INTERACTION OF THIOUREA DIOXIDE WITH n-BUTYLAMINE

The influence of n-butylamine on the stability and reducing activity of thiourea dioxide (TDO, aminoiminomethanesulfinic acid, formamidinesulfinic acid) in the reaction with azo dye Orange II has been studied. The addition of an excess of n-butylamine leads to the increase in reducing activity of thiourea dioxide in the reaction with the azo dye Orange II in strongly alkaline solutions, whereas the stability of thiourea dioxide decreases under these conditions. It has been shown that with an excess of n-butylamine, N,N'-di-n-butylthiourea dioxide is formed. N-n-butylthiourea dioxide was synthesized and isolated in the solid state as a product of the reaction of thiourea dioxide with n-butylamine in an acidic medium (pH 5) at a molar ratio of reagents 1:1. This compound was characterized by IR, 1Н and 13С NMR spectroscopy. N-n-butylthiourea dioxide has a higher solubility in water than the thiourea dioxide, but lower reducing activity in the reaction with azo dye Orange II in the range of pH 6.9–11.8. The formation of active reducing agent sulfoxylate in course of TDO decomposition leads to its high reducing activity in alkaline aqueous solutions. It has been shown that the rates of decomposition of the studied compounds increase with increasing pH. It has been established that N-n-butylthiourea dioxide is more stable in alkaline media than thiourea dioxide. Based on the previous data and data obtained in this work the following sequence of reducing activity of thioureas dioxides in strongly alkaline media was proposed: N,N'-dialkylthiourea dioxides > thiourea dioxide > N-alkylthiourea dioxides. The stability of thiourea dioxides in strongly alkaline aqueous solutions increases in reverse order.