Solution and Solid State Nuclear Magnetic Resonance Spectroscopic Characterization of Efavirenz

2016 
Abstract Samples of efavirenz (EFZ) were evaluated to investigate the influence of the micronization process on EFZ stability. A combination of X-ray diffraction, thermal analysis, FTIR, observations of isotropic chemical shifts of 1 H in distinct solvents, their temperature dependence and spin-lattice relaxation time constants (T 1 ), solution (1D and 2D) 13 C nuclear magnetic resonance (NMR), and solid-state 13 C NMR (CPMAS NMR) provides valuable structural information and structural elucidation of micronized EFZ and heptane-recrystallized polymorphs (EFZ/HEPT). This study revealed that the micronization process did not affect the EFZ crystalline structure. It was observed that the structure of EFZ/HEPT is in the same form as that obtained from ethyl acetate/hexane, as shown in the literature. A comparison of the solid-state NMR spectra revealed discrepancies regarding the assignments of some carbons published in the literature that have been resolved.
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