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A mode-selective differential scattering study of the C2H2 methanol reaction: Influence of collision intermediates, collision times,
 

Summary: A mode-selective differential scattering study of the C2H2 methanol
reaction: Influence of collision intermediates, collision times,
and transition states
Jun Qian, Richard J. Green, and Scott L. Anderson
Chemistry Department, University of Utah, 315 S. 1400 E. RM Dock, Salt Lake City, Utah 84112-0850
Received 9 December 1997; accepted 27 January 1998
We report the vibrational and collision energy dependence of cross sections and product branching
in the reaction of C2H2 with CD3OD, CD3OH, and CH3OD. We also report axial recoil velocity
distributions, along with modeling. At low collision energies, reaction is mediated by a picosecond
lifetime complex of the C2H2:methanol form. The bottleneck that controls overall reaction
efficiency appears to be formation of the complex, and reactivity is influenced by collision energy
and C2H2 CC stretch excitation, but not by bending vibration. The most energetically favorable exit
channel from the complex is isomerization to covalently bound C3H6O complexes, but this does
not occur. Instead the C2H2:methanol decays by breakup to C2H2 CH4O , C2H3 CH2OH ,
and C2H CH3OH2 channels. Changes in the branching with available energy provide some insight
into the nature of the transition states that control decay of the complex. As collision energy is raised
above 1 eV, the reaction gradually becomes direct, i.e., the collision time drops to well below the
rotational period of the collision complex ( 0.5 ps). In this regime, the dominant charge transfer
and hydride abstraction products mostly form in large impact parameter collisions. At high energies
there is little dependence of either reaction efficiency or product branching on collision energy or

  

Source: Anderson, Scott L. - Department of Chemistry, University of Utah

 

Collections: Energy Storage, Conversion and Utilization; Materials Science; Chemistry