Gas-Phase Ion−Molecule Reactions in C₃F₆

Abstract

6 ) n , respectively, become faster at lower temperature. This is due to the existence of an entropy barrier for the formation of cluster ions. The C 3 F 5 + ion was found to form cluster ions readily with C 3 F 6 solvent molecules. Thermochemical stabilities for C 3 F 5 + (C 3 F 6 ) n with n ) 1 and 2 could be determined. The proton affinity (PA) of C 3 F 6 was found to be smaller but close to that of C 2 H 4 (162.6 ( 1.5 kcal/mol). The G2MP2-calculated PA is 157.26 kcal/mol. Lone-pair orbitals of the CF 3 substituent are electronic-charge donor sites to C 2 F 4 + and C 3 F 5 + . The polymerization reactions of C 3 F 6 initiated by F -, C 3 F 5 -, and C 3 F 6were observed. Those reactions became faster with a decrease of temperature. The high reactivity of C 3 F 6 in the negative-mode ion/molecule reactions is ascribed to the perfluoro effect. The halide ions Cl -, Br -, and Iwere found to form cluster ions with C 3 F 6 . Thermochemical stabilities for X -(C 3 F 6 ) n (X -) Cl -, Br -, and I -) have been determined. A slight charge transfer in the complex Cl -fC 3 F 6 results in the fairly strong bond energy (12.6 kcal/mol) for the cluster.

VUV photoabsorption by hexafluoropropene

“…The adiabatic ionisation energy of CF 2 CFCF 3 has been determined by Cullen et al [15] and by Freiser and Beauchamp [16] to be 10.62 eV, corresponding to the removal of an electron from the p component of the C@C bond [17]. In analogy with tetrafluoroethylene (C 2 F 4 ) and considering the perfluoro effect [18], the HOMO is considered to be of p character along the C@C axis and the LUMO of C@C p* character [19].…”

Positive Ion/Molecule Reactions in Tetrafluoroethylene

“…The formation of CF 3 ῌ as one of the major ions is a very important information in the plasma chemistry because this ion is known to act as a very e$cient etchant in the semiconductor fabrication. (5).…”

12 Organic gas-phase ion chemistry

“…Additional reports include a study of the reactivity of alkyl cations with alkyl benzenes 13 and alcohols, 14 and a study of the reactivity of fluorinated alkyl cations and anions with fluoroalkanes. 15 Kuck has reviewed the scrambling reactions of organic cations and radical cations in the gas phase. 16…”

“…Ion and neutral properties can often be related by simple thermochemical cycles, such as those shown in eqns. ( 14) and (15). 87,88 Equation ( 14) provides a method for determining homolytic bond dissociation energies (BDEs) from negative ion thermochemical properties, gas-phase acidities (∆ acid H ) and electron affinities (EA), whereas in eqn.…”

“…87,88 Equation ( 14) provides a method for determining homolytic bond dissociation energies (BDEs) from negative ion thermochemical properties, gas-phase acidities (∆ acid H ) and electron affinities (EA), whereas in eqn. (15) the BDE is related to the ionization energy of the radical (IE) and the appearance energy (E AP ) for formation of the ion, R ϩ , from RH. Proper application of these equations requires careful consideration of the temperature dependence of the thermochemical properties.…”