Theoretical investigation of intramolecular π-type hydrogen bonding and internal rotation of 2-cyclopropen-1-ol, 2-cyclopropen-1-thiol and 2-cyclopropen-1-amine

ABSTRACT

Theoretical computations utilising both CCSD and MP2 methods and the cc-pVTZ basis set have been carried out to determine the structures of several conformations as well as the internal rotation potential energy functions for 2-cyclopropen-1-ol, 2-cyclopropen-1-thiol and 2-cyclopropen-1-amine. The energies and wavefunctions for these potential functions have also been computed. Each of these molecules has an energy minimum corresponding to a conformation with intramolecular π-type hydrogen bonding. The π bonding stabilisation is about 2.3 kcal/mole for the alcohol, 2.1 kcal/mole for the thiol, and about 2.5 kcal/mole for the amine. The results for the thiol demonstrate a rare example of intramolecular π-type hydrogen bonding. The calculated O–H, S–H, N–H, and C=C stretching frequencies have also been compared for the conformations with and without the π-type hydrogen bonding. The C=C stretching frequency is substantially lower in all cases for the hydrogen bonded conformers.

GRAPHICAL ABSTRACT

KEYWORDS:

• π-type hydrogen bonding
• internal rotation
• 2-cyclopropen-1-ol
• 2-cyclopropen-1-thiol
• 2-cyclopropen1-amine

Acknowledgments

This paper is dedicated to the memory of Dieter Cremer who made many outstanding contributions, particularly to theoretical studies of cyclic molecules, that greatly increased our understanding of their conformations. The authors wish to thank the Robert A. Welch Foundation (grant A-0396) for financial support. Computations were carried out on the Texas A&M University Department of Chemistry computer system funded by the National Science Foundation, grant number CHE-0541587. The Laboratory for Molecular Simulation provided the Semichem AMPAC/AGUI software.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Esther J. Ocola http://orcid.org/0000-0002-2845-283X

Jaan Laane http://orcid.org/0000-0003-4423-6122

Additional information

Funding

The authors wish to thank the Robert A. Welch Foundation [grant number A-0396] for financial support. Computations were carried out on the Texas A&M University Department of Chemistry computer system funded by the National Science Foundation [grant number CHE-0541587]. The Laboratory for Molecular Simulation provided the Semichem AMPAC/AGUI software.