Massimiliano
Aschia,
Felice Grandinetti
,
b
and Federico Pepia
aDipartimento di Chimica e Tecnologia delle
Sostanze Biologicamente Attive, Universita`di Roma “La Sapienza”,
P. le A. Moro, 5-00185 Rome, Italy
bDipartimento di
Scienze Ambientali, Universita`della Tuscia, Via S.C. De Lellis,
01100 Viterbo, Italy
Received 27 July 1993; revised 23
September 1993. Available online 10 January 2002.
NF+2 ions from the ionization of NF3 efficiently add to H2O (F2NOH)H+ under chemical ionization conditions. In keeping with the formation process employed, collisionally activated dissociation mass spectrometry indicates the exclusive formation of the oxygen-protonated isomer of F2NOH. Ab initio calculations, at thegaussian-1 level of theory, indicate that this ion is the least stable among the investigated (F2NOH)H+ isomers. However, it is trapped in a deep potential well, which prevents extensive isomerization to the nitrogen-protonated and to the fluorine-protonated isomers, the latter one being by far the most stable protomer. Thegaussian-1 potential energy profile accords well with the experimental features of the unimolecular decomposition of the (F2NOH2)+ ions, probed by mass analyzed ion kinetic energy (MIKE) spectrometry. Only the loss of HF was detected, characterized by a dish-topped peak in the MIKE spectrum. Consistent with the ab initio calculations, the measured kinetic energy release is as large as 1.36 eV. The emerging picture has been compared with the previously reported results concerning the gas-phase protonation of NF3.
Keywords: Nitrogen fluoride (NF3)/water; Protonated F2NOH; CAD mass spectrometry; MIKE spectrometry; gaussian-1 calculations