Gas-phase positive and negative ion chemistry of methyl hydroperoxide
 Aschi, Massimiliano^a; Attinà, Marina^b; Cacace, Fulvio^a; Cipollini, Romano^a; Pepi, Federico

 a. Università ‘La Sapienza’, P.le A. Moro 5, 00185 Rome, Italy
b. Università ‘Tor Vergata’, Via della Ricerca Scientifica, 00133 Rome, Italy Keywords: Gas-phase chemistry; Organic hydroperoxides

FULL TEXT

Abstract

The gas-phase ion chemistry of methyl hydroperoxide (1) was investigated by mass spectrometric and theoretical methods. The proton affinity of 1, 173.3 ± 2 kcal mol^-1 measured by the FT-ICR bracketing technique and the kinetic method, is in excellent agreement with the value of 172.6 ± 2 kcal mol^-1 from G2 ab initio calculations, which identify the a oxygen atom as the most basic site. Methylation of 1 by (CH₃)₂F⁺ gives a mixed population of ions methylated at both oxygen atoms. The experimental proton affinity of CH₃OOCH₃ is 176.2 ± 4 kcal mol^-1, versus a theoretically computed value of 180.4 ± 2 kcal mol^-1, the most nucleophilic site being again the a oxygen atom. Nitrosation of 1 yields a (CH₃OOH·NO)⁺ adduct that behaves as both a nitrosating and a protonating agent. The results are discussed and compared with earlier pertinent studies.

Publisher: Elsevier Science