Thermal decomposition of energetic materials 76. Chemical pathways that control the burning rates of 5-aminotetrazole and its hydrohalide salts

The hydrohalide (HCl, HBr, HI) salts of 5-amino-1H-tetrazole (5-ATZ) were flash pyrolyzed under 0.5 MPa of Ar by T-jump/FTIR spectroscopy, and the gaseous products were determined at 350 degrees C, 400 degrees C, and 450 degrees C. Comparison of the products indicated that two global decomposition pathways exist, which give somewhat different products. The first channel is dissociation of the salt to form HX and 5-ATZ followed by decomposition of neutral 5-ATZ. The second channel involves decomposition of the [5-ATZ](+) ion directly. The ratio of these two channels depends on the compound. The first channel is favored over the second channel in the order HCl > HBr > HI, which is the trend of the pK(a) values of these acids. This information enables both the ordering of the burning rates as a function of pressure as well as the trend in the pressure dependence of the individual burning rates of these compounds to be rationalized. (C) 2000 by The Combustion Institute.