The dissociation onset for halogen atom loss was investigated for 2-iodo and 2-chloropropane ions using a newly developed threshold photoelectron photoion coincidence (TPEPICO) technique that suppresses the effects of hot electrons. This study was undertaken in order to resolve current discrepancies concerning these onsets in the literature. The 0 K dissociation thresholds were determined to be 9.818 ± 0.010 and 11.036 ± 0.010 eV for 2-C3H7I and 2-C3H7Cl, respectively. These numbers agree quite well with photoionization and a mass analyzed threshold ionization (MATI) study, but are significantly lower than onsets measured by the much higher resolution pulsed field ionization PEPICO method. The derived C3H7+ heat of formation at 298 K is 803.9 ± 1.5 kJ mol−1, and a more precise value for the 298 K 2-iodopropane heat of formation is −40.8 ± 1.3 kJ mol−1. The derived proton affinity of propene is 746.1 kJ mol−1. We have also performed a high-level ab initio calculation on the 0 K dissociation limit, E0, for C3H7+ from C3H7Cl at the CCSD(T)/CBS level of theory with high-level corrections. The theoretical prediction of 11.048–11.061 eV for E0 (C3H7+) from C3H7Cl is found to be consistent with the current experimental value.
TraegerJ.C., “Photoionization Mass Spectrometry of the Propyl Halides”, Int. J. Mass Spectrom. Ion. Phys.32, 309 (1980).
2.
RosenstockH.M.BuffR.FerreiraM.A.A.LiasS.G.ParrA.C.StockbauerR.HolmesJ.L., “Fragmentation mechanism and energetics of some alkyl halide ions”, J. Am. Chem. Soc.104, 2337 (1982).
3.
BaerT.SongY.NgC.Y.LiuJ.ChenW., “The heat of formation of 2-C3H7+ and the proton affinity of C3H6 determined by pulsed field ionization - photoelectron photoion coincidence spectroscopy”, J. Phys. Chem. A104, 1959 (2000).
4.
ParkS.T.KimS.K.KimM.S., “One-photon mass-analyzed threshold spectroscopy of 1- and 2-iodopropanes in vacuum ultraviolet”, J. Chem. Phys.114, 5568 (2001).
5.
HunterE.P.LiasS.G., “Proton Affinity Evaluations”, in NIST Chemistry WebBook: NIST Standard Reference Databas 69.National Institute of Standards and Technology, Gaithersburg, MD 20899, USAhttp://webbook.nist.gov, (1998).
6.
HunterE.P.L.LiasS.G., “Evaluated Gas Phase Basicities and Proton Affinities of Molecules: An Update”, J. Phys. Chem. Ref. Data27, 413 (1998).
7.
SzulejkoJ.E.McMahonT.B., “Progress toward an absolute gas phase proton affinity scale”, J. Am. Chem. Soc.115, 7839 (1993).
8.
Meot-NerM., “The proton affinity scale, and effects of ion structure and salvation”, Int. J. Mass Spectrom.227, 525 (2003).
9.
BaerT., “Ion dissociation dynamics and thermochemistry by photoelectron photoion coincidence (PEPICO) spectrometry”, Int. J. Mass Spectrom.204, (2000).
10.
JarvisG.K.WeitzelK.M.MalowM.BaerT.SongY.NgC.Y., “High Resolution pulsed field ionization photoelectron photoion coincidence spectroscopy using synchrotron radiation”, Rev. Sci. Instrum.70, 3892 (1999).
11.
ParkS.T.KimS.K.KimM.S., “Vacuum-ultraviolet mass analyzed threshold ionization spectra of iodobutane isomers: Conformer-specific ionization and ion-core dissociation followed by ionization”, J. Chem. Phys.115, 2492 (2001).
12.
RuscicB.BerkowitzJ., “The H-NCS bond energy, heats of formation of HNCS, NCS, and IP of NCS from photoionziation mass spectrometric studies of HNCS, NCS, and (NCS)2”, J. Chem. Phys.101, 7975 (1994).
13.
TraegerJ.C.McLoughlinR.G.NicholsonA.J.C., “Heat of formation for acetyl cations in the gas phase”, J. Am. Chem. Soc.104, 5318 (1982).
14.
HofsteinJ.D.JohnsonP.M., “MATI and PIRI studies of the X∼ and A∼ state of trans-1,3-butadiene cation”, Chem. Phys. Lett.316, 229 (2000).
15.
TraegerJ.C.KompeB.M., Thermochemical data for free radicals from studies of ions, in Energetics of Organic Free Radicals, Ed by SimõesJ.A. MartinhoGreenbergA., Chapman & Hall, London, UK, pp. 59–109 (1996).
16.
BaerT.LiY., “Threshold Photoelectron Spectroscopy with Velocity Focusing: An Ideal Match for Coincidence Studies”, Int. J. Mass Spectrom.219, 381 (2002).
17.
SztárayB.BaerT., “The suppression of hot electrons in threshold photoelectron photoion coincidence spectroscopy using velocity focusing optics”, Rev. Sci. Instrum.74, 3763 (2003).
18.
QianX.M.LauK.C.NgC.Y., “A high-Resolution pulsed field ionization-photoelectron-photoion coincidence study of vinyl bromide”, J. Chem. Phys.120, 11031 (2004).
19.
WooH.K.LauK.C.NgC.Y., “Vibrational spectroscopy of trichloroethene cation by vacuum ultraviolet pulsed field ionization-photoelectron method”, Chinese J. Chem. Phys.17, 292 (2004).
20.
WooH.K.WangP.LauK.C.XingX.NgC.Y., “Singlephoton vacuum-ultraviolet laser-pulsed-field ionization-photoelectron studies of trans- and cis-1-bromopropenes”, J. Chem. Phys.120, 9561 (2004).
21.
WooH.K.ZhangJ.LauK.C.NgC.Y., “Vacuum ultraviolet laser pulsed field ionization photoelectron study of cis-2-butene”, J. Chem. Phys.116, 8803 (2002).
22.
WooH.K.LauK.C.ZhanJ.NgC.Y.LiC.L.LiW.K.JohnsonP.M., “Vacuum ultraviolet laser pulsed field ionization photoelectron study of trans-2-butene”, J. Chem. Phys.119, 7789 (2003).
23.
WooH.K.WangP.LauK.C.XingX.NgC.Y., “VUVpulsed field ionization andVUV-IR photo-induced Rydberg ionization study of trans-dichloroethane”, J. Phys. Chem. A108, in press (2004).
24.
DunningT.H.JrPetersonK.A.WoonD.E., in Encyclopedia of Computational Chemistry, Ed by SchleyerR.v.R., John Wiley & Sons, New York, USA, p. 88 (1998).
25.
FoglemanE.A.KoizumiH.KercherJ.P.SztárayB.BaerT., “The Heats of Formation of the Acetyl radical and Ion obtained by Threshold Photoelectron Photoion Coincidence”, J. Phys. Chem. A108, 5288 (2004).
26.
DunningT.H.Jr, “Gaussian basis sets for use in correlated molecular calculations. I. The atoms boron through neon and hydrogen”, J. Chem. Phys, 90, 1007 (1989).
27.
DunningT.H.JrPetersonK.A.WilsonA.K., “Gaussian basis sets for use in correlated molecular calculations. X. The atoms aluminum through argon revisited”, J. Chem. Phys.114, 9244 (2001).
28.
KendallR.A.DunningT.H.JrHarrisonR.J., “Electron affinities of the first-row atoms revisited. Systematic basis sets and wave functions”J. Chem. Phys.96, 6796 (1992).
29.
PetersonK.A.WoonD.E.DunningT.H.Jr, “Benchmark calculations with correlated molecular wave functions. IV. The classical barrier height of the H + H2 → H2 + H reaction”, J. Chem. Phys.100, 7410 (1994).
30.
PetersonK.A.DunningT.H.Jr, Accurate correlation consistent basis sets for molecular core-valence correlation effects: The second row atoms Al–Ar, and the first row atoms B-Ne revisited. J. Chem. Phys.117, 10548 (2002).
31.
WoonD.E.DunningT.H.Jr, “Gaussian basis sets for use in correlated molecular calculations V. Core-valence basis sets for boron through neon”, J. Chem. Phys.103, 4572 (1995).
32.
DavidsonE.R.IshikawaY.MalliG.L., “Validity of first-order perturbation theory for relativistic energy corrections”, Chem. Phys. Lett.84, 226 (1981).
33.
MooreC.E., “Atomic energy levels as derived from the analyses of optical spectra”, US Natl. But. Standards Circ.467, 1 (1949).
34.
MOLPRO. MOLPRO is a package of ab initio programs written by WernerH.-J.KnowlesP. J.SchützM.LindhR.CelaniP.KoronaT.RauhutG.ManbyF. R.AmosR. D.BernhardssonA.BerningA.CooperD. L.DeeganM. J. O.DobbynA. J.EckertF.HampelC.HetzerG.LloydA. W.McNicholasS. J.MeyerW.MuraM. E.NicklaßA.PalmieriP.PitzerR.SchumannU.StollH.StoneA. J.TarroniR.ThorsteinssonT. (2004).
35.
FrischM.J.TrucksG.W.SchlegelH.B.ScuseriaG.E.RobbM.A.CheesemanJ.R.MontgomeryJ.A.VrevenT.KudinK.N.BurantJ.C.MillamJ.M.IyengarS.S.TomasiJ.BaroneV.MennucciB.CossiM.ScalmaniG.RegaN.PeterssonG.A.NakatsujiH.HadaM.EharaM.ToyotaK.FukudaR.HasegawaJ.IshidaM.NakajimaT.HondaY.KitaoO.NakaiH.KleneM.LiX.KnoxJ.E.HratchianH.P.CrossJ.B.AdamoC.JaramilloJ.GompertsR.StratmannF.YazyevO.AustinA.J.CammiR.PomelliC.OchterskiJ.W.AyalaP.Y.MorokumaK.VothG.A.SalvadorP.DannenbergJ.J.ZakrzewskiV.G.DapprichS.DanielsA.D.StrainM.C.FarkasÖ.MalickD.K.RabuckA.D.RaghavachariK.ForesmanJ.B.OrtizJ.V.CuiQ.BaboulA.G.CliffordS.CioslowskiJ.LiuB.B.StefanovG.LiashenkoA.PiskorzP.KomáromiI.MartinR.L.FoxD.J.KeithT.Al-LahamM.A.PengC.Y.NanayakkaraA.ChallacombeM.GillP.M.W.JohnsonB.ChenW.WongM.W.GonzalezC.PopleJ.A., Gaussian 03, Revision A1.Gaussian, Inc.Pittsburgh, PA, USA (2004).
36.
KimuraK.KatsumataS.AchibaY.YamazakiT.IwataS., Handbook of He(I) Photoelectron Spectra of Fundamental Organic Molecules.Halsted Press, New York, USA (1981).
37.
ChewterL.A.SanderM.Muller-DethlefsK.SchlagE.W., “High Resolution zero kinetic energy photoelectron spectroscopy of benzene and determination of the ionization potential”, J. Chem. Phys.86, 4737 (1987).
38.
ChupkaW.A., “Factors affecting lifetimes and Resolution of Rydberg states observed in zero-electron kinetic-energy spectroscopy”, J. Chem. Phys.98, 4520 (1993).
39.
WeitzelK.M.JarvisG.K.MalowM.BaerT.SongY.NgC.Y., “Observation of Accurate Ion Dissociation Thresholds in Pulsed Field Ionization Photoelectron Studies”, Phys. Rev. Lett.86, 3526 (2001).
40.
NgC.Y., “Vacuum Ultraviolet Spectroscopy and Chemistry Using Photoionization and Photoelectron Methods”Ann. Rev. Phys. Chem.53, 101 (2002).
41.
LagoA.F.BaerT.NgC.Y.QianX.-M., Unpublished work from the Baer and Ng groups (2004).
42.
PedleyJ.B.NaylorR.D.KirbyS.P., Thermochemical Data of Organic Compounds, 2nd Edn.Chapman and Hall, London, UK (1986).
43.
PedleyJ.B., Thermochemical Data and Structures of Organic Compounds.Thermodynamics Research Center, College Station, Texas, USA (1994).
44.
TraegerJ.C.McLoughlinR.G., “Absolute heats of formation for gas phase cations”, J. Am. Chem. Soc.103, 3647 (1981).
