Reaction of cyanogen and hydrogen behind reflected shock waves

Abstract

The metathetical reaction, C2N2 + H2 <=r 2HCN, has been studied by shocking equimolar amounts of the reactants in the presence of an inert gas diluent over the temperature range 1850-2650°K. A complementary shock tube facility was utilized to obtain the data from the reflected shock zone by recording the infrared emission of HCN and the time-resolved mass spectra at m/e 27 (HCN) and 52 (C2N2). The total density variation was 1.8-4.4 X 10~8 mol/cm3. Observation times were typically 500 psec during which period an equilibrium condition was established for the higher temperature experiments. The growth of the mole fraction of HCN, /hcn, was found to be a nonlinear function of time and to depend upon the inert gas concentration, [M]. The data from the two independent techniques of infrared emission and mass spectrometry were fitted to the bimolecular rate expression that includes the back reaction, In |[(X -4)/Hcn -(X + 2X1/2)]/[(X-4)/HCn -(X -where the forward rate constant is given by fci = 102®-3S±0-21 exp(-61,610 ± 2010/RT) cm3 mol-1 sec-2 [M]-°-75. These results rule out the direct bimolecular reaction. This complex reaction is discussed in terms of an atomic mechanism and a mechanism involving vibrationally excited species. Experiments on an equimolar mixture of cyanogen and deuterium revealed a lowering of the preexponential factor in reasonable agreement with that predicted from the square root of the inverse ratio of reduced masses.

Mid-infrared Frequency Modulation Detection of HCN and Its Reaction with O Atoms behind Shock Waves

“…Reports on spectroscopic detection of HCN behind shock waves are scarce. In early work of Brupbacher and Kern, , who recorded the first kinetic profiles of HCN (and DCN) behind shock waves by detecting the CH stretch band emission centered at 3.0 ± 0.1 μm (mostly referred to as the ν 1 band), equimolar mixtures of 1–2% HCN/D 2 or C 2 N 2 /H 2 in argon were shock-heated to investigate the isotope exchange mechanism and the formation of HCN, respectively. Later, Chang and Hanson investigated the pressure broadening of the P(10) line in the ν 1 band using tunable diode laser spectroscopy.…”