Role of Hydrogen Bonding on the Reactivity of Thiyl Radicals: A Mass Spectrometric and Computational Study Using the Distonic Radical Ion Approach

Sandra Osburn; Bun Chan; Victor Ryzhov; Leo Radom; Richard A J O'Hair

doi:10.1021/acs.jpca.6b08544

Role of Hydrogen Bonding on the Reactivity of Thiyl Radicals: A Mass Spectrometric and Computational Study Using the Distonic Radical Ion Approach

J Phys Chem A. 2016 Oct 20;120(41):8184-8189. doi: 10.1021/acs.jpca.6b08544. Epub 2016 Oct 11.

Authors

Sandra Osburn¹, Bun Chan², Victor Ryzhov³, Leo Radom⁴, Richard A J O'Hair¹

Affiliations

¹ School of Chemistry and Bio21 Molecular Science and Biotechnology Institute, University of Melbourne , 30 Flemington Rd, Parkville, Victoria 3010, Australia.
² Graduate School of Engineering, Nagasaki University , Bunkyo 1-14, Nagasaki 852-8521, Japan.
³ Department of Chemistry and Biochemistry and Center for Biochemical and Biophysical studies, Northern Illinois University , Dekalb, Illinois 60115, United States.
⁴ School of Chemistry, University of Sydney , Sydney, NSW 2006, Australia.

PMID: 27726360
DOI: 10.1021/acs.jpca.6b08544

Abstract

Experimental and computational quantum chemistry investigations of the gas-phase ion-molecule reactions between the distonic ions ⁺H₃N(CH₂)_nS^• (n = 2-4) and the reagents dimethyl disulfide, allyl bromide, and allyl iodide demonstrate that intramolecular hydrogen bonding can modulate the reactivity of thiyl radicals. Thus, the 3-ammonium-1-propanethiyl radical (n = 3) exhibits the lowest reactivity of these distonic ions toward all substrates. Theoretical calculations on this distonic ion highlight that its most stable conformation involves a six-membered ring configuration, and that it has the strongest intramolecular hydrogen bond. In addition, the calculations indicate that the barrier heights for radical abstraction by this hydrogen-bond-stabilized 3-ammonium-1-propanethiyl radical are the highest among the systems examined, consistent with the experimental observations.