UNEXPECTEDLY STABLE SULFENIC ACID - 4,6-D IMETHOXY-1,3,5-TRIAZINE-2-SULFENIC ACID - SYNTHESIS, PROPERTIES, MOLECULAR AND CRYSTAL-STRUCTURE

4,6-Dimethoxy-1,3,5-triazine-2-sulfenic acid (1) was prepared by the r eaction of 4,6-dimethoxy-1,3,5-triazine-2(1H)-thion (3) with 2-benzene sulfonyl-3-(p-nitrophenyl)-oxaziridine (2) in THF solution and isolate d as a stable crystalline solid. The new compound was characterized by analytical and spectroscopic data (IR, H-1 and C-13 NMR, UV, MS) supp orted by MNDO-PM 3 calculations. UV spectrometry was used for exact de termination of the ionization constant of 1 (pK(a) = 5.86 +/- 0.02 at 20-degrees-C). According to C-13 NMR data and X-ray analysis the sulfe nic acid 1 adopts the sulfenyl structure (R - SOH) in the condensed ph ase. Crystal data of 1 (90 K): a = 8.418(3), b = 21.289(6), c = 4.411( 1) angstrom, Z = 4, P 2(1)2(1)2, R = 0.0304, R(w) = 0.0354 for 4105 un ique reflections and 122 parameters. In the crystal, the molecules for m dimers by two strong intermolecular O - H ... N hydrogen bonds. The 6-membered ring shows alternating C-N bond lengths and is almost plana r. The experimental electron deformation density (EDD) decreases in th e order C-N > C-O almost-equal-to C-S > S-O and is described in detail for the vicinity of the S atom.