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A Scalable Balz-Schiemann Reaction Protocol in a Continuous Flow Reactor
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A phase space theory for roaming reactions.

Duncan U Andrews1, Scott H Kable, Meredith J T Jordan

  • 1School of Chemistry, University of Sydney, NSW 2006, Australia.

The Journal of Physical Chemistry. A
|June 19, 2013
PubMed
Summary
This summary is machine-generated.

A new theory predicts product branching in roaming reactions by analyzing reactive states. This phase space theory (PST) approach accurately models roaming versus bond dissociation for H2CO, NO3, and CH3CHO.

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Area of Science:

  • Chemical Kinetics
  • Theoretical Chemistry
  • Physical Chemistry

Background:

  • Roaming reactions are a complex class of chemical reactions where dissociation products follow indirect pathways.
  • Predicting the branching fraction between roaming and direct bond dissociation products is crucial for understanding reaction dynamics.
  • Existing theories often struggle to accurately model the competition between roaming and barrierless bond dissociation.

Purpose of the Study:

  • To introduce a new, simple theory for predicting product branching fractions in roaming reactions.
  • To compare the outcomes of roaming reactions with analogous barrierless bond dissociation products.
  • To validate the new theory against experimental and theoretical data for specific molecular systems.

Main Methods:

  • Development of a phase space theory (PST) formalism to categorize reactive states in the bond dissociation channel.
  • Division of states into those with sufficient translational energy for dissociation and those capable of roaming.
  • Introduction of two key parameters: ΔEroam (energy difference between dissociation and roaming thresholds) and Proam (roaming probability).

Main Results:

  • The PST-roaming theory accurately models the relative branching fraction of roaming to bond dissociation products for H2CO, NO3, and CH3CHO.
  • For H2CO, the theory aligns with experimental bounds for ΔEroam and predicts similar branching ratios for D2CO and H2CO.
  • For NO3, the theory accurately predicts low-temperature branching fractions and NO yield spectra with a small Proam (0.0075).
  • For CH3CHO, the theory, using theoretically calculated ΔEroam and a fitted Proam (0.21), is consistent with experimental data.

Conclusions:

  • The developed PST-roaming theory provides a simple yet accurate method for predicting product branching in roaming reactions.
  • The theory successfully quantifies the competition between roaming and direct bond dissociation pathways across different molecular systems.
  • This theory, combined with other kinetic theories, can yield rate coefficients for roaming reactions, advancing chemical dynamics understanding.