Cyclohexoxy and its methyl substituted variants play an important role in atmospheric chemistry. Direct spectral observation of these radicals can provide information about their structures and serve as convenient diagnostics for their monitoring. In this work, we report the first time observation of the LIF spectra of 2-, 3-, and 4-methylcyclohexoxy radicals in supersonic jet-cooled conditions. All spectra are consistent with a single conformer, and thermodynamic analysis of the conformers suggests that the conformer has the diequatorial (e, e) chair structure. Vibrational frequency analysis was performed using CASSCF/6-31+G(d) method on the state of radicals and the vibronic bands were assigned. The origin band of the methyl substituted cyclohexoxy shifted to red with the decrease of the separation distance between the methyl group and the oxygen atom on the ring. Different spectral character of 2-methylcyclohexoxy radical suggested that the neighboring methyl group affected the behavior of the radical on the excited state.
Joshua H. Marks,Xilin Bai,Anatoliy A. Nikolayev,Qi’ang Gong,Cheng Zhu,N. Fabian Kleimeier,Andrew M. Turner,Santosh K. Singh,Jia Wang,Jiuzhong Yang,Yang Pan,Tao Yang,Alexander M. Mebel,Ralf I. Kaiser
Orthocarboxylic acids─organic molecules carrying three hydroxyl groups at the same carbon atom─have been distinguished as vital reactive intermediates by the atmospheric science and physical (organic) chemistry communities as transients in the atmospheric aerosol cycle. Predicted short lifetimes and their tendency to dehydrate to a carboxylic acid, free orthocarboxylic acids, signify one of the most elusive classes of organic reactive intermediates, with even the simplest representative methanetriol (CH(OH)3)─historically known as orthoformic acid─not previously been detected experimentally. Here, we report the first synthesis of the previously elusive methanetriol molecule in low-temperature mixed methanol (CH3OH) and molecular oxygen (O2) ices subjected to energetic irradiation. Supported by electronic structure calculations, methanetriol was identified in the gas phase upon sublimation via isomer-selective photoionization reflectron time-of-flight mass spectrometry combined with isotopic substitution studies and the detection of photoionization fragments. The first synthesis and detection of methanetriol (CH(OH)3) reveals its gas-phase stability as supported by a significant barrier hindering unimolecular decomposition. These findings progress our fundamental understanding of the chemistry and chemical bonding of methanetriol, hydroxyperoxymethane (CH3OOOH), and hydroxyperoxymethanol (CH2(OH)OOH), which are all prototype molecules in the oxidation chemistry of the atmosphere.
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