THE HEAT OF FORMATION OF THE [C-6,H-5,O](-OXAFULVALENE() ISOMERIC ION, PROTONATED 6)

The appearance energy of the alpha-C protonated 6-oxafulvalene, C5H5CO +, generated from the fragmentation of ionized (CO)(3)MnC5H4CHO (estim ated Delta H-f(0) of neutral complex -602 +/- kJ mol(-1)) gave a value of 705 +/- 30 kJ mol(-1) for its heat of formation. Further dissociat ion of this species by the loss of CO took place very close to the cal culated thermochemical threshold, confirming the formation of the cycl opentadienyl cation. The above result confirms the earlier estimated s tability of this [C-6,H-5,O](+) isomer relative to those of the phenox y and hydroxyphenyl cations. (C) 1997 Elsevier Science B.V.