Preparation of thiocyanogen
Alternative Names: Dicyano disulfide; Thiocyanato thiocyanate; Cyanodisulfanyl-nitrido-methane; 505-14-6; NCSSCN;
A solution of thiocyanogen is obtained by adding somewhat less than the theoretical amount of bromine (as 10% solution) to a suspension of lead thiocyanate (lead thiocyanate could be prepared from lead nitrate and NaSCN in cold water) in dry ether, light petroleum, carbon disulfide, benzene, chloroform, carbon tetrachloride, or glacial acetic acid, with shaking and cooling to 5-10° C. The resulting colorless and clear solution is decanted. Thiocyanogen should be prepared as shortly as possible before its use as it polymerizes readily at room temperature to a red amorphous product. It is more stable in solution but polymerizes there too particularly under the influence of light, heat, moisture, or oxygen.
Anhydrous acetic acid containing some acetic anhydride provides the most stable thiocyanogen solutions. Very pure lead thiocyanate is shaken in the dark with bromine in a mixture of 6 parts by volume of acetic acid (distilled from 1 % of chromic trioxide), 1 part by volume of acetic anhydride, and 3 parts by volume of pure anhydrous carbon tetrachloride, all contained in dry vessels that give up no alkali, i.e., that have been previously boiled out with hydrochloric acid. Filtration of the mixture through a dry filter, with exclusion of moisture, gives clear thiocyanogen solutions that are stable for several weeks.
It is advantageous to use nascent thiocyanogen; for instance, bromine is added to a cooled solution of the organic compound and an alkali thiocyanate in methanol, acetone, methyl acetate, or glacial acetic acid. Moreover, the copper thiocyanate process provides another method of working with nascent thiocyanogen. The organic compound is treated in an organic solvent (methanol, ethyl acetate, or glacial acetic acid) or in an aqueous acid with the black copper(II) thiocyanate (Cu(SCN)2) which can be produced during the reaction from a copper(II) salt and an alkali or ammonium thiocyanate:
2Cu(SCN)2 → 2CuSCN + (SCN)2
The thiocyanogen is continuously consumed, as becomes recognizable by the decoloration to white copper(I) thiocyanate (CuSCN).
Org. Reactions, 3, (a) 241, (b) 285 (1946);
Ann. Chem., 419, 217 (1919);
Ber. Deut. Chem. Ges., 62, 390 (1929);
Arch. Pharm., 267, 201 (1929);
Thiocyanogen, Dicyano disulfide, thiocyanato thiocyanate, cyanodisulfanyl-nitrido-methane, 505-14-6, NCSSCN, Dirhodan, disulfanedicarbonitrile, AC1Q4SR1, SCHEMBL432381, UNII-9ME5949L1M, AC1L295Y, (cyanodisulfanyl)(nitrilo)methane, CHEBI:30063, CTK8I9196, 9ME5949L1M, bis[(cyanido–C)sulfur](S–S), IN015942