July 18, 2014
Writer: Brenda Pincock
Pinenes are a class of bicyclic molecules emitted by conifers and marine flora. These molecules constitute 6% of all biogenically derived volatile organic compound emissions in the atmosphere. Experimental research demonstrates that pinenes react with hydroxyl radicals via addition across the double bond. These, in turn, react with ambient oxygen to create pinene hydroxy-peroxy radicals. These species are stabilized by complexation with a water molecule. These reactions play a fundamental role in atmospheric chemistry. R-alpha and S-alpha pinene geometry optimizations for various stereoisomers of each radical and radical water complex were determined computationally at the B3LYP/6-311++G(2d,2p) method and basis set. Basis set superposition error was corrected using the counterpoise method. These calculation results were used to determine partition functions and calculate stereoisomer-specific equilibrium constants. The present work focuses on deducing Boltzmann-weighted average global equilibrium constants for the hydroxy-peroxy pinene-water complexes based on the stereoisomer-specific results.