Quasiclassical Trajectory Calculations of the Dissociation Dynamics of CH3CHO at High Energy Yield Many Products

We present a quasiclassical trajectory study of the photodissociation of CH3CHO using a global ab initio-based potential energy surface. Calculations are performed at a total energy of 160 kcal/mol, corresponding to a photolysis wavelength of 230 nm, and with all trajectories initiated from the acetaldehyde global minimum. Many product channels are energetically accessible and observed at this energy, and the branching ratios to these are presented. We identify a minor channel giving H2O plus vinylidene or acetylene. Mechanisms are identified for these products, both of which originate from dissociation of vinyl alcohol an isomer of acetaldehyde. The channel CH2=CHOH -> HCCH + H2O produces acetylene with relatively low internal energy, while the acetylene which arises from the subsequent isomerization of vinylidene via the channel CH2=CHOH -> [CH2=C + H2O] -> HCCH + H2O, is highly excited. The dissociation of CD3CHO is also studied, and both HOD+DCCD (D2CC) and D2O+DCCH products are formed from the same mechanisms as in the CH3CHO dissociation.