Ammonium thiocyanate, reaction

Hantzsch and Weber began their description with the compound which led them indirectly to the discovery of the thiazoles the a-thiocyanoacetone imine ( Rhodanpropimin ) of J. Tcherniac and C. H. Norton. C4H6N2S. obtained by reaction of ammonium thiocyanate with chloroacetone. After Tcherniac and Norton (18), the a thiocyanoacetone... 

The reaction is carried out at low temperature in aqueous medium and then allowed to stand overnight (221). Ammonium thiocarbamate is prepared from a cold saturated solution of ammonium thiocyanate, which is gradually added to dilute sulfuric acid at 25°C. The liberated carbonyl sulfide is passed into a saturated solution of alcoholic ammonia at about 10°C (221). The fairly low yield indicates that the reaction has not been greatly developed. 

Manufacture. An extensive technology was developed initially ia the 1930s for isolation of ammonium thiocyanate from coke-oven gases, but this technology is no longer practiced ia the United States (372). However, such thiocyanate recovery processes are used iadustrially ia Europe. Likewise, the direct sulfurization of cyanides to thiocyanates is not practiced commercially ia the United States. The principal route used ia the United States is the reaction of carbon disulfide with aqueous ammonia, which proceeds by way of ammonium dithiocarbamate [513-74-6]. Upon heatiag, the ammonium dithiocarbamate decomposes to ammonium thiocyanate and hydrogen sulfide. 

This reaction can also be mn in a continuous fashion. In the initial reactor, agitation is needed until the carbon disulfide Hquid phase reacts fully. The solution can then be vented to a tower where ammonia and hydrogen sulfide are stripped countercurrendy by a flow of steam from boiling ammonium thiocyanate solution. Ammonium sulfide solution is made as a by-product. The stripped ammonium thiocyanate solution is normally boiled to a strength of 55—60 wt %, and much of it is sold at this concentration. The balance is concentrated and cooled to produce crystals, which are removed by centrifiigation. 

Carbon disulfide reacts with concentrated ammonia to give ammonium thiocyanate [1762-95-4] and ammonium trithiocarbonate [13453-08-2] in a reaction promoted by alumina catalysts ... 

Thiooarbamide.—This is an example of a reversible reaction, in which either ammonium-thiocyanate or thiouiea when heated yields the same equilibiium mi.xttue. It may bo shown by melting a little thiourea for a minute, when the presence of thiocyanate is indicated by the addition of P eCl,. 

N-(2,6-dichiorophenyl)thiourea (MP 149°C) was prepared in customary manner from 2,6-dichloroaniline (Organic Synthesis lil, 262-263) and ammonium thiocyanate. 16.0 g of this thiourea derivative were refiuxed for 2 A hours together with 16 g of methyl iodide in 150 cc of methanol. Thereafter, the methanol was evaporated out of the reaction mixture in vacuo, leaving as a residue 22 g of N-(2,6-dichlorophenyl)-S-methyl-isothiouronium hydroiodide of the formuia... 

The following sections are concerned with the use of standard solutions of reagents such as silver nitrate, sodium chloride, potassium (or ammonium) thiocyanate, and potassium cyanide. Some of the determinations which will be considered strictly involve complex formation rather than precipitation reactions, but it is convenient to group them here as reactions involving the use of standard silver nitrate solutions. Before commencing the experimental work, the theoretical Sections 10.74 and 10.75 should be studied. 

FIGURE 6.9 The endothermic reaction between ammonium thiocyanate, NH4SCN, and barium hydroxide octahydrate, Ba(0H)2-8H20, absorbs a lot of heat and can cause water vapor in the air to freeze on the outside of the beaker. 

Alternatively, the reaction of 93c (R = n-Bu) with ammonium thiocyanate in refluxing acetic acid gave the ammonium salt of N-phosphonomethylthiohydantoin 99 in moderate isolated yield (2). 

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],... 

Introduction Melamine was isolated by Liebig in 1834 by separating reaction mixture obtained by heating ammonium thiocyanate. It was produced on a commercial scale in 1939. 

A favourable endothermic reaction occurs when barium hydroxide is mixed with ammonium thiocyanate. If you removed the stopper in photograph (B), you would detect the characteristic odour of ammonia. 

Certainly many favourable physical and chemical changes are exothermic. Some favourable changes, however, involve no release of energy. Others are actually endothermic. For example, a favourable endothermic chemical reaction occurs when barium hydroxide and ammonium thiocyanate are placed in an Erlenmeyer flask, as shown in Figure 7.4. 

Cyclohexylurea has been prepared by the reaction of cyclo-hexyl isocyanate with gaseous ammonia or ammonium hydroxide, by thermal decomposition of cyclohexyl allophanamide, by treating cyclohexylamine hydrochloride with an aqueous solution of potassium cyanate," by heating nitrosomethylurea with cyclohexylamine, and by heating an ethanolic solution of cyclohexylamine and 3,5-dimethyl-l-carbamylpyrazole. 2,6-DimethyIphenyIthiourea has been synthesized by allowing 2,6-dimethylaniline hydrochloride to react with ammonium thiocyanate. ... 

Acetazolamide Acetazolamide is 5-acetamido-l,3,4-thiadiazole-2-sulfonamide (9.7.5). The synthesis of acetazolamide is based on the production of 2-amino-5-mercapto-l,3, 4-thiadiazole (9.7.2), which is synthesized by the reaction of ammonium thiocyanate and hydrazine, forming hydrazino-N,N -( ji-(thiourea) (9.7.1), which cycles into thiazole (9.7.2) upon reaction with phosgene. Acylation of (9.7.2) with acetic anhydride gives 2-acetylamino-5-mercapto-l,3,4-thiadiazol (9.7.3). The obtained product is chlorinated to give 2-acetylamino-5-mercapto-l,3,4-thiadiazol-5-sulfonylchloride (9.7.4), which is transformed into acetazolamide upon reaction with ammonia (9.7.5) [24,25]. 

The chemistry of 1,4-(oxa/thia)-2-azoles, was founded in the late 1930s, when Musante first correctly suggested the 5-imino-2-phenyl 1,4,2-oxathiazole structure (1) for the product obtained from the reaction of ammonium thiocyanate and benzhydroximoyl chloride <38G33l>. Later, Beck described the preparation of dioxazolones (2) and some of their properties <51CB688>, while the first nonconjugated dioxazole derivative (3) was prepared by Exner from hydroxamic acid and benzophenone diethylacetal <56CLY779>. 

Ammonium thiocyanate is made in the United States by the reaction of carbon disulfide with aqueous ammonia. Ammonium dithiocarbamate is formed as an intermediate in this reaction, which upon heating, decomposes to ammonium thiocyanate and hydrogen sulfide. 

Zinc thiocyante is prepared by the reaction of ammonium thiocyanate with zinc hydroxide... 

The amount of ammonia volatilized was determined from the amount of standard sulfuric acid consumed in the traps. Ethylenediamine was determined by the salicylaldehyde method (14). The sample for cobalt(II) determination was made slightly acidic with hydrochloric acid immediately upon removal of the sample from the reaction flask, in order to prevent further oxidation of the cobalt (18). The carbon was removed by filtration, and the cobalt (II) concentration was determined spectrophotometrically as the cobalt-ammonium thiocyanate complex, (NH4)2Co(NCS)4 (28). 

Reaction of Iron(III) Chloride with Ammonium Thiocyanate. 

Pour 1-2 ml of an iron(III) chloride solution into each of two test tubes. Add several drops of an ammonium thiocyanate solution to one of the tubes, and a potassium hexacyanoferrate(II) (potassium ferrocyanide) solution to the other one. What happens Write the equations of the reactions. What are these reactions used for ... 

Another method of preparation consists in heating carbon disulphide with ammonium carbonate in a sealed tube. The other product of this reaction is ammonium thiocyanate. The yield of thiocarbamide by this method is stated to be much below the theoretical value.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). 

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