Preparation of tetrazolone
A mixture consisting of 10.3 g (0.1 mol) of 5-aminotetrazole 1-hydrate in 200 ml of water, 10 ml of concentrated sulfuric acid, and 100 g of ice was cooled by stirring to below 5° C by completely immersing the reaction vessel in crushed ice. A solution of 7.6 g (0.11 mol) of sodium nitrite in 50 ml of water, cooled to 5° C, was added to the stirred solution at a fairly rapid rate. Very little, if any, the temperature rise was observed. The reaction mixture was stirred at 5° C for 30 minutes and a cooled solution of 37.0 g (0.15 mol) of copper sulfate 5-hydrate in 200 ml of water was added. Stirring was continued for an additional 30 minutes and the reaction mixture was refrigerated overnight at 5° C. A small amount of precipitate which had separated was collected by filtration, dissolved in 10 ml of concentrated hydrochloric acid, and added to the original nitrate. Hydrogen sulfide was bubbled through the solution for 10 minutes and the precipitated copper(II) sulfide was removed by filtration. The hydrogen sulfide treatment was twice repeated to remove any residual copper ions. The filtrate was heated on the steam bath and 81.0 g (0.33 mol) of barium chloride 2-hydrate was added with rapid stirring. The precipitated barium sulfate was removed by filtration and the filtrate was evaporated to dryness on the steam bath with the aid of an air stream. The residue was further dried to yield 4.78 g of the final product, which melts at 250 to 251° C (with dec.). Two more recrystallizations from water gave 3.25 g. (38%) of tetrazolone having a melting point of 257-258° C (dec). Three subsequent recrystallizations from water did not raise the melting point.
Inorganic Syntheses, Vol. 4, 1960, 62-65.
5-Hydroxtetrazole, 1H-Tetrazol-5-ol, 16421-52-6, 5-Hydroxytetrazole, 1,2-dihydrotetrazol-5-one, AC1L3G64, 5H-Tetrazol-5-one,4-dihydro-, CTK4D1750, CTK8H1735, 5H-Tetrazol-5-one,1,2-dihydro-, NSC338114, AKOS006311783, NSC-338114, 1,4-DIHYDRO-5H-TETRAZOL-5-ONE