Unusual asymmetry of methyl /sup 2/H EFG in thymine: a solid state deuterium NMR and ab initio MO study

Journal Article · Wed Apr 15 00:00:00 EDT 1987 · J. Am. Chem. Soc.; (United States)

DOI:https://doi.org/10.1021/ja00242a054· OSTI ID:6631340

Hiyama, Y; Roy, S; Guo, K; Butler, L G; Torchia, D A

Solid-state /sup 2/H NMR spectroscopy is a powerful method of studying molecular motion in the solid state. The power of this technique derives from the facts that quadrupole coupling is the dominant interaction and the electric field gradient (EFG) tensor is usually axially symmetric for a deuteron bonded to carbon, with the unique axis along the C-D bond. In the case of a methyl group, rapid 3-fold rotation yields an averaged EFG whose symmetry axis is along the rotation axis, and the corresponding powder pattern is axially symmetric (eta less than or equal to 0.01) with a quadrupole splitting of ca. 40 kHz. They are interested in obtaining spectra of thymidine and ribothymidine, deuteriated at the methyl positions, to study motion of nucleotide bases in DNA and tRNA, respectively. In their initial work they are studying the dynamics of the model compound, thymine-methyl-d/sub 3/. Inversion-recovery /sup 2/H NMR spectra of this compound clearly showed the T/sub 1/ anisotropy predicted for 3-fold methyl jumps. The linear Arrhenius plot of correlation time, tau/sub c/, against 1/T (where tau/sub c/ = tau/sub 0/ exp(E/RT)) yielded an apparent activation energy of 6.9 kJ/mol and a preexponential factor, tau/sub 0/, of 2 x 10/sup -13/ s. These results show that the /sup 2/H spin-lattice relaxation is determined by the 3-fold methyl motion. However, this motion does not account for the asymmetry in the observed line shape.

• Research Organization: National Institutes of Health, Bethesda, MD
• OSTI ID: 6631340
• Journal Information: J. Am. Chem. Soc.; (United States), Journal Name: J. Am. Chem. Soc.; (United States) Vol. 109:8; ISSN JACSA
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
ACTIVATION ENERGY
ARRHENIUS EQUATION
AZINES
DATA
DEUTERIUM
ENERGY
EQUATIONS
EXPERIMENTAL DATA
HETEROCYCLIC COMPOUNDS
HYDROGEN ISOTOPES
HYDROXY COMPOUNDS
INFORMATION
ISOTOPES
LIGHT NUCLEI
MAGNETIC RESONANCE
MOLECULAR ORBITAL METHOD
MOLECULAR STRUCTURE
NMR SPECTRA
NUCLEAR MAGNETIC RESONANCE
NUCLEI
NUMERICAL DATA
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PYRIMIDINES
RESONANCE
SPECTRA
STABLE ISOTOPES
THYMINE
URACILS