Proton NMR study of molecular motion in solid cortisone

Polycrystalline cortisone (17,21-dihydroxy-4-pregnene-3,11,20-trione, C 21H 28O 5) has been investigated by proton NMR methods between 56 and 400 K at 14 and 25 MHz. Reductions in second moment and two very well-resolved minima in the spin-lattice relaxation time at both frequencies are attributed t...

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Bibliographic Details
Published inSolid state nuclear magnetic resonance Vol. 2; no. 5; pp. 261 - 264
Main Authors Andrew, E.R., Kempka, M.
Format Journal Article
LanguageEnglish
Published Netherlands Elsevier Inc 01.10.1993
Subjects
cortisone
Cortisone - chemistry
hormone
Magnetic Resonance Spectroscopy
methyl rotation
molecular dynamics
proton NMR
relaxation
cortisone
molecular dynamics
methyl rotation
proton NMR
relaxation
hormone
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Summary:Polycrystalline cortisone (17,21-dihydroxy-4-pregnene-3,11,20-trione, C 21H 28O 5) has been investigated by proton NMR methods between 56 and 400 K at 14 and 25 MHz. Reductions in second moment and two very well-resolved minima in the spin-lattice relaxation time at both frequencies are attributed to reorientation of the two methyl groups on carbons 18 and 19. The data are very well fitted over the entire temperature range to the Kubo-Tomita dipolar relaxation theory using the same parameters at both frequencies. Activation energies E a characterizing the hindrances to the two methyl reorientations were 5.9 and 15.5 kJ/mol, an unusually large difference. The relaxation constants were 6.4 and 7.9 × 10 8 s −2.
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ISSN:0926-2040
1527-3326
DOI:10.1016/0926-2040(93)90006-9