Iodination of Acetic Anhydride
Abstract Generated abstract
This paper reports a method for preparing iodoacetic acid by direct iodination of acetic anhydride, a reaction the authors state had not previously been described. The procedure uses iodine in the presence of concentrated sulfuric acid and nitric acid, followed by hydrolysis and extraction, and is proposed to proceed through formation of diiodoacetic anhydride. The method gives iodoacetic acid in 70 to 75 percent yield with a melting point of 82 to 83°C, and is presented as advantageous over earlier routes from chloroacetic acid because of higher yield and less expensive starting materials.
Full Text
Iodination of Acetic Anhydride
A. N. Novikov, P. I. Siyanko
(Presented by the scientific seminar of the departments and laboratories of organic synthesis)
The reaction of iodination of acetic anhydride has not been described in the literature. We have shown for the first time that iodine reacts with acetic anhydride in the presence of a nitrating mixture. As a result, iodoacetic acid is formed in good yield. Apparently, diiodoacetic anhydride is first formed, which is then hydrolyzed to iodoacetic acid. Under analogous conditions, glacial acetic acid is not iodinated.
Iodoacetic acid can be used as a strong murine poison, a plant-growth inhibitor, a contact insecticide against insects resistant to DDT, and a defoliant for cotton, beans, and potatoes [1]. It is an inhibitor of certain enzymes and is therefore used in biochemical studies, as well as for the quantitative determination of sulfur-containing amino acids in proteins [2].
Known methods for obtaining iodoacetic acid are based on the classical aliphatic-series reaction of substituting chlorine in chloroacetic acid with iodine [3, 4, 5]. The yield of iodoacetic acid based on sodium iodide is 30–60%. It has been proposed to obtain iodoacetic acid by high-temperature iodination (800°C) of acetic acid [6]. The product yield is not given. According to a U.S. patent, iodoacetic acid with a melting point of 74–79°C (reference value 82–83°C) is prepared (yield not indicated) from ketene and iodine chloride [7].
The new method developed by us for obtaining iodoacetic acid has advantages over the known ones: a higher yield of iodoacetic acid (70–75%) and cheaper starting materials.
Experimental Part
To a mixture of 54 g of acetic anhydride, 25.4 g of finely ground iodine, and 10 ml of concentrated sulfuric acid at a temperature of 50–60°C in a heated bath and with vigorous stirring, 1.5 ml of nitric acid, d 1.4, is added dropwise over 1.5 hours. The heating and stirring are then continued for another 30–40 minutes. After the iodine precipitate has disappeared (the solution acquires a brown color), the reaction mixture is cooled, diluted with 15 ml of water, and at a temperature of 45–55°C water, nitric acid, and acetic acid are distilled off under vacuum. From the residue in the flask, the iodoacetic acid is extracted with boiling petro-
petroleum ether. After the solution is cooled, the precipitated iodoacetic acid is filtered off, washed with cold petroleum ether, and dried. The yield of iodoacetic acid is 75%; melting point 82–83°C.
A mixed sample with iodoacetic acid obtained from chloroacetic acid and sodium iodide showed no depression of the melting point.
Conclusions
A new method has been developed for obtaining iodoacetic acid, based on the direct iodination of acetic anhydride in the presence of a sulfur–nitrogen mixture.
References
- U.S. Patent 2820057, 1958; RZhKhim., ref. 79427P, 1959.
- Brief Chemical Encyclopedia, Moscow, Soviet Encyclopedia, vol. 2, p. 294, 1963.
- I. Guben, Methods of Organic Chemistry, Moscow, ONTI-NKTP, vol. 3, issue 3, p. 447, 1935.
- R. A. Durie. J. Chem. Soc., p. 1181, 1950.
- Japanese Patent 4322, 1957; RZhKhim., ref. 48799P, 1960.
- U.S. Patent 2833822, 1958; RZhKhim., 10J94P, 1961.
- U.S. Patent 2820057, 1958; RZhKhim., ref. 48799P, 1960.