • Frisch, M. J. et al. Gaussian 03, Revision D.01.
    • Frisch, M. J. et al. Gaussian 03, Revision D.01.


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.