STRUCTURAL DETERMINATION OF [C7H7O]+ IONS IN THE GAS-PHASE BY ION-CYCLOTRON RESONANCE SPECTROMETRY
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The [C7H7O]+ ions from a series of compounds have been studied using ion cyclotron resonance spectrometry. The techniques employed in this gas phase ion structure determination of [C7H7O]+ were photodissociation, ionmolecule reactions, and collisionally activated dissociation using a Fourier transform mass spectrometer (FTMSCAD). In addition to the low energy FTMSCAD results, high energy CAD data obtained with a sector mass spectrometer is also provided. Evidence was found for five unique [C7H7O]+ structures, including the hydroxybenzyl ion, the hydroxytropylium ion, the protonated benzaldehyde ion, the methylaryloxy ion and the phenyl methylene ether ion. Ionmolecule reactions, invovling both proton transfer and methylene transfer, provided the most unambiguous results and yielded qualitative and quantitative evidence for the five structures. However, a combined approach using the three techniques was necessary to identify all of the structures. The tropylium form of [C7H7O]+ was found to absorb strongly at 305 nm, while the protonated benzaldehyde ion was found to have a strong absorption band at 305 nm and a weak band at 370 nm. The proton affinity of 2,4,6cycloheptatrienone was determined to be 9188 kJ mol1, which is considerably lower than a previously reported value. In addition, deprotonation reactions of the methylaryloxy ion yielded a proton affinity of 87114 kJ mol1 for 4methylenecyclohexa2,6diene1one. Copyright 1983 Wiley Heyden Ltd.
