Reactions with Elements and Element Ions

Noble Gases. Flames of HN3 and electronically excited Ar, Kr, or Xe emit strong bands of rotationally excited NH(A 11). Additional bands of N2(B Ilg) are found in flames with Ar and Kr [1]. 

Hydrogen. Spark ignition of HN3 in excess H2 yields more NH3 than expected for the decomposition of HN3 into NH3 and N2. This indicates an interaction between the starting materials [2]. 

Flames of HN3 and H atoms in flow systems at total pressures less than 4 Torr are bright yellow with orange edges [3]. At ambient temperatures the reaction of the gases is quite fast [4] fast freezing of the products yields a blue solid which resembles the product from incomplete decomposition of HN3 [5] see also p. 120. The reaction of frozen HN3 and H atoms at 77 K is very slow [6]. 

The reaction of HN3 or DN3 with H atoms is best described in terms of a thermal decomposition of hydrazoic acid, induced by the heat liberated during recombination of the H atoms [7, 8]. Initial products are NH and ND in the A 11 state, indicative of excitation of hydrazoic acid to the triplet state before decomposition [7]. The rotational temperature of NH(A 11) in the 5500 K range causes the chemiluminescence of this reaction [3]. Emissions of NH [9] and ND [8] in the c state, NH(b [10], NH2 [9] and its deuterated isotopomers [7], N2(a Z) [11], and N2(C 11 ) [12] were also observed and are supposed to result from secondary reactions. The rotational temperature of NH( IT) of - MOO K also is its flame temperature [3]. The electronically excited NH2(A Ai) is in the vibrational states V2 = 9 to V2 = 15 [10]. 

The reaction of HN3 with less than the equimolar amount of H atoms in a flow system yields N2 and H2- Assuming a bimolecular reaction, a rate constant of k= (6.4 2.0) x 10 cm molecule -s was determined at ambient temperature [13]. The reaction of HN3 with excess H atoms yields up to 40% of NH3 with respect to reacted HN3 in addition to N2 and H2. The reaction rate increases with the concentration of H the rate constant is 1.53 X 10 exp[ - (19.2 1.3) kJ morVRT] cm mol s in the temperature range 300 to 460 K. The activation energy indicates HN3 H- NH2 +N2 to be the initial reaction [14]. Calculations of the structure of the supposed intermediate N3H2 are described on p. 156. The first-order dependence of the NH2 emission on the concentrations of HN3 and H suggests exclusive formation of NH2 by this reaction [10]. 

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