Electron paramagnetic resonance studies of molecular orientation and nuclear exchange in single crystals of morphine N-oxide.
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Authors
Weerts, Gary Lee
Subjects
Advisors
Tolles, W.M.
Date of Issue
1971-12
Date
Publisher
Monterey, California ; Naval Postgraduate School
Language
en_US
Abstract
Low temperature (-150°C) EPR spectra of the nitroxide generated
photolytically in a single crystal of N-nitromorpholine are complicated
by the presence of two magnetically distinct orientations of the N-0
bond within the crystal. As the temperature is raised, the spectra are
further complicated by motional effects. Since at -150° the molecule
is essentially frozen in the crystal lattice with respect to the time of
the EPR interaction, and since the nitrogen coupling tensor is markedly
anisotropic, the observed EPR spectrum varies widely as the orientation
of the applied field changes. The anisotropy of the nitrogen coupling
tensor made it possible to unequivocally determine the orientation of
the crystal with respect to the applied magnetic field. A series of
experimental spectra was then obtained for several combinations of
crystal orientation and temperature.In addition, computer programs
were developed which simulate low, intermediate, and high temperature
EPR spectra. By using a combination of experimental spectra and these
programs, it was possible to determine the angle between the two
orientations of the N-0 bond in the crystal and also to determine the
energy barrier to exchange.
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Approved for public release; distribution is unlimited.