I. Study of molecular orbital degeneracy in C5H5. II. The crystal and molecular structure of cyclopentadiene

Citation

Liebling, Gerald R. (1965) I. Study of molecular orbital degeneracy in C5H5. II. The crystal and molecular structure of cyclopentadiene. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/KEZ8-7539. https://resolver.caltech.edu/CaltechETD:etd-09302002-122910

Abstract

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Part I. The paramagnetic resonance of the cyclopentadienyl radical C5H5 has been observed in a single oriented crystal of cyclopentadiene at temperatures ranging from 25[degrees]K to 150[degrees]K. The spectra are of two types, high-temperature and low-temperature spectra, with the transition occurring reversibly between 70[degrees]K and 120[degrees]K. The high temperature spectra consist of six equally spaced lines with a splitting of 6.2 gauss and can be accounted for in terms of a uniform spin distribution around the ring and rapid reorientation of the ring in its plane. The low-temperature spectra are slightly anisotropic and can be reasonably well accounted for by a distorted C5H5 radical with a nonuniform spin distribution undergoing rapid reorientation in its molecular plane.

Part II. The crystal structure of cyclopentadiene, C5H6, has been determined from X-ray diffraction photographs made at about -150[degrees]C. The crystals are monoclinic, space group P2[subscript 1]/n, with cell dimensions [...]. Intensities of 70 reflections recorded on four zero-level precession photographs were estimated visually and used in a least-squares refinement of the atomic coordinates. The final R factor for these reflections is 0.10.

The five-membered ring of carbon atoms is planar; the values for the bond distances are in close agreement with those previously determined by electron diffraction techniques.

ABSTRACTS OF PROPOSITIONS

Proposition 1: A method of constructing semiconductor devices that would operate at very low temperatures is proposed.

Proposition 2: It is proposed that the EPR spectra of x-irradiated trimesic acid be studied for the possibility of observing an aromatic sigma radical.

Proposition 3: Several experiments are proposed that would elucidate the mechanism of carbene addition across a double bond.

Proposition 4: It is proposed that attenuated total reflection spectroscopy can be very useful for studying electrode processes in electrochemical reactions.

Proposition 5: Several EPR experiments are proposed.

Thesis Files