The mass spectrum of allene (C3H4) is simulated by combining ab initio electronic structure calculations for predicting dissociation paths, RRKM theory to predict rate constant for each path, and solving the rate equations to obtain the fragment yields.  Isomerization of allene cations: C3H4+, C3H4+2, and C3H4+3, including hydrogen migration, carbon migration, cyclization, and ring opening, and their dissociations are sought and characterized with the unrestricted B3LYP/cc-pVTZ, in which the optimized geometries and harmonic frequencies of intermediates, transition states, and dissociation products are computed.  The energies are further refined by the coupled cluster CCSD(T)/cc-pVTZ with unrestricted B3LYP/6-311G(d,p) zero-point energy corrections.  The RRKM rate constant is then calculated for each elementary step which is adopted in the rate equations for the dissociation processes; subsequently, the fragment yields are obtained by solving the rate equations and utilized to simulate its mass spectrum.  The results are compared with the observed mass spectrum.

Simulation for mass spectrum of allene

243rd National Meeting (2012)

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