%0 Generic %A Wu, C.-C. %A Jiang, J. C. %A Hahndorf, I. %A Chaudhuri, C. %A Lee, Y. T. %A Chang, H.-C. %D 2000 %T Characterization of Protonated Formamide-Containing Clusters by Infrared Spectroscopy and Ab Initio Calculations:  I. O-Protonation %U https://acs.figshare.com/articles/dataset/Characterization_of_Protonated_Formamide-Containing_Clusters_by_Infrared_Spectroscopy_and_Ab_Initio_Calculations_I_O-Protonation/3721323 %R 10.1021/jp000993n.s007 %2 https://acs.figshare.com/ndownloader/files/5813025 %K vibrational predissociation spectroscopy %K HC %K protonated formamide clusters %K NH 4 %K ab initio calculations %X Characterization of protonated formamide clusters by vibrational predissociation spectroscopy confirms theoretical predictions that O-protonation occurs in preference to N-protonation in formamide. The confirmation is made from a close comparison of the infrared spectra of H+[HC(O)NH2]3 and NH4+[HC(O)NH2]3 produced by a supersonic expansion with the spectra produced by ab initio calculations. For NH4+[HC(O)NH2]3, prominent and well-resolved vibrational features are observed at 3436 and 3554 cm-1. They derive, respectively, from the symmetric and asymmetric NH2 stretching motions of the three formamide molecules linked separately to the NH4+ ion core via three N−H+···O hydrogen bonds. Similarly distinct absorption features are also found for H+[HC(O)NH2]3; moreover, they differ in frequency from the corresponding vibrational modes of NH4+[HC(O)NH2]3 by less than 10 cm-1. The result is consistent with a picture of proton attachment to the oxygen atom, rather than the nitrogen atom in H+[HC(O)NH2]3. We provide in this work both spectroscopic and computational evidence for the O-protonation of formamide and its clusters in the gas phase. %I ACS Publications