Effect of Bond Multiplicity upon Hydrogen Bonding and Proton Transfers. Double Bonded Atoms

Authors

Steve Scheiner, Utah State UniversityFollow
Lan Wang

Document Type

Article

Journal/Book Title

Journal of the American Chemical Society

Publication Date

5-1992

Publisher

American Chemical Society

Volume

114

Abstract

Ab initio methods are used to study the interactions between H₂C=CH₂ and H₂C=NH and their deprotonated anions. (H₂CCH-H^_...CHCH₂)^- is the most weakly bound with a complexation energy of 5.6 kcal/mol at the correlated MP2 level as compared to the stronger interaction of 10.3 for (HNCH-H^_...CHNH)^- where the peripheral C atom has been replaced by N. The strongest interaction of 15.4 kcal/mol is observed in (H₂CN-H^_...NCH₂)^- where N atoms participate directly in the H-bond. (H₂CCH-H^_...CHCH₂)^- contains the longest intermolecular separation while the N-N distance in the latter complex is the shortest. This separation between subunits undergoes a contraction between 0.5 and 0.9 Å as the proton reaches the transfer midpoint. The highest proton transfer barrier of 13 kcal/mol is observed for (H₂CCH-H^_...CHCH₂)^-. In contrast, the small barrier in (H₂CN-H^_...NCH₂)^- is eliminated altogether when zero-point vibrations are considered. Transfer rates are computed using modified RRKM theory. These results are placed within the broader context of other complexes in which the atoms participating in the H-bond are single- and triple-bonded within their respective subunits so as to arrive at systematic conclusions regarding the effects of such multiple bonding upon the energetics of H-bond formation and proton transfer.

Comments

Originally published in the Journal of the American Chemical Society by the American Chemical Society . Publisher’s PDF available through remote link. DOI: 10.1021/ja00036a012

Recommended Citation

Effect of Bond Multiplicity upon Hydrogen Bonding and Proton Transfers. Double Bonded Atoms S. Scheiner, L. Wang J. Am. Chem. Soc. 1992 114 (10), 3650-3655.