Ammonium thiocyanate, conversion

According to an O.S. amendment sheet, the procedure as described [1] is dangerous because the reaction mixture (dicyanodiamide and ammonium nitrate) is similar in composition to commercial blasting explosives. This probably also applies to similar earlier preparations [2]. An earlier procedure which involved heating ammonium thiocyanate, lead nitrate and ammonia demolished a 50 bar autoclave [3], TGA and DTA studies show that air is not involved in the thermal decomposition [4], Explosive properties of the nitrate are detailed [5], An improved process involves catalytic conversion at 90-200°C of a molten mixture of urea and ammonium nitrate to give 92% conversion (on urea) of guanidinium nitrate, recovered by crystallisation. Hazards of alternative processes are listed [6],... 

Several methods have been introduced which express the degree of oxidation deterioration in terms of hydroperoxides per unit weight of fat. The modified Stamm method (Hamm et at 1965), the most sensitive of the peroxide determinations, is based on the reaction of oxidized fat and 1,5-diphenyl-carbohydrazide to yield a red color. The Lea method (American Oil Chemists Society 1971) depends on the liberation of iodine from potassium iodide, wherein the amount of iodine liberated by the hydroperoxides is used as the measure of the extent of oxidative deterioration. The colorimetric ferric thiocyanate procedure adapted to dairy products by Loftus Hills and Thiel (1946), with modifications by various workers (Pont 1955 Stine et at 1954), involves conversion of the ferrous ion to the ferric state in the presence of ammonium thiocyanate, presumably by the hydroperoxides present, to yield the red pigment ferric thiocyanate. Newstead and Headifen (1981), who reexamined this method, recommend that the extraction of the fat from whole milk powder be carried out in complete darkness to avoid elevated peroxide values. Hamm and Hammond (1967) have shown that the results of these three methods can be interrelated by the use of the proper correction factors. However, those methods based on the direct or indirect determination of hydroperoxides which do not consider previous dismutations of these primary reaction products are not necessarily indicative of the extent of the reaction, nor do they correlate well with the degree of off-flavors in the product (Kliman et at. 1962). 

Thiourea is tbimed by heating ammonium thiocyanate at 170°C. After about an hour, 25% conversion is achieved. With HQ, thiourea forms thiourea hydrochloride with mercuric oxide, thiourea forms a salt and with silver chloride, it forms a complex salt. 

The dependence of the rate constant on temperature for the conversion of thiourea to ammonium thiocyanate in aqueous solution is given in Table 3.6. 

Conversion of thiourea to ammonium thiocyanate - determination of activation energy from experimental data, 93-95... 

HCN is not completely stable and is marketed as a stabilized (often with H3PO4), flammable, anhydrous material. It reacts when heated, or in the presence of base or water, and may polymerize violently in contact with strong acids (e.g., sulfuric acid). Polymerization, once initiated, can be autocatalytic and, under confined conditions, lead to an explosion. It can be removed from waste streams by conversion to ammonium thiocyanate, a process involving scmbbing the waste stream with elemental sulfur in water (http //www.chemalliance.org). 

The treatment of styrenes with ammonium thiocyanate and CAN in MeCN results in the formation of dithiocyanates. Under an oxygen atmosphere, phenacyl thiocyanates can be the major products. The thiocyanation of indoles also proceeds under similar conditions. Chemoselective thioacetalization of aldehydes and the conversion of epoxides to their corresponding thiiranes can be operated under mild conditions with the catalysis of CAN. As an extension, selenocyanation can be conducted in a similar fashion with CAN/KSeCN. ... 

Barium thiocyanate was first prepared by Berzelius, who roasted barium hexacyanoferrate(II) with sulfur. It has also been obtained by reaction of barium carbonate with a solution of thiocyanic acid, by conversion of ammonium thiocyanate through the copper (I) thiocyanate by consecutive reactions with copper(I) chloride and barium hydroxide, by treatment of Prussian blue with barium sulfide, and by reaction of barium sulfide, sulfur, and cyanamide. The procedure described below makes possible the preparation of barium thiocyanate in any desired quantity from barium hydroxide and ammonium thiocyanate as starting materials. The 3-hydrate, " which is obtained first, is dehydrated readily to yield anhydrous barium thiocyanate. 

Using Bi(0Tf)3 in catalytic amounts, the efficient conversion of epoxides to thi-iranes with ammonium thiocyanate or thiourea has been reported. It is noteworthy that the reaction works with thiourea, the compound being a less reactive source of sulfur (Equation 43) [86c]. 

Differential conductometric titration has been used [674, 675] for the determination of chlorine in some chloroorganosilane mixtures. The method is based on the quantitative conversion of the chlorosilanes into the alkylthiocyanato derivatives by the action of ammonium thiocyanate, followed by conductometric titration in methyl cyanide/ethyl ether (2/3) solvent with 0.1 N amidopyrine in benzene. The monosub-... 

Figure 10. Scanning electron micrograph of a cross-section (top) of a diquaternary ammonium cellulose prepared by reaction of a DEAE cellulose (2.57% N) with dllodopentane and exchanged to thiocyanate form (100% conversion) and EDAX (bottom) showing distribution of s throughout fiber.

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