Oxidation of thiourea and substituted thioureas: a review

The stoichiometry and kinetics of the oxidation of thiourea (SC(NH2)2) by chlorine dioxide (ClO2) have been studied by uv-vis spectrophotometry using conventional and stopped-flow mixing techniques at 250 ± 01°C, pH 03–48 In high acid and initial 10:1 molar ratio of thiourea to chlorine dioxide, thiourea is oxidized relatively rapidly to dithiobisformamidine ion ((NH2)2CSSC(NH2)22+), which slowly decomposes to thiourea, sulfur, and cyanamide (NCNH2) In high acid and excess ClO2, thiourea is oxidized to relatively stable formamidine sulfinic acid ((NH) (NH2)CSO2H) In high acid and molar ratios of ClO2 to thiourea of 5:1 and higher, some oxidation to formamidine sulfonic acid ((NH) (NH2)CSO3H) occurs At lower acidity, along with Cl−, the major ClO2 reduction product, byproduct sulfate is detected and, at pH < 3, ClO2−, also, appears Kinetics data were collected for high excess thiourea with varying pH The [ClO2]-time curves are straight lines with negative slopes that increase in magnitude with increasing [thiourea] The dependence on [thiourea] is first-order; the dependence on [ClO2] is zero-order for 90% of reaction With decreasing pH, the rate increases and the disappearance of ClO2 becomes autocatalytic Studies of the effects of reaction products on the rate of reaction lead to the conclusion that autocatalysis at low pH is due to the greater reactivity of HClO2 compared with ClO2− A 10-step mechanism incorporating a slow one-electron transfer from thiourea to ClO2 to generate the (NH) (NH2)CS · radical and subsequent more rapid reactions has been constructed and implemented in a computer simulation which provides a reasonably accurate fit to the observed kinetics curves © 1993 John Wiley & Sons, Inc

Kinetics and mechanism of the oxidation of thiourea by chlorine dioxide

Mono-, di-, and triprotonation of thiourea (H2N)2CS, was studied by low-temperature 1H, 13C, and 15N NMR spectroscopy in superacidic systems. In FSO3H/SO2ClF at −80 °C, thiourea is monoprotonated e...

Preparation, NMR, Raman, and DFT/IGLO/GIAO-MP2 Study of Mono- and Diprotonated Thiourea and Theoretical Investigation of Triprotonated Thiourea1

The reaction between bromate and 1-methyl-2-thiourea, CH3NH(NH2)CS (MTU), has been studied in acidic medium. The stoichiometry of the reaction in excess MTU has been established as 4BrO3- + 3CH3NH(...

Oxyhalogen-sulfur chemistry : bromate oxidation of 1-methyl-2-thiourea in acidic medium

During the prepn. of AsBr4+[Al(OR)4]-, the novel carbocation CS2Br3+ was synthesized by reaction of AsBr3, Br2, CS2, and Ag[Al(OR)4] (R=C(CF3)3). CS2Br3+ [Al(OR)4]- was characterized by its crystal structure, NMR and IR spectroscopy, and quantum chem. calcns. (including COSMO solvation enthalpies). Addnl. expts. as well as the computed thermodn. indicated two likely reaction pathways: Ag+ + 2Br2 + CS2->CS2Br3+ + AgBr and the direct 4e- oxidn. reaction AsBr4+ + CS2->CS2Br3+ + 1/6As6Br6. Both reactions were obsd. exptl. and are exergonic in soln. by -226 and -56 kJ mol-1 resp. As a result of charge delocalization the C-S and C-Br distances in the cation are shortened by 0.06 to 0.08 .ANG.; the S-Br distances are also slightly shortened indicating a delocalization of the charge also to the bromine atoms in the (S-)Br moieties. Based on an anal. of the cation-anion contacts as well as quantum chem. MP2 calcns., a delocalization model as a planar 10 p electron system is discussed and the p MOs are given. The electronic situation of CS2Br3+ is very close to that in CBr3+, i.e., the properties of SBr moieties and Br atoms as p donors towards a formal C+ center are comparable. [on SciFinder (R)]

Oxidation of CS2 by AsBr4+: The Unexpected Formation of the Simple CS2Br3+ Carbenium Ion

The structure of thiourea nitrate has been determined by three-dimensional X-ray methods. Both Cu Ke and Mo K~ data were obtained with a single-crystal diffractometer and the final R values are 4.9% and 5.5% respectively. The space group is P211m and there are two molecules in the unit cell. All atoms, including hydrogen, lie on mirror planes. The whole structure is built up of layers of atoms, the atoms within each layer being linked by a network of hydrogen bonds.

/pdf/the-crystal-structure-of-thiourea-nitrate-2j4y58r2ng.pdf

W. Song Loong

Papers

The crystal structure of thiourea nitrate