Techn. Hochsch., Diss.--Aachen, 2006.

published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

The UPPER (Unified Physicochemical Property Estimation Relationships) model uses additive and non-additive parameters to estimate 21 biologically and environmentally important physicochemical properties of organic compounds. Thermodynamically sound relationships are used to predict boiling and melting points, aqueous and octanol solubilities, vapor pressure and the air-octanol, air-water and octanol-water partition coefficients. These properties determine the distribution and fate of organic compounds in biological and environmental systems. The model has been validated on a data set of 2000 hydrocarbons and polyhalogenated hydrocarbons, provides a simple and accurate method to predict the properties studied.

Melting point finds applications in chemical identification, purification and in the calculation of a number of other physicochemical properties such as vapor pressure and aqueous solubility. Despite the availability of enormous amounts of experimental data, no generally applicable methods have been developed to estimate the melting point of a compound from its chemical structure. A quick estimation of melting point can be a useful tool in the design of new chemical entities.In this dissertation, a simple means of estimating the melting points for a large variety of pharmaceutically and environmentally relevant organic compounds is developed. Melting points are predicted from the separate calculation of the enthalpy and entropy of melting directly from the chemical structure. The entropy of melting is calculated using a semi-empirical equation based on only two non-additive molecular parameters. This equation is validated and refined using a large collection of experimental entropy of melting values. The enthalpy of melting is calculated by additive group contributions.Melting points are estimated from the ratio of the enthalpy of melting and the entropy of melting. All of the methods and group contributions developed in this study are compatible with the UPPER (Unified Physical Property Estimating Relationships) scheme. The predicted melting points are compared to experimental melting points for over 2200 organic compounds collected from the literature. The average absolute error in melting point prediction is 30.1 °. This is a very reasonable estimate considering the size and diversity of the dataset used in this study.

This investigation focuses on two well-preserved impact structures developed in sedimentary target rocks: the ~23.5 Ma old Haughton structure, Canada, and the ~14.5 Ma old Ries structure, Germany. The aim of this study was to investigate the effects of hypervelocity impact into sedimentary targets. The study reveals that a series of different impactites are present at Haughton, the bulk of which comprise a groundmass of impact-generated melts (calcite + silicate glass ± anhydrite). Thus, carbonates, evaporites, sandstones, and shales underwent shock melting during the Haughton impact event. The shock melting of impure carbonates resulted in the generation of Mg–Ca–Si-rich melts that crystallized calcite during rapid cooling. The residual melt quenched to Mg–Si-rich glass. These impactites should, therefore, be classified as clast-rich impact melt rocks or impact melt breccias, and not clastic matrix breccias as previously held. Ries surficial suevites are reinterpreted as clast-rich impact melt rocks or impact melt breccias. Four main types of impact melt glass are present, in contrast to previous studies that recognized only one type. These results are at odds with the current, generally accepted, definition of suevite. Given that the Ries is the original type occurrence of ‘suevite’, some redefinition of the term suevite may be in order. Furthermore, it is clear that sedimentary rocks, as well as crystalline rocks, were shock melted during the Ries impact event. The results of this study are, therefore, incompatible with previous models in which the zone of melting is restricted to the crystalline basement. It is apparent that impact melting in sedimentary targets is much more common than previously thought. Furthermore, there is no unequivocal evidence for the decomposition of carbonates or evaporites at any terrestrial impact site. Many previous assumptions about the response of sedimentary rocks during hypervelocity impact events are, therefore, incorrect. The products of impact into sedimentary targets may appear very different from those developed in crystalline targets. However, microscopic imaging and analysis suggests that these seemingly different lithologies may be genetically equivalent. Thus, the apparent ‘anomaly’ between the amount of impact melt rocks formed in sedimentary and crystalline targets may be due to a misinterpretation of the rock record.

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