Detailed mechanistic studies into the reactivities of thiourea and substituted thiourea oxoacids: decompositions and hydrolyses of dioxides in basic media.

Dioxides of methylthiourea (methylaminoiminomethanesulfinic acid, MAIMSA) and dimethylthiourea (dimethylaminoiminomethanesulfinic acid, DMAIMSA) were synthesized and, together with thiourea dioxide (aminoiminomethanesulfinic acid, AIMSA), were studied with respect to their decompositions and hydrolyses in basic aqueous media. All three were stable in acidic media and existed as zwitterions with the positive charge spread out on the 4-electron 3-center N-C-N skeleton and the negative charge delocalized over the two oxygen atoms. All three are characterized by long and weak C-S bonds that are easily cleaved in polar solvents through a nucleophilic attack on the positively disposed carbon center, followed by cleavage of the C-S bond.