Reaction of Thiourea with Hydrogen Peroxide: 13 C NMR Studies of an Oxidative/Reductive Bleaching Process

Abstract

Thiourea's reaction with hydrogen peroxide in solution under bleaching conditions at three different pH values has been investigated using ¹³C NMR spectroscopy. Since this reaction is fast and exothermic, it is essential that short total acquisition times be used to accumulate sufficient data to detect different species formed during the reaction. As the abundance of ¹³C in the reactants in the concentration range studied is very low, ¹³C-labeled thiourea was used as the starting material. Sufficient data were accumulated in short acquisition times (2–4 minutes) to identify different species formed during the reaction. The results showed that different intermediate products are formed during the reactions, depending on the pH of the medium and the molar ratio of the reactants. The reaction goes through a thiourea dioxide intermediate; this then hydrolyzes under heat and neutral or alkaline conditions to yield sulfonate anion and urea if the initial reaction of thiourea with hydrogen peroxide is allowed to take place in acidic/neutral medium (pH = 4.0–7.0). Because thiourea dioxide hydrolyzes in solution, there is a rapid change in redox potential from a positive value to a high negative value. The species causing the negative redox potential, and hence the species responsible for reductive bleaching, is believed to be the sulfinate anion. The reaction of thiourea with hydrogen peroxide in hydrochloric acid at pH < 1 results in the formation of formamidine disulfide dihydrochloride, which decomposes at pH values greater than 1.

Get full access to this article

View all access options for this article.

References

Arifoglu

Marmer

W. N.

Carr

C. M.

, Sequential Oxidative and Reductive Bleaching of Wool in a Single Bath, Textile Res. J. 60, 319–328 (1990).

Arifoglu

Marmer

W. N.

, Sequential Oxidative and Reductive Bleaching of Stained and Pigmented Wool in a Single Bath, Textile Res. J. 60, 549–554 (1990).

Arifoglu

Marmer

W. N.

, Sequential Oxidative and Reductive Bleaching in a Multicomponent Single Liquor System, U.S. patent 4,961,752, October 9, 1990, and subsequent Continuations-in-Part and Divisional Cases.

de Barnett

E. B.

, The Action of Hydrogen Dioxide on Thiocarbamides, J. Chem. Soc. 97, 63–65 (1910).

Boeseken

, Oxidation Products of Thiourea, The Dioxide as a Derivative of Sulfoxylic Acid (H2SO2), Proc. Acad. Sci. Amsterdam 39, 717–721 (1936).

Buechler

Mittermeier

Pollwein

, Continuous Production of Thiourea Dioxide from Thiourea and Hydrogen Peroxide, German patent 2,736,943, March, 8, 1979; Chem. Abstr. 90, 168098v.

Cegarra

Gacén

Caro

Pepio

, Wool Bleaching with Thiourea Dioxide, J. Soc. Dyers Colour. 104, 273–279 (1988).

Duffield

P. A.

, Review of Wool Bleaching, IWS Technical Information Bulletin, 1986.

Fujimoto

Watanabe

Kushibe

, Thiourea Dioxide, Jpn. Kokai Tokyo Koho 80, 17, 339 (1980); Chem. Abstr. 93, 149830y.

10.

Gattow

Manz

, Oxidation Products of Thiourea, Z. Anorg. Allg. Chem. 561, 66–72 (1988).

11.

Golovnya

V. A.

Bolotova

G. T.

, Reduction Properties of Thiourea Dioxide and of its Decomposition Products, Zhur. Neorg. Khim. 6, 2254–2262 (1961); Chem. Abstr. 56, 9696a.

12.

Grigorova

Wright

S. A.

, Simultaneous Determination of Thiourea and Formamidine Disulfide, Using Reversed-Phase High-Performance Liquid Chromatography and a UV Detector, J. Chromatog. 368, 444–449 (1986).

13.

Hector

D. S.

, Einwirkung von Oxydationsmitteln auf aliphatische Thioharnstoffe, J. Prakt. Chem. 44, 492–506 (1891).

14.

Hoffmann

Edwards

J. O.

, Kinetics and Mechanism of the Oxidation of Thiourea and N, N'-Dialkyl-thioureas by Hydrogen Peroxide, Inorg. Chem. 16 (12), 3333–3338 (1977).

15.

Kelner

M. J.

Bagnell

Kenneth

J. W.

, Thioureas React with Superoxide Radicals to Yield a Sulfhydryl Compound, J. Biol. Chem. 265, 1306–1311 (1990).

16.

Kruglov

A. I.

Thiourea dioxide, U.S.S.R. patent 1,133,269, January 7, 1985; Chem. Abstr. 102, 22047 1u.

17.

Lastovskii

R. P.

Globus

R. L.

Yarovenko

E. Ya.

, Reaction Mechanism of Formamidinesulfonic Acid Formation by Oxidation of Thiourea with Hydrogen Peroxide, Zh. Org Khim. 3 (6), 1002–1005 (1967); Chem. Abstr. 67, 116354f.

18.

Marshall

, The Dissociation of the Compound of Iodine and Thiourea, Proc. R. Soc. Edinburgh 24, 233–237 (1902).

19.

Preisler

P. W.

Berger

, Oxidation-Reduction Potentials of Thio-Dithio Systems: Thiourea-Formamidine Disulfide, J. Am. Chem. Soc. 69, 322–325 (1947).

20.

Randall

L. O.

, Reaction of Thiol Compounds with Peroxidase and Hydrogen Peroxide, J. Biol. Chem. 164, 521–527 (1946).

21.

Storch

, The Action of Hydrogen Dioxide on Thio-carbamides, Monatsh. Chem. 11, 452 (1890).

22.

Streit

Reincke

Vescia

, Single Bath Oxidative and Reductive Bleaching of Wool—Using a Sul-phinic Acid Derivative as Reductive Bleaching Agent during Heating-up and Hydrogen Peroxide as Oxidative Bleaching Agent, German patent 3,433,926 A1, March 27, 1986; Chem. Abstr. 105, P80609e.

23.

“Thiols,” in “Encyclopedia of Chemical Technology,” 3rd ed., Kirk-Othmer, vol. 22, Wiley-Interscience Publication, New York, 1983, pp. 946–964.

24.

“Thiourea,” ch. 1 in “Organic Chemistry of Bivalent Sulfur,” vol. V, E. E. Reid, Chemical Publishing Co., Inc., New York, 1963.

25.

Walter

J. L.

Ryan

J. A.

Lane

T. J.

, A Study of Thiourea and Substituted Thiourea Analogs by the Bjerrum Titration Method, J. Am. Chem. Soc. 78, 5560–5562 (1956).

26.

Weiss

, Thiourea Dioxide: A Safe Alternative to Hydrosulfite Reduction, Am. Dyest. Rep. 67 (8), 35–38 and (9), 72–74 (1978).