Unraveling structure-reactivity relationships in SNV reactions: kinetics of the reactions of methoxybenzylidenemalononitrile, 2-(methylthiobenzylidene)-1,3-indandione, 2-(benzylthiobenzylidene)-1,3-indandione, and methyl beta-methylthio-alpha-nitrocinnamate with OH- and thiolate ions in aqueous DMSO.