The photolysis of NH 3 in the presence of substituted acetylenes: A possible source of oligomers and HCN on Jupiter

Abstract

Photolysis of NH 3 in the presence of propyne yields dimethylketazine (4) as the main product along with dimethylketimine, isopropylamine, and propioazine (7). Dimethylketazine and isopropylamine are the principal reaction products when the protolysis is performed at 198 K. The conversion to dimethylketazine is about 35 times greater at 198 K because it is not volatile and condenses on the wall of the protolysis cell out of the UV flux. Protolysis of dimethylketazine at 185 nm yields acetonitrile and small amounts of N-methyldimethylketamine (8). Protolysis of 8 gives acetonitrile. Photolysis of NH 3 in the presence of 2-butyne gives the cis and trans isomers of 2-butane as the principal products along with the corresponding azine (9). Photolysis of azine 9 yields acetonitrile and propionitrile. Photolysis of hydrazine in the presence of propyne yields acetonitrile and isopropylamine but no azines were detected as reaction products. Quantum yields and percentage conversion to products are reported. These studies show that acetylenic hydrocarbons formed by the photolysis of methane in the stratosphere of Jupiter may react with radicals formed by NH 3 photolysis to give nonvolatile yellow-brown polymers, dialkylazines, alkylnitriles, and eventually HCN. This scenario accounts for the observation of both HCN and chromophores on Jupiter.