TY - JOUR

T1 - Alkyl Radicals as Hydrogen Bond Acceptors: Computational Evidence

AU - Hammerum, Steen

PY - 2009

Y1 - 2009

N2 - Spectroscopic, energetic and structural information obtainedby DFT and G3-type computational studies demonstrates that chargedproton donors can form moderately strong hydrogen bonds to simplealkyl radicals. The presence of these bonds stabilizes the adductsand modifies their structure, and gives rise to pronounced shifts ofIR stretching frequencies and to increased absorption intensities. Thehydrogen bond acceptor properties of alkyl radicals equal those of manyconventional acceptors, e.g., the bond length changes and IR red-shiftssuggest that tert-butyl radicals are slightly better acceptors thanformaldehyde molecules, while propyl radicals are as good as H2O. Thehydrogen bond strength appears to depend on the proton affinity of theproton donor and on the ionization energy of the acceptor alkyl radical,not on the donor-acceptor proton affinity difference, reflecting that thecharge-transfer aspects of hydrogen bonding are particularly conspicuouswhen the acceptor polarity and basicity is low. Udgivelsesdato: 2 juni 2009

AB - Spectroscopic, energetic and structural information obtainedby DFT and G3-type computational studies demonstrates that chargedproton donors can form moderately strong hydrogen bonds to simplealkyl radicals. The presence of these bonds stabilizes the adductsand modifies their structure, and gives rise to pronounced shifts ofIR stretching frequencies and to increased absorption intensities. Thehydrogen bond acceptor properties of alkyl radicals equal those of manyconventional acceptors, e.g., the bond length changes and IR red-shiftssuggest that tert-butyl radicals are slightly better acceptors thanformaldehyde molecules, while propyl radicals are as good as H2O. Thehydrogen bond strength appears to depend on the proton affinity of theproton donor and on the ionization energy of the acceptor alkyl radical,not on the donor-acceptor proton affinity difference, reflecting that thecharge-transfer aspects of hydrogen bonding are particularly conspicuouswhen the acceptor polarity and basicity is low. Udgivelsesdato: 2 juni 2009

KW - Faculty of Science

U2 - 10.1021/ja901854t

DO - 10.1021/ja901854t

M3 - Journal article

C2 - 19489573

VL - 131

SP - 8627

EP - 8635

JO - Journal of the American Chemical Society

JF - Journal of the American Chemical Society

SN - 0002-7863

ER -