High-Resolution Carbon-13 Nuclear Magnetic Resonance Spectra of Solid D-Camphor

Abstract

Proton decoupled natural abundance carbon-13 nmr spectra of solid polycrystalline d-camphor have been measured between 275K and 343K. The observed line widths are relatively sharp, making it possible to measure ¹³C chemical shifts and spin-lattice relaxation times, T₁'s, for several of the individual carbon resonances. From the temperature dependence of T₁ an activation energy of 14.2 ± 2 kJ mole⁻¹ is calculated. Effective rotational correlation times derived from the ¹³C T₁'S are compared with those obtained for d-camphor using dielectric techniques. Some general advantages of proton decoupled ¹³C nmr over ¹H nmr in studying molecular reorientation in orientationally disordered solids are discussed.