The role of small organic molecules in atmospheric chemistry and particle formation

Open Access
Author:
Goken, Erin Gabrielle
Graduate Program:
Chemistry
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
August 16, 2010
Committee Members:
  • Albert Welford Castleman Jr., Dissertation Advisor
  • Albert Welford Castleman Jr., Committee Chair
  • James Bernhard Anderson, Committee Member
  • John V Badding, Committee Member
  • James Hansell Adair, Committee Member
Keywords:
  • water
  • clusters
  • atmospheric chemistry
  • formic acid
Abstract:
Flow tube experiments were performed on two small organic molecules in order to determine the roles these chemicals play in the atmosphere, specifically solvation and particle growth. Research presented in this dissertation was performed using a fast-flow reactor at variable temperatures and pressures to mimic atmospheric conditions. This dissertation gives an introduction to the field of atmospheric chemistry and specifically water. The experimental method employed is described in detail, and the results of flow-tube studies of formic acid-water mixed clusters and methanol-water mixed clusters are compared. While methanol undergoes a switching reaction with water clusters, formic acid clearly causes growth of the water clusters. It is concluded that formic acid enhances the growth of water clusters. This hypothesis is examined further by theoretical calculations on small, neutral formic acid-water clusters as well as calculations on protonated clusters in the size range of 21 molecules. It was determined that formic acid strongly interacts with the hydrogen bonding network of the water clusters, altering the stability and ability to grow. In addition a theory for the stability of the magic water-21 cluster is presented. Bromoform and its anionic degradation products are examined; the solvation of the degradation products is shown as a function of temperature and relative pressure of bromoform and water. The solvation is more dependent on water than the ionic core of the cluster. The solvated ions are hypothesized to not be the dominate means of migration of halogen ions from the troposphere to the stratosphere. In addition, some interesting results of the cationic reaction of bromoform with water at room temperature are presented.