This dissertation focuses on the use of theoretical tools to analyze wavefunctions and thus elucidate chemical phenomena. Our investigation of weak bonds shows them to be more prevalent than was previously believed. We find two types of weak bonds, associated with delocalized or with steric interactions, and we classify weak bonds by their topological properties in a way that correlates well with the origin of the bonding interactions. We develop a quantitative measure of bonding. The covalent bond order based on a partitioning of the total number of electrons in a system is shown to be remarkably consistent with the expectations of "chemical intuition" without building in prejudices due to arbitrary references to basis sets. / In applications of these tools, we interpret the results of electronic structure calculations on trifluoro-, tricyano-, and trinitromethanes and their deprotonated analogs. We demonstrate that, most probably as a result of changes in geometries upon deprotonation, there is no single-parameter correlation between the absolute gas-phase acidities and a number of geometric, topological, and charge indices for these molecules. We also elucidate bonding patterns in various rotamers of the "push-pull" hexasubstituted ethanes, C(NH$\sb3)\sb3$CX$\sb3$, (X = F, CN, or NO$\sb2$). We show that bonds in these systems can be classified as ionic or covalent on the basis of GAPT charges and charge transfers, as well as by Bader charges and topological properties of the electron density at bond critical points. These large-scale calculations demonstrate that it is now feasible to compute wavefunctions and to perform fruitful analyses of them for many large systems of chemical interest. This research yields a number of unusual results, including the fact that C(NH$\sb2)\sb3$C(CN)$\sb3$ is the first molecule known to possess in vacuo two stable isomers that have the same formal connectivities between atoms, but different electronic structures: one covalent and the other ionic. / Source: Dissertation Abstracts International, Volume: 52-03, Section: B, page: 1464. / Major Professor: Jerzy Cioslowski. / Thesis (Ph.D.)--The Florida State University, 1991.
| Identifer | oai:union.ndltd.org:fsu.edu/oai:fsu.digital.flvc.org:fsu_76377 |
| Contributors | Mixon, Stacey Tyrone., Florida State University |
| Source Sets | Florida State University |
| Language | English |
| Detected Language | English |
| Type | Text |
| Format | 125 p. |
| Rights | On campus use only. |
| Relation | Dissertation Abstracts International |
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