Reactions and products revealed by NMR spectra of deuterated dimethylsulfoxide with iodomethane in neutral and basic media

Reactions occurring within each one of two mixtures, a mixture of deuterated dimethylsulfoxide, DMSO-d₆, with CH₃I (system I) and another mixture of DMSO-d₆ with CH₃I, NaOH and water (system II), were monitored by 1D and 2D nuclear magnetic resonance (¹H, ¹³C, heteronuclear multiple quantum correlation, heteronuclear multiple bond correlation and diffusion-ordered NMR spectroscopy). The analysis of the spectra as a function of reaction time revealed the formation of methoxy-bis(trideuteromethyl)sulfonium iodide, 3; the precipitation of hexadeuterated trimethyloxosulfonium, 2a; a methyl exchange between DMSO-d₆ and 2a to produce trideuterated dimethylsulfoxide, DMSO-d₃, 4, and nona-deuterated trimethyloxosulfonium iodide, 2b; and the production of small quantities of methanol, 5, trideuterated dimethylsulfide, 6, and dimethyl ether, 7, in both systems. Only system II precipitated deuterated [Na₄(DMSO-d_x)₁₅][(I₃)₃I], 1a, a green solid with metallic shine that corresponds to an isotopomer of 1, which is produced by the self-assembly of DMSO and CH₃I in the presence of NaOH and water.