5-Tetrazole diazonium chloride

Diazotised 5-aminotetrazole is unstable under the conditions recommended for its use as a biochemical reagent. While the pH of the diazotised material (the cation of which contains 87% nitrogen) at 0°C was being reduced to 5 by addition of potassium hydroxide, a violent explosion occurred [1], This may have been caused by a local excess of alkali causing the formation of the internal salt, 5-diazoniotetrazolide, which will explode in concentrated solution at 0°C [2], The diazonium chloride is also very unstable in concentrated solution at 0°C. Small-scale diazotisation (2 g of amine) and susequent coupling at pH 3 with ethyl cyanoacetate to prepare ethyl 2-cyano-(l//-tetrazol-5-ylhydrazono)acetate proceeded uneventfully, but on double the scale a violent explosion occurred [3], The importance of adequate dilution of the reaction media to prevent explosions during diazotisation is stressed [4]. 

Potassium 1-phenylethanediazoate, 2964 Tetrazole-5-diazonium chloride, 0370 2-Toluenediazonium bromide, 2736... 

Tetrazirconium tetraoxide hydrogen nonaperchlorate, 4189 Tetrazole-5-diazonium chloride, 0369 Tetrazole, 0410a... 

Tetrazole-5-diazonium chloride, 0369 5 -Trichloromethyl-1 -trimethylsilyltetrazole, 1921 5-Trichloromethyltetrazole, 0653 See other HIGH-NITROGEN COMPOUNDS... 

Aromatic diazonio groups may be mentioned her due to their — at least formal -similarity to nitrile groups. In 1955 Huisgen and Koch investigated the reaction of 4-nitrobenzenediazonium chloride with an excess of diazomethane. They found that diazomethane reacts as a C-nucleophile in an azo coupling reaction (see Zollinger, 1994, Sect. 12.6, p. 339). In ether, 12% of l-(4-nitrophenyl)-l//-tetrazole (6.102) was, however, also found and Reimlinger et al. (1970) isolated l-(l//-pyrazol-5-yl)-li/-tetrazole (6.103) in 24% yield from pyrazole-3-diazonium chloride and diazomethane. 

Diazotetrazole (16) was obtained by dropwise addition of 2-pentyl nitrite to a solution of 5-amino-l//-tetrazole in a 4 1 mixture of tetrahydrofuran and aqueous hydrochloric acid. The diazonium chloride can be extracted into ether. Shevlin obtained the extremely explosive solid diazonium salt (16) by evaporation of that solution. He has recommended that not more than 0.75 mmol of diazonium salt be isolated at one time. An explosion during the diazotization of 5-aminotetrazole on a laboratory scale was described by Gray and coworkers. The structure 17 (equation 5) indicates clearly that this diazo compound may have the tendency to decompose into atomic carbon and three equivalents of dinitrogen—a reaction which is clearly highly exothermic. The decomposition of the tetrazole-5-diazonium chloride (16) has been studied by Shevlin by coating the salt on the walls of a 500 ml flask in the presence of two substrates, ethene and ethylene oxide. With ethene the products found after heating the flask to 80 °C are shown in equation 6, and with ethylene oxide in equation 7. The products correspond to those found with atomic carbon formed by completely different methods (see references cited by Shevlin). 

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