Thiocyanic acid

A solution of 100 g. (0.47 mole) of ethyl o-tolyl xanthate in 300 g. of ethanol is treated gradually with 100 g. of solid potassium hydroxide, and the resulting mixture is held at the boiling point for 8 hours. The mixture is diluted with water and extracted with ether. The resulting clear aqueous solution is acidified by the slow addition of dilute sulfuric acid. The mixture is steam-distilled after the addition of 3-4 g. of powdered zinc, and the organic product is separated from the distillate by ether extraction. Distillation of the ethereal solution gives an 81% yield (based on o-toluidine). o-Thiocresol boils at 106°/50 mm. and 194°/760 mm. 

NH4CNS + H2S04 - HCNS + (NH4)HS04 Gluud, Keller, and Klempt, Bex., 59, 1386 (1926). 

---

In 1887 (57) and 1889 (73) Andreasch confirmed the cyclic formula proposed by Liebermann and Lange (20). Freydl (74) obtained rhodaninic acid by condensing thioglycolic acid with thiocyanic acid. 

Examples SCN (thiocyanate), HSCN (hydrogen thiocyanate or thiocyanic acid), HNCO (hy-... 

Antino-2-thiazolines are formed from thiocyanic acid [463-56-9] and aziridines where R = H or CH (116,134). 

Free thiocyanic acid [463-56-9] HSCN, can be isolated from its salts, but is not an article of commerce because of its instabiHty, although dilute solutions can be stored briefly. Commercial derivatives of thiocyanic acid are principally ammonium, sodium, and potassium thiocyanates, as weU as several organic thiocyanates. The chemistry and biochemistry of thiocyanic acid and its derivatives have been reviewed extensively (372—374). 

In the initial thiocyanate-complex Hquid—Hquid extraction process (42,43), the thiocyanate complexes of hafnium and zirconium were extracted with ether from a dilute sulfuric acid solution of zirconium and hafnium to obtain hafnium. This process was modified in 1949—1950 by an Oak Ridge team and is stiH used in the United States. A solution of thiocyanic acid in methyl isobutyl ketone (MIBK) is used to extract hafnium preferentially from a concentrated zirconium—hafnium oxide chloride solution which also contains thiocyanic acid. The separated metals are recovered by precipitation as basic zirconium sulfate and hydrous hafnium oxide, respectively, and calcined to the oxide (44,45). This process is used by Teledyne Wah Chang Albany Corporation and Western Zirconium Division of Westinghouse, and was used by Carbomndum Metals Company, Reactive Metals Inc., AMAX Specialty Metals, Toyo Zirconium in Japan, and Pechiney Ugine Kuhlmann in France. 

In an analogous manner, DCPD reacts with alcohols and phenols to form ether derivatives, and with halogen acids, thiocyanic acid, and various carboxyhc acids to form esters. These esters are used as perfume components (67). Dicyclopentadiene alcohol and a number of the ethers, esters, and glycol adducts have been claimed as coal and ore flotation aids (68). 

Aziridines also undergo ring enlargement when treatment with thiocyanic acid, cis- and tran5-2,3-Dimethylaziridine (470) with thiocyanic acid gave exclusively trans- and cis-1-amino-4,5-dimethyl-2-thiazoline (471) (72JOC4401). 

Certain bifunctional nucleophiles allow cyclization after ring opening. The formation of 2-thiazolium salts (71JHC40S) and the analogous production of 2-amino-2-thiazolines (191) from aziridines and thiocyanic acid fall into this category (72JOC4401). 

The use of thiocyanic acid for thiirane synthesis is usually compatible with many functional groups found in natural steroids. The method has found application in androstanes, pregnanes, cholestanes, cholanates and cardeno-lides. However, the presence of a,j5-unsaturated carbonyl groups may decrease the yield of the thiocyanatohydrin due to conjugate addition of thiocyanic acid. Indeed, the 1,4-addition of thiocyanic acid has been carried... 

A decisive solvent effect is also observed with other a,/ -epoxy ketones. Specifically, 3jS-hydroxy-16a,17a-epoxypregn-5-en-20-one and its acetate do not react with thiocyanic acid in ether or chloroform. However, the corresponding thiocyanatohydrins are formed by heating an acetic acid solution of the epoxide and potassium thiocyanate. As expected, the ring opening reaction is subject to steric hindrance. For example, 3j6-acetoxy-14f ,15f5-epoxy-5) -card-20(22)-enoIide is inert to thiocyanic acid in chloroform, whereas the 14a,15a-epoxide reacts readily under these conditions.Reactions of 14a,15a-epoxides in the cardenolide series yields isothiocyanatohydrins, e.g., (135), in addition to the normal thiocyanatohydrin, e.g., (134). 

To the epoxide dissolved in a minimal amount of chloroform or ether is added a corresponding solution of freshly prepared thiocyanic acid (20 fold excess) as described above (acetic acid has also been used as solvent). The resulting solution is allowed to stand at least 70 hr at room temperature. (Some workers have protected the reaction mixture from light during this period). The reaction mixture is worked up by washing first with a 10% solution of sodium carbonate, sodium bicarbonate or potassium bicarbonate, and then water. The remaining ether extract is dried (Na2S04) and evaporated under vacuum. The crude thiocyanatohydrin is crystallized from an appropriate solvent or treated with methanesulfonyl chloride s (see below). 

Thiocyanates and selenocyanates can be made by fusing the corresponding cyanide with S or Se. The SCN and SeCN ions are both linear, like OCN . (See p, 779 for TeCN ) Treatment of KSCN with dry KHSO4 produces free isothiocyanic acid HNCS, a white crystalline solid which is stable below 0° but which decomposes rapidly at room temperatures to HCN and a yellow solid H2C2N2S3. Thiocyanic acid, HSCN, (like HOCN) has not been prepared... 

A. A. Newman (ed.). Chemistry and Biochemistry of Thiocyanic Acid and its Derivatives, Academic Press, London, 1975, 351 pp. 

Blut rot, n. hemoglobin hematin, ruhr, /. dysentery. s ure, /, thiocyanic acid. 06s, scheibe, /. blood corpuscle. schlag, m. apoplexy. seuche, /. anthrax. stein, m. bloodstone, hematite. 

Rhodan-verbindtmg, /. thiocyanogen compound. -wasserstoff, m. hydrogen thiocyanate, thiocyanic acid, -wasserstoffskure, /. thiocyanic acid, (formerly) sulfocyanic acid, -zlnn, -zinnozyd, n. stannic thiocyanate, tinilV) thiocyanate, -zinnoiydul, n. stannous thiocyanate, tin (II) thiocyanate. 

Schwefel-cyanwasserstoffsaure, /. thiocyanic acid, -dampf, m. sulfur vapor, -dioxyd, n, sulfur dioxide, -dunst, m. sulfurous vapor, schwefelecht, a. (Dyeing) fast to stoving, fast to sulfurous acid. 

Sulfocyankalium, n. potassium thiocyanate, sulfocyansauer, a. of or combined with sulfo-cyanic (thiocyanic) acid, sulfocyanate (thio cyanate) of. 

Thiocyan-saure, /. thiocyanic acid, -verbin-dung, /. thiocyanate. 

N 24.12% brick red solid mp, decomps when heated over 300°. Insol in w and the usual organic solvents as well as weak acids and alkalies. Comm prepn (Ref 3) is from thiocyanic acid and/or thiocyanates either by anodic oxidation or by interaction with hydrogen peroxide or halogens. The yield is impure because it contains both H and O. The S content varies between 45 and 55%. Lab prepn of the pure polymer is by reacting the Na salt of 5-chlor-3-mercapto 1,2,4-thiodiazols with either acet, ethanol or w (Refs 1 2)... 

C7H,jOS 98-91-9) see Stepronin 3a-thiocyanato-5a-androstane-2f),l 7P-diol 17-acetate (C22H33NO3S 2469-96-7) see Epitiostanol thiocyanic acid... 

The dearrangement of phenylthiourea may be demonstrated very simply by heating a small quantity of the material in a test-tube. It undergoes a violent decomposition slightly above its melting-point, the odors of ammonia, of aniline, and of phenyl mustard oil may be detected, and the residue which consists largely of sym.-diphenylthiourea gives with ferric chloride the a ed color characteristic of thiocyanic acid. 

Supplement (combined with Volume IV) III, 2nd 1929 195-449 Hydroxy-carboxylic acids Carbonic acid, 3. GlycoUic acid, 228. Lactic acid, 261. Tartaric acid, 481. Citric acid, 556. Urea, 42. CyS namide, 74. Thiocyanic acid, 140. 

Amidation, of thiocyanic acid with o-chloroaniline, 31, 21 Amino acid, 30, 7 -Ahinobenzaldehyde, 31, 6 -Aminobenzaldehyde hydrazone, 31, 7 / -Aminobenzaldehyde oxime, 31, 7 -Aminobenzaldehyde phenylhydra-zone, 31, 7... 

---