TY - JOUR
T1 - Evidence for orbital-specific electron transfer to oriented haloform molecules
AU - Jia, Beike
AU - Laib, Jonathan
AU - Lobo, R. F. M.
AU - Brooks, Philip R.
PY - 2002/11/20
Y1 - 2002/11/20
N2 - Beams of hyperthermal K atoms cross beams of the oriented haloforms CF3H, CCl3H, and CBr3H, and transfer of an electron mainly produces K+ and the X- halide ion which are detected in coincidence. As expected, the steric asymmetry of CCl3H and CBr3H is very small and the halogen end is more reactive. However, even though there are three potentially reactive centers on each molecule, the F- ion yield in CF3H is strongly dependent on orientation. At energies close to the threshold for ion-pair formation (∼5.5 eV), H-end attack is more reactive to form F-. As the energy is increased, the more productive end switches, and F-end attack dominates the reactivity. In CF3H near threshold the electron is apparently transferred to the σ*CH antibonding orbital, and small signals are observed from electrons and CF3- ions, indicating "activation" of this orbital. In CCl3H and CBr3H the steric asymmetry is very small, and signals from free electrons and CX3- ions are barely detectable, indicating that the σ*CH antibonding orbital is not activated. The electron is apparently transferred to the σcx* orbital which is believed to be the LUMO. At very low energies the proximity of the incipient ions probably determines whether salt molecules or ions are formed.
AB - Beams of hyperthermal K atoms cross beams of the oriented haloforms CF3H, CCl3H, and CBr3H, and transfer of an electron mainly produces K+ and the X- halide ion which are detected in coincidence. As expected, the steric asymmetry of CCl3H and CBr3H is very small and the halogen end is more reactive. However, even though there are three potentially reactive centers on each molecule, the F- ion yield in CF3H is strongly dependent on orientation. At energies close to the threshold for ion-pair formation (∼5.5 eV), H-end attack is more reactive to form F-. As the energy is increased, the more productive end switches, and F-end attack dominates the reactivity. In CF3H near threshold the electron is apparently transferred to the σ*CH antibonding orbital, and small signals are observed from electrons and CF3- ions, indicating "activation" of this orbital. In CCl3H and CBr3H the steric asymmetry is very small, and signals from free electrons and CX3- ions are barely detectable, indicating that the σ*CH antibonding orbital is not activated. The electron is apparently transferred to the σcx* orbital which is believed to be the LUMO. At very low energies the proximity of the incipient ions probably determines whether salt molecules or ions are formed.
UR - http://www.scopus.com/inward/record.url?scp=0037146036&partnerID=8YFLogxK
U2 - 10.1021/ja027710k
DO - 10.1021/ja027710k
M3 - Article
C2 - 12431121
AN - SCOPUS:0037146036
SN - 0002-7863
VL - 124
SP - 13896
EP - 13902
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 46
ER -