A photoionization study of hydroperoxyl radical, HO{sub 2}; and hydrogen peroxide, H{sub 2}O{sub 2}

• Published in: Journal of electron spectroscopy and related phenomena Vol. 97; no. 1998
• Main Authors: Litorja, M., Ruscic, B., Chemistry
• Format: Journal Article
• Language: English
• Published: United States 01.01.1998
• Subjects: 08 HYDROGEN; DISSOCIATION ENERGY; FORMATION HEAT; HIGH-FREQUENCY DISCHARGES; HYDROGEN; HYDROGEN PEROXIDE; MASS SPECTROSCOPY; RADICALS
• ISSN: 0368-2048; 1873-2526
• DOI: 10.1016/S0368-2048(98)00264-3

Hydrogen peroxide and the hydroperoxyl radical have been studied by photoionization mass spectrometry. The radical has been produced in situ from H{sub 2}O{sub 2} by hydrogen abstraction with fluorine atoms produced in a microwave discharge. The adiabatic ionization energy of the hydroperoxyl radical has been measured as IE(HO{sub 2})=11.352{+-}0.007 eV, while that of hydrogen peroxide has been determined to be IE(H{sub 2}O{sub 2})=10.631{+-}0.007 eV. The OH{sup +} and HO{sub 2}{sup +} fragments from H{sub 2}O{sub 2} were also measured and their threshold behavior was analyzed in terms of model functions. The 0 K appearance energy of the HO{sub 2}{sup +} fragment was determined to be AE{sub 0}(HO{sub 2}{sup +}/H{sub 2}O{sub 2})=15.112{+-}0.035 eV. From these values, the O-H bond dissociation energy in hydrogen peroxide of D{sub 0}(H-OOH)=86.7{+-}0.8 kcal mol{sup -1} (87.9{+-}0.8 kcal mol{sup -1} at 298 K) was determined, yielding the enthalpy of formation of the hydroperoxyl radical of {Delta}Hf{sub 0}{circle_minus}(HO2)=4.0{+-}0.8 kcal mol-1 (3.3{+-}0.8 kcal mol-1 at 298 K), and also implying the proton affinity of oxygen of PA(O2)=100.6{+-}0.8 kcal mol{sup -1} and the enthalpy of deprotonation of hydrogen peroxide of {Delta}H{sub acid 298}{circle_minus}(H{sub 2}O{sub 2})=376.4{+-}0.8 kcal mol{sup -1}