Negative ion photoelectron measurements have been carried out for the anionic products of the reaction of OH�  with ortho, meta and para methylphenols in a flowing afterglow ion source. The photoelectron spectra of the three methylphenoxide anions allow direct measurement of the electron affinities of the corresponding methylphenoxyl radicals. The photoelectron spectra of the anions are successifully reproduced by a Franck-Condon simulation based on the optimized geometries and the normal vibrational modes obtained from  DFT electronic structure calculations at the B3LYP/6-311++G(2d,2p) level. Using the measured  electron affinities together with the known O�H bond dissociation energies of the ortho, meta and paramethylphenols ((D0 (CH3PhO�H)), a negative ion thermochemical cycle is utilized to obtain the deprotonation enthalphy(?acidH298K (CH3PhO�H)) of the three methyl-substituted phenol isomers. While OH�  is sufficiently basic to deprotonate the CH3 groups in all the three methylphenols, methyl deprotonation is only observed for m-methylphenol.Supported by NSF Grants CHE1213862, PHY1125844  and AFOSR (WCL) Grant FA9550-12-1-0125

Ultraviolet photoelectron spectroscopy of methylphenoxide anions

248th National Meeting (2014)

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