Sulphonic Derivatives of Hydrazine

The reaction between sulphuryl chloride, SO₂Cl₂, and dry ammonia gives under various conditions sulphamides and sulphimides. Some of these products were early prepared in an impure state.

In ligroin solution, trisulphimide (see table), sulphomelide (videinfra), and sulphamide are present. After removal of chloride with PbO, the silver salts of these compounds are precipitated in the order given, the last being that of sulphamide, which is then decomposed with the theoretical amount of HCl. The free sulphamide is recrystallised from hot alcohol. Or, the compound may be prepared in chloroform solution, the solvent then distilled, and the residue, dried at 100° C., is mixed with sand and extracted with ethyl acetate.

An entirely different method of making sulphamide by the decomposition of ammonium amido-sulphite has also been described.

The compound crystallises in colourless rhombic tables, melting at 91.5° to 93° C., easily soluble in cold water, hot methyl, or ethyl alcohols.

The molar weight in water corresponds to the formula SO₂.N₂H₄. At 100° C. it is decomposed with evolution of ammonia. In solution it is hydrolysed by acids to ammonium sulphate, by alkalies less completely, to salts of amido-sulphonic acid. The aqueous. solution does not react acid or conduct the electric current, but the hydrogen, while not ionised in solution, can be displaced with formation of salts. Thus the insoluble silver salt is precipitated by double decomposition. Mono- and di-potassium salts, SO₂N₂H₃K and SO₂N₂H₂K₂, are obtained by the reaction between the compound and potassium amide in liquid ammonia. Trisulphimide, (SO₂NH)₃, as a silver salt is the first fraction of the precipitate mentioned above. Esters are also known, but the free compound has only been prepared in solution. It is considered to have the formula



analogous to that of cyanuric acid, (OCNH)₃.

The ammonium salt of an isomeric compound, (SO₂NH)₃, is present in the residues after the distillation of ligroin from the products of the reaction which occurs between SO₂ and NH₃. The structure is said to be cyclic,



and analogous to that of cyamelide.

Imido-sulphamide (see table) is formed when the silver salt of tri- sulphimide is treated with H₂S. It appears as colourless crystals, melting at 160° C., which are soluble in ether, and in water, giving an acid solution from which ammonium, alkali, and silver salts can be obtained by displacement of the imino-hydrogen. It is also made from ammonium carbamate and pyrosulphuryl chloride.

Nitrilo-sulphonic acid or amino-trisulphonate, N(SO₃H)₃, has long been known in the form of its potassium salt, which is precipitated as crystals when a mixture of 1 mol. of KNO₂ and 3 mols. of K₂SO₃ is allowed to stand:

KNO₂ + 3K₂SO₃ + 2H₂O = N(SO₃K)₃ + 4KOH.

The sodium salt is formed when SO₂ is passed into a fairly concentrated solution containing 2 mols. of NaNO₂ and 3 mols. of Na₂CO₃.

It differs from the potassium salt in being more soluble and in crystallising with 5 mols. of water instead of with 2. These salts are hydrolysed quickly into the imido-, more slowly into the amido-, salts, especially in acid solution. Disodium imido-disulphonate is prepared by expelling the SO₂ from the above-mentioned sodium nitrilo-sulphonate by a current of air. The solution is then made slightly alkaline with Na₂CO₃ and evaporated. Sodium sulphate crystallises first, and then NH(SO₃Na)₂.