A mass spectrometric and computational study of gaseous peroxynitric acid and (HOONO2)H+ protomers1 Authors: Aschi, Massimilianoa; Attina`, Marinab; Cacace, Fulvioa; Cartoni, Antonellab; Pepi, Federicoa Affiliations: a. Dipartimento di Studi di Chimica e Tecnologia delle Sostanze Biologicamente Attive, Universita' di Roma "La Sapienza," P.le A. Moro 5, I-00185, Roma, Italy

b. Dipartimento di Scienze e Tecnologie Chimiche, Universita' di Roma "Tor Vergata" Via della Ricerca Scientifica 1, I-00133, Roma, Italy Keywords: Peroxides; Gas-phase chemistry; Mass spectrometry; Ab initio and DFT calculations; Ion-neutral complexes

Abstract (English):

FULL TEXT

The positive ion chemistry of peroxynitric acid (1) was investigated in the gas phase by mass-analyzed ion kinetic, collisionally activated dissociation, and Fourier transform-ion cyclotron resonance mass spectrometric techniques and theoretical methods up to the B3LYP/6-311++g(3df,2pd) and G2, i.e. QCISD(T)/6-311+g(3df,2pd), levels. The ion-neutral complex HOOH-NO2+ (1a) is the only detectable protomer in CI experiments involving the protonation of 1 by H3O+, and can also be obtained from the reaction of NO2+ with H2O2. 1a behaves as a protonating and nitrating agent toward gaseous nucleophiles. The experimental proton affinity of 1 is estimated to be 176 ? 3 kcal mol-1, in excellent agreement with the 175 ? 2 kcal mol-1 G2 PA. The theoretical results show that 1a is more stable than the HOONO2H+ (1b) and the H2OONO2+ (1c) protomers by 13 and 16 kcal mol-1, respectively, at the B3LYP level of theory, and account for the exclusive formation of 1a in the CI experiments. The experimental and B3LYP theoretical binding energy of NO2+ to H2O2 amounts to 18 ? 2 kcal mol-1.