10.1021/jp000993n.s017
C.-C. Wu
C.-C.
Wu
J. C. Jiang
J. C.
Jiang
I. Hahndorf
I.
Hahndorf
C. Chaudhuri
C.
Chaudhuri
Y. T. Lee
Y. T.
Lee
H.-C. Chang
H.-C.
Chang
Characterization of Protonated Formamide-Containing Clusters by Infrared Spectroscopy
and Ab Initio Calculations: I. O-Protonation
American Chemical Society
2000
vibrational predissociation spectroscopy
HC
protonated formamide clusters
NH 4
ab initio calculations
2000-09-30 00:00:00
Dataset
https://acs.figshare.com/articles/dataset/Characterization_of_Protonated_Formamide-Containing_Clusters_by_Infrared_Spectroscopy_and_Ab_Initio_Calculations_I_O-Protonation/3721326
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<sup>+</sup>[HC(O)NH<sub>2</sub>]<sub>3</sub> and NH<sub>4</sub><sup>+</sup>[HC(O)NH<sub>2</sub>]<sub>3</sub> produced
by a supersonic expansion with the spectra produced by ab initio calculations. For NH<sub>4</sub><sup>+</sup>[HC(O)NH<sub>2</sub>]<sub>3</sub>,
prominent and well-resolved vibrational features are observed at 3436 and 3554 cm<sup>-1</sup>. They derive, respectively,
from the symmetric and asymmetric NH<sub>2</sub> stretching motions of the three formamide molecules linked separately
to the NH<sub>4</sub><sup>+</sup> ion core via three N−H<sup>+</sup>···O hydrogen bonds. Similarly distinct absorption features are also
found for H<sup>+</sup>[HC(O)NH<sub>2</sub>]<sub>3</sub>; moreover, they differ in frequency from the corresponding vibrational modes of
NH<sub>4</sub><sup>+</sup>[HC(O)NH<sub>2</sub>]<sub>3</sub> by less than 10 cm<sup>-1</sup>. The result is consistent with a picture of proton attachment to the
oxygen atom, rather than the nitrogen atom in H<sup>+</sup>[HC(O)NH<sub>2</sub>]<sub>3</sub>. We provide in this work both spectroscopic
and computational evidence for the O-protonation of formamide and its clusters in the gas phase.