International journal of mass spectrometry and ion processes vol:137 pages:93-106
date:UNIV PARIS 11,LURE,F-91405 ORSAY,FRANCE; UNIV PARIS 11,PHYSICOCHIM RAYONNEMENTS LAB,F-91405 ORSAY,FRANCE; UNIV LOUVAIN,DEPT CHEM,B-3001 LOUVAIN,BELGIUM
Dissociative ionization of cyclobutanol, 1 and cyclobutylamine, 2 to produce [CH2=CHX](.+) + C2H4 (X=OH Or NH2) has been studied by photoionization and ab initio molecular orbital calculations. The latter reveal that ionized cyclobutanol and cyclobutylamine are not minimia in their 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 onset, 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 mol(-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 combining calculations (at the MP2/6-311G**//UHF/6-31G* + ZPE level) and experiments, heats of formation of the distonic ions have been estimated: Delta H-f,300(0)[CH2CH2CH2CHOH](.+) = 733 kJ mol(-1) and Delta H-f,300(0)[CH2CH2CH2CHNH2](.+) = 792 kJ mol(-1), with a probable error of +/-12 kJ mol(-1).