The Formation and Characterization of Three-Membered Ring Carbanions in the Gas Phase:  An Experimental and Theoretical Investigation of the Conjugate Bases of Thiirane, ThiiraneS-Oxide, and ThiiraneS,S-Dioxide

Abstract

Deprotonation of thiirane, thiirane S-oxide, and thiirane S,S-dioxide was carried out in the gas phase, and the resulting anions were studied through a series of ion-molecule reactions. The cyclic conjugate bases of thiirane (1b) and thiirane S,S-dioxide (3a) are formed whereas a facile ring opening isomerization to vinyl sulfenate anion (2d, CH 2 dCHSO -) is observed in the thiirane S-oxide case. Vinyl thiolate, the rearrangement product of the conjugate base of thiirane, also is obtained. Proton affinities were determined for 1b, 2d, and 3a. High-level ab initio calculations were also carried out, and the results compared with those obtained from experiment. Orbital arguments are advanced to explain the relative barriers to ring opening for the three anions of interest.

Synthesis and Properties of the Strained Alkene Perfluorobicyclo[2.2.0]hex-1(4)-ene

“…Other gas phase experiments were conducted by S.R.K. with a dual cell Fourier transform mass spectrometer that was described previously . Low-energy electron ionization (1.6 eV) or the reduction of 1 by NO – (which was generated from nitrous oxide) was used to produce 1a .…”

“…with a cell Fourier transform mass spectrometer that was described previously. 27 Low-energy electron ionization (1.6 eV) or the reduction of 1 by NO − (which was generated from nitrous oxide) was used to produce 1a. This ion was isolated and then transferred to the second reaction region in the instrument where it was cooled with a pulse of argon, reisolated, and allowed to react with selected reference reagents.…”

A Computational Determination of the Origins of Diastereoselective Alkylations of a Cysteinesulfenate Anion

“…The presence of the lithium reduces the bond angle a few degrees in the various forms of 1•Li (#1-4 vs. #5-10) and 2•Li (#11-14 vs. # [15][16][17][18][19][20]. By analogy, the <CSO reduces when going from counterion-free sulfenate (21)(22)(23)(24)(25)(26)30) to sulfenic acid (#27-29, 31). While employing a variety of gas phase computational methods, Perkins and coworkers [2b] determined the relative gas phase energies of methanesulfenate while varying its <CSO over a wide range.…”

“…# [a] Compound State Bond length Angle Comment [d] r(S-O) [b] C-S-O [c] 1 [24] hindered [e] ArSO -[f ] solid 1.558(6) 107.4(3) K + proximal [g] 22 ref [24] hindered [e] ArSO -[f ] solid 1.485(5) 110.0(3) K + sequestered [h] 23 ref [25] hindered [e] ArCH 2 SO -[f ] solid -106.6(8) K + sequestered, r(K-O) 2.7559(13) [h] 24 ref [26] s-cis-ethenyl sulfenate gas [i] 1.587 107.5 no counterion 25 ref [26] s-trans-ethenyl sulfenate gas [i] 1.602 106.5 no counterion 26 ref[8b] PhSO -CPME [j] 1.547 109.4 no counterion 27 ref [27] hindered [e] ArSOH [f ] solid 1.679(5) 100.3(3) sulfenic acid 28 ref [28] hindered [e] ArCH 2 SOH [f ] solid 1.631(4) 100.96 (18) sulfenic acid 29 ref [29] thiophenetriptycene-8-SOH [f ] solid 1.622(9) 102.3(5) sulfenic acid 30 ref [20] CH 3 SOgas [k] 1.597 102.9 no counterion 31 ref [20] CH 3 SOH gas [k] 1. 2.…”

10 Gas phase organic ion–molecule reaction chemistry

“…that were generated from various heterocyclic precursors. 96 Kass and co-workers 97 reported the reactivity and thermochemistry of ionic species formed from thiirane derivatives (i.e., thiirane, thiirane S-oxide, and thiirane S,S-dioxide). When these heterocycles are treated with bases, MÀ1 ions are formed, but in some cases they undergo ring opening.…”