Reactions of NH Radicals. V. Photolysis of HN3 in the Presence of C3H8 at 313 nm

The photolysis of HN3 vapor in the presence of C3H8 was studied at 313 nm and 30°C. The main products were N2, H2, CH4, C2H6, C3H6, NH4N3, CH3NH2·HN3, C2H5NH2·HN3, and n- and i-C3H7NH2·HN3. The quantum yields of these products were measured as a function of the pressure of HN3 or C3H8. The following mechanisms for the main reactions was proposed: HN3+hν(313 nm)→N2+NH(a1Δ); NH(a1Δ)+HN3→2N2+2H, NH2+N3, and N2+N2H2* (2); NH(a1Δ)+C3H8→C3H7NH2*(n- and i-propylamine) (3); NH(a1Δ)+C3H8→NH (X3Σ−)+C3H8 (4); C3H7NH2*→CH3+C2H4NH2 (5); CH4+C2H4NH (6), C2H4+CH3NH2 (7), C2H5+CH2NH2 (8), C2H6+CH2NH (9), H2+C3H6NH (10), and NH3+C3H6 (11); C3H7NH2*+HN3→C3H7NH2+HN3 (12); C3H7NH2*+ C3H8→C3H7NH2+C3H8 (13). The rate constant ratios are: k3⁄k2=1.28; k4⁄k2=0.262; k6⁄k5=0.109; k7⁄k5=0.050; k8⁄k5=1.39; k9⁄k5=0.040; k10⁄k5=1.20; k11⁄k5=4.72; k12⁄k5=666 dm3 mol−1; k13⁄k5=860 dm3 mol−1. The formation ratio of n-C3H7NH2/i-C3H7NH2 was 1.55, regardless of the total pressure. The half-life of 1.78×10−10 s for C3H7NH2* was obtained by using the collision theory. The relative and absolute rate constants were compared for the reactions of NH(a1Δ) with CH4, C2H6, and C3H8; it was found that the relative yield for the insertion of NH(a1Δ) into a C–H bond increases with a decrease in the C–H bond dissociation energy.