Eine unerwartet stabile Sulfensäure: 4,6-Dimethoxy-1,3,5-triazin-2-sulfensäure; Synthese, Eigenschaften, Molekül- und Kristallstruktur / Unexpectedly Stable Sulfenic Acid: 4,6-Dimethoxy-1,3,5-triazine-2-sulfenic Acid; Synthesis, Properties, Molecular and Crystal Structure

Abstract

4,6-Dimethoxy-1,3,5-triazine-2-sulfenic acid (1) was prepared by the reaction of 4,6-dimethoxy-1,3,5-triazine-2(1H)-thion (3) with 2-benzenesulfonyl-3-(p-nitrophenyl)-oxaziridine (2) in THF solution and isolated as a stable crystalline solid. The new compound was characterized by analytical and spectroscopic data (IR, 1H and 13C NMR, UV, MS) supported by MNDO-PM 3 calculations. UV spectrometry was used for exact determination of the ionization constant of 1(pKa = 5.86 ± 0.02 at 20°C). According to 13C NMR data and X-ray analysis the sulfenic acid 1 adopts the sulfenyl structure (R—SOH) in the condensed phase. Crystal data of 1 (90 K): a = 8.418(3), b = 21.289(6), c = 4.411(1) Å, Z = 4, P 21212, R = 0.0304, Rw = 0.0354 for 4105 unique reflections and 122 parameters. In the crystal, the molecules form dimers by two strong intermolecular O—H ••• N hydrogen bonds. The 6-membered ring shows alternating C—N bond lengths and is almost planar. The experimental electron deformation density (EDD) decreases in the order C—N > C—O ≈ C—S > S—O and is described in detail for the vicinity of the S atom.