Dissociation dynamics of energy selected, propane, and i-C(3)H(7)X(+) Ions by iPEPICO: accurate heats of formation of i-C(3)H(7)(+), i-C(3)H(7)Cl, i-C(3)H(7)Br, and i-C(3)H(7)I.
The dissociation dynamics of energy selected i-C(3)H(7)X (X = H, Cl, Br, and I) ions have been investigated by imaging photoelectron-photoion coincidence (iPEPICO) spectroscopy using synchrotron radiation from the X04DB VUV beamline in the Swiss Light Source of the Paul Scherrer Institut. The 0 K dissociation energy (E(0)) for i-C(3)H(8) was determined to be 11.624 ± 0.002 eV. This leads to a 298 K isopropyl ion heat of formation of 805.9 ± 0.5 kJ mol(-1). The Δ(f)H(298K)°(i-C(3)H(7)(+)) combined with the measured 0 K onsets for i-C(3)H(7)(+) formation from isopropyl chloride (11.065 ± 0.004 eV), isopropyl bromide (10.454 ± 0.008 eV), and isopropyl iodide (9.812 ± 0.008 eV) yields the 298 K isopropyl chloride, bromide, and iodide heats of formation of -145.7 ± 0.7, -95.6 ± 0.9, and -38.5 ± 0.9 kJ mol(-1), respectively. These values provide a significant correction to literature values and reduce the error limits. Finally, the new i-C(3)H(7)(+) heat of formation leads to a predicted adiabatic ionization energy for the isopropyl radical of 7.430 ± 0.012 eV and a 298 K proton affinity for propene of 744.1 ± 0.8 kJ mol(-1).
Stevens
William R
WR
Department of Chemistry, University of North Carolina, Chapel Hill, North Carolina 27599-3290, USA.
Bodi
Andras
A
Baer
Tomas
T