A Shock Tube Laser Schlieren Study of Nitromethane Dissociation: Looking for the Isomerization Channel

摘要

Previous experimental determinations of the dissociation rate of nitromethane (CH_3NO_2) have only considered a single pathway involving C-N bond breakage. However, there is also some experimental evidence that a second channel with isomerization to methyl nitrite is possible. Recent theoretical work has shown this isomerization may involve a roaming type transition. To determine if this channel is important shock tube laser schlieren experiments on pyrolysis of 2% nitromethane in krypton at 120 Torr between 1226 and 1734 K were performed. Laser schlieren is well suited for this study as each reaction channel has substantially different enthalpies of reaction and the experiments are sensitive to the branching ratio between the two channels. An RRKM model for the primary dissociation is developed that compares well to previous experimental results for the C-N bond breakage. Modeling of the data requires that approximately 15% of the nitromethane isomerizes prior to dissociation under the conditions of this study, showing that isomerization can be important in this system.