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In organic chemistry, isothiouronium is a functional group with the formula [RSC(NH2)2]+ (R = alkyl, aryl) and is the acid salt of isothiourea. The H centres can also be replaced by alkyl and aryl. Structurally, these cations resemble guanidinium cations. The CN2S core is planar and the C-N bonds are short.
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Synthesis
Salts comprising these anions are typically prepared by alkylation of thiourea:
SC(NH2)2 + RX → [RSC(NH2)2]+X−Reactions
Hydrolysis of isothiouronium salts gives thiols.
[RSC(NH2)2]+X− + NaOH → RSH + OC(NH2)2 + NaXIsothiouronium salts in which the sulfur has been alkylated, such as S-methylisothiourea hemisulfate (CAS No: 867-44-7), will convert amines into guanidinium groups. This approach is sometimes called the Rathke synthesis after Bernhard Rathke who first reported it in 1881.
RNH2 + [MeSC(NH2)2]+X− → RNC(NH2)2]+X− + MeSHChelating resins with isothiouronium groups are used to recover mercury and noble metals including platinum from solutions.