Reactions of NH Radicals. III. Photolysis of HN3 in the Presence of C2H4 at 313 nm

Photolysis of HN3 vapor in the presence of C2H4 was studied at 313 nm and 30 °C. The main products were N2, H2, CH4, C2H6, NH4N3, C2H5N·HN3 (salt of C2H5N (azomethines) with HN3), HCN, CH3CN, CH3N3, and C2H5N3. The quantum yields of these products were measured as a function of the light intensity and pressures of HN3 and C2H4. The following mechanism for the main reactions was infered: HN3+hν(313 nm)→NH(a1Δ)+N2; NH(a1Δ)+HN3→2N2+2H (2a); NH(a1Δ)+HN3→NH2+N3 (2b); NH(a1Δ)+HN3→N2+N2H2* (2c); NH(a1Δ)+C2H4→C2H5N* (aziridine and vinylamine) (3); C2H5N*→CH3+CH2N (4); C2H5N*→H2+CH3CN (5); C2H5N*→H+C2H4N (6); C2H5N*→C2H3+NH2 (7). The rate constant ratios at 30 °C are: k3⁄k2=1.64; k5⁄k4=0.102; k6⁄k4=0.564; k7⁄k4=0.734. The collisional deactivation from NH(a1Δ) to NH(X3Σ−) by C2H4 was not found. The lifetime of C2H5N* is much shorter than 6.8×10−11 s for C2H5NH2*(←NH(a1Δ)+C2H6). The relative and absolute rates for the reactions of NH(a1Δ) with HN3, Xe, C2H6, and C2H4 are discussed.