title: Enol formation and ring-opening in OH-initiated oxidation of cycloalkenes.
abstract: Photolytic OH-initiated oxidation of cyclopentene, cyclohexene, and 1,4-cyclohexadiene have been investigated by using tunable synchrotron photoionization mass spectrometry. Electronic structure calculations (CBS-QB3) are employed in Franck-Condon (FC) spectral simulations of the photoionization efficiency curves (PIE) of the observed products. Cyclopentenol (cyclopenten-1-ol, 1-c-C(5)H(7)OH) and its isomers cyclopenten-2-ol (2-c-C(5)H(7)OH) and cyclopentanone (c-C(5)H(8)=O), are detected from OH-initiated cyclopentene oxidation. The measured adiabatic ionization energy (AIE) of 1-c-C(5)H(7)OH is 8.4(+/-0.1) eV, and that of 2-c-C(5)H(7)OH is 9.5(+/-0.1) eV. The calculated AIE of possible cyclopentene oxidation products cis-1,2-epoxycyclopentane and 2,3-epoxycyclopentanol is 9.97 and 9.44 eV, respectively. Product spectra from OH-initiated oxidation of cyclohexene and cyclohexa-1,4-diene show a substantial contribution from linear aldehydes, indicating a prominent role for ring opening. Implications for the oxidation chemistry of cycloalkenes are briefly discussed.
authors.affiliation: Department of Chemistry, University of San Francisco, San Francisco, California 94117, USA. gmeloni@usfca.edu
authors.forename: Giovanni
authors.initials: G
authors.lastname: Meloni
authors.forename: Talitha M
authors.initials: TM
authors.lastname: Selby
authors.forename: David L
authors.initials: DL
authors.lastname: Osborn
authors.forename: Craig A
authors.initials: CA
authors.lastname: Taatjes