Study of the Vaporization Enthalpies by Correlation-Gas Chromatography

The focus of this thesis is on the measurement and collection of thermodynamic and physical property data, including vaporization, fusion, and sublimation enthalpies and vapor pressures of large n-alkanes, nitrogen heterocycles and related compounds by a technique developed in our laboratory referred to as correlation-gas chromatography (C-GC). These thermodynamic data are of importance to several disciplines that include chemical engineering, as well as the pharmaceutical and the petrochemical industries. Vapor pressures of large hydrocarbons are fundamental data required in the petroleum industry to develop thermodynamic models for dealing with crude oil. Environmental chemists and engineers use vapor pressures and vaporization enthalpies to model the dispersal of spills in the environment, such as the BP Gulf of Mexico oil spill, and to design chemical reactors. Alkanes are important components of petroleum. In the present work we have evaluated the vaporization enthalpies and vapor pressures of large n-alkanes with carbon chains up to 92 carbons by C-GC. These are the largest hydrocarbons ever evaluated with vaporization enthalpies that exceed the carbon-carbon bond strength and are good models for crude oil. Polyaromatic hydrocarbons (PAHs) are an important group of environmental contaminants that are produced by a variety of incomplete combustion processes. Polyaromatic nitrogen heterocycles (PANH’s) are their heterocyclic relatives that are also found environmentally in heavy petroleum. This study has also focused on the evaluation of the vaporization enthalpies and vapor pressures of PANH’s, most of which have not been previously reported. Finally, a study of aromatic diazines and diazoles (six- and five-membered heterocycles containing two nitrogen atoms, respectively), and related compounds has uncovered an interesting intermolecular interaction previously suspected but never measured. Our work has been able to assign a numerical value to this interaction. Since many biological molecules have similar structures, these interactions may be responsible for molecular association and signaling that occurs in such systems. The combination of planarity, polarity and extensive conjugation are common to all systems that appear to exhibit a higher degree of self-association