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Volumn 73, Issue 11, 2008, Pages 4110-4115

A kinetic study of the reaction of N,N-dimethylanilines with 2,2-diphenyl-1-picrylhydrazyl Radical: A Concerted Proton-Electron Transfer?

Author keywords

[No Author keywords available]

Indexed keywords

CHARGED PARTICLES; CHEMICAL REACTIONS; CHEMICAL REACTIVITY; MICROFLUIDICS; PROTON TRANSFER;

EID: 44949107432     PISSN: 00223263     EISSN: None     Source Type: Journal    
DOI: 10.1021/jo8001672     Document Type: Article
Times cited : (28)

References (47)
  • 1
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    • Blois, M. S. Nature 1958, 181, 1199-1200.
    • (1958) Nature , vol.181 , pp. 1199-1200
    • Blois, M.S.1
  • 4
    • 44949206009 scopus 로고    scopus 로고
    • The transfer of a hydrogen atom formally involves the transfer of an electron and a proton. When electron and proton are transferred to the same center in the same step, we generally speak of HAT mechanism. Very recently, however, DFT theoretical calculations5-7 have shown that quite energetically different situations can arise depending on whether the same or different sets of orbitals are involved in the transfer of the proton and the electron. In the former case, the mechanism continues to be designated as HAT; in the latter case, the process is described as a proton coupled electron transfer (PCET) or a concerted proton electron transfer CPET, Theoretical calculations8 have also shown that both HAT and CPET pathways are possible for the reaction of dpph• with phenols. It should, however, be noted that Huynh and Meyer9 have expressed some reservation on the distinction discussed above. According to these authors, the C
    • 9 have expressed some reservation on the distinction discussed above. According to these authors, the CPET terminology should be strictly reserved to when proton and electron are transferred to orbitals located in well separated sites.
  • 24
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    • 17
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  • 25
    • 44949246923 scopus 로고    scopus 로고
    • In a more recent study, however, the reaction of N-Me-AcrH 2 with dpph• has been assumed to take place by a HAT mechanism.3
    • 3
  • 31
    • 44949110664 scopus 로고    scopus 로고
    • 28
    • 28
  • 33
    • 44949182388 scopus 로고    scopus 로고
    • The correlation was much worse using the Hammett σ constants
    • The correlation was much worse using the Hammett σ constants.
  • 35
    • 0004032955 scopus 로고
    • Kochi, J. K, Ed, John Wiley & Sons: New York, Chapter 7
    • Russell, G. A. In Free Radicals; Kochi, J. K., Ed.; John Wiley & Sons: New York, 1973; Vol. 1, Chapter 7.
    • (1973) Free Radicals , vol.1
    • Russell, G.A.1
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  • 40
    • 44949181388 scopus 로고    scopus 로고
    • It should be noted, however, that if deprotonation of the radical cation, eq 2 in Scheme 1, is carried out exclusively by dpph, no retarding effect by dpph- is expected in a preequilibrium ET mechanism. However, it is probable that substantial deprotonation by the solvent is also occurring in view of the extremely small concentration of dpph- at the equilibrium
    • - at the equilibrium.
  • 44
    • 44949251376 scopus 로고    scopus 로고
    • This appears to be a general outcome for reactions involving hydrogen transfer from a C-H bond. These processes are generally slightly faster in solvents of lower polarity even when the transition state has a polar character. Entropy compensation effects are probably at play.41
    • 41
  • 46
    • 44949232761 scopus 로고    scopus 로고
    • In the HAT transition state, a partial positive charge should develop on the methyl carbon, which should make it more difficult to rationalize the ρ value observed
    • In the HAT transition state, a partial positive charge should develop on the methyl carbon, which should make it more difficult to rationalize the ρ value observed.
  • 47
    • 44949144550 scopus 로고    scopus 로고
    • 2+ concentration and a reaction order of ca 0.3 was calculated (see Figure S6 in the Supporting Information).
    • 2+ concentration and a reaction order of ca 0.3 was calculated (see Figure S6 in the Supporting Information).


* 이 정보는 Elsevier사의 SCOPUS DB에서 KISTI가 분석하여 추출한 것입니다.