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Gas-Phase Ion / Molecule Reactions in Octafluorocyclobutane
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Kiyotoshi TAKAO, Takayuki MIZUNO, Tomoyuki IINO, Fumiyuki NAKAGAWA, Hiroko SUYAMA, Kenzo HIRAOKA, and Shinichi YAMABE
a) Graduate School of Engineering, Yamanashi University (4-3-11 Takeda, Kofu 400-8511, Japan)
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Ion/molecule reactions in octafluorocyclobutane (c-C4F8) were studied using a high-pressure mass spectrometer. The thermochemical stabilities of the cluster ions of halide ions (X-) with c-C4F8 were measured. While the F- ion forms a covalent bond with c-C4F8, the interaction between other halide ions with c-C4F8 is mainly electrostatic. Theoretical calculation revealed that the halide ions interact not with the lowest unoccupied molecular orbital but with the next lowest unoccupied molecular orbital of the c-C4F8 molecule in the most stable cluster ions X- (c-C4F8). The electron affinity of c-C4F8 was measured to be 24.2±2.3 kcal/mol (1.05±0.10 eV) by observing the equilibria for reaction of SF6-+c-C4F8 = c-C4F8-+SF6- While the sound equilibrium for that reaction was established in the temperature region from  350 K down to the lowest temperature measured (150 K), that was not established in the higher temperature region above 350 K. This was attributed to the existence of an isomer for c-C4F8- whose electron detachment energy is smaller than 1.05 ev. By the measurement of thermochemical stabilitries of [(O2)m(c-C4F8)n]- (m+n = 1-3), the lower electron affinity of c-C4F8 was determined to be 12.0±1.2 kcal/mol (0.52±0.05 eV). The lower limit of the proton affinity of c-C4F8 was estimated to be 130 kcal/mol.
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Key words:
Octafluorocyclobutane, Clustering reactions,
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