http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
Conformational analysis of some small non-rigid molecules
xviii, 184 leaves : illustrations ; 29 cm
Low frequency infrared and Raman spectra of gas-phase molecules can be used to obtain vibrational data for large amplitude vibrations which are important for understanding molecular conformations. Subsequently, this data can be fit to appropriate potential energy surfaces which are functions of internal vibrational coordinates. In this work, a variety of vibrational potential energy surfaces and the quantum mechanical calculations associated with these have been considered. Vectorial methods for calculating the kinetic energy functions for asymmetric five-membered rings, each with a single unsaturation, have been developed. These methods provide kinetic energy expansions which are functions of the ring-puckering coordinate for each molecule. The ring-puckering vibrational data for silacyclopent-2-ene-1,1-d2 was recorded and used together with similar data for the undeuterated species to determine a single minimum one - dimensional potential energy function. The observed mid-infrared combination band spectra resulting from the internal rotation vibrations of cyclopropylsilane-d3 and cyclopropylgermane were fit to periodic potential energy functions. The two-dimensional ring-puckering potential energy functions of two spiro compounds, 4-silaspiro-(3 , 3)-heptane (SSH) and 3 - cyclopentenespiro - 3 ' - cyclopentene, were estimated from the single ring molecules. In addition, an interaction term of the form cx^2y^2 was included for each molecule. The parameter c reflects the magnitude of the coupling between the two ring puckering potential energy functions. Calculations were carried out in order to examine the characteristics of the potential surfaces, the energy levels and the wave functions of the spiro compounds as a function of the constant c. Two computer programs were written and used to calculate and graphically present the wavefunctions associated with the energy states of one- and two-dimensional potential energy functions An experimental apparatus based on an Nd:YAG laser was built to study the large amplitude vibrations of molecules in electronically excited states.