A PHOTOIONIZATION AND MOLECULAR-ORBITAL STUDY OF CYCLOBUTANOL AND CYCLOBUTYLAMINE RADICAL CATIONS

Dissociative ionization of cyclobutanol, 1 and cyclobutylamine, 2 to p roduce [CH2=CHX](.+) + C2H4 (X=OH Or NH2) has been studied by photoion ization and ab initio molecular orbital calculations. The latter revea l that ionized cyclobutanol and cyclobutylamine are not minimia in the ir respective potential energy surfaces. It is further concluded that ionization of 1 and 2 leads to the corresponding distonic species [CH( 2)CH(2)CH(2)CHX](.+). From the measurement of the first dissociation o nset, an accurate determination of the heats of formation of [CH2=CHX] (.+) ions is made, i.e. Delta H-f,300(0)[CH2=CHOH](.+) = 768+/-5 kJ mo l(-1) and Delta H-f,300(0)[CH2=CHNH2](.+) = 838+/-5 kJ mol(-1), after correction for the thermal energy of the precursor molecules. By combi ning calculations (at the MP2/6-311G*//UHF/6-31G* + ZPE level) and ex periments, heats of formation of the distonic ions have been estimated : Delta H-f,300(0)[CH2CH2CH2CHOH](.+) = 733 kJ mol(-1) and Delta H-f,3 00(0)[CH2CH2CH2CHNH2](.+) = 792 kJ mol(-1), with a probable error of /-12 kJ mol(-1).