Clarifying mechanisms and kinetics of programmable catalysis.

Programmable catalysis-the purposeful oscillation of catalytic potential energy surfaces (PES)-has emerged as a promising method for the acceleration of catalyzed reaction rates. However, theoretical study of programmable catalysis has been limited by onerous computational demands of integrating the stiff differential equations that describe periodic cycling between PESs. This work details methods that reduce the computational cost of finding the limit cycle by ≳10×.

Concepts Relevant for the Kinetic Analysis of Reversible Reaction Systems.

The net rate of a reversible chemical reaction is the difference between unidirectional rates of traversal along forward and reverse reaction paths. In a multistep reaction sequence, the forward and reverse trajectories, in general, are not the microscopic reverse of one another; rather, each unidirectional route is comprised of distinct rate-controlling steps, intermediates, and transition states. Consequently, traditional descriptors of rate (e.

Kinetic description of site ensembles on catalytic surfaces.

We demonstrate that the Langmuir-Hinshelwood formalism is an incomplete kinetic description and, in particular, that the Hinshelwood assumption (i.e., that adsorbates are randomly distributed on the surface) is inappropriate even in catalytic reactions as simple as A + A → A The Hinshelwood assumption results in miscounting of site pairs (e.

Henry's Constants of Persistent Organic Pollutants by a Group-Contribution Method Based on Scaled-Particle Theory.

A group-contribution method based on scaled-particle theory was developed to predict Henry's constants for six families of persistent organic pollutants: polychlorinated benzenes, polychlorinated biphenyls, polychlorinated dibenzodioxins, polychlorinated dibenzofurans, polychlorinated naphthalenes, and polybrominated diphenyl ethers. The group-contribution model uses limited experimental data to obtain group-interaction parameters for an easy-to-use method to predict Henry's constants for systems where reliable experimental data are scarce. By using group-interaction parameters obtained from data reduction, scaled-particle theory gives the partial molar Gibbs energy of dissolution, Δg̅, allowing calculation of Henry's constant, H, for more than 700 organic pollutants.