In 13C[1H] NMR spectra of liquids, one observes a single resonance for each symmetrically nonequivalent carbon atom. The same is true of the 13C CPMAS spectra of solids. The difference is that the molecular symmetry is the determining factor in liquids NMR whereas the crystallographic symmetry is the determining factor in solids NMR. As a result, solids NMR can give different spectra for different solid polymorphs and multiple resonances due to multiple nonequivalent molecules in the asymmetric unit of the crystal structure. The figure below compares the solids 13C CPMAS and liquids 13C[1H] NMR spectra of a vitamin C (ascorbic acid) tablet.
The structure is provided in the figure and the assignment for all of the carbon atoms is color coded. In the liquids spectrum, one observes resonances for each carbon in the molecule. In the 13C CPMAS spectrum, one observes that three of the six 13C resonances are doubled. This doubling is consistent with there being two nonequivalent ascorbic acid molecules in the asymmetric unit of the crystal. Presumably, the other three resonance are doubled as well but there is insufficient resolution in the spectrum for this observation. The broad features in the spectrum are due to additives in the vitamin C tablet which include, hypromellose, stearic acid and carnauba wax.
Hybrid polarizing solids for pure hyperpolarized liquids through dissolution dynamic nuclear polarization
From The DNP-NMR Blog:
Hybrid polarizing solids for pure hyperpolarized liquids through dissolution dynamic nuclear polarization
Gajan, D., et al., Hybrid polarizing solids for pure hyperpolarized liquids through dissolution dynamic nuclear polarization. Proc. Nat. Aca. Sci. USA, 2014. 111(41): p. 14693-14697.
http://www.pnas.org/content/111/41/14693.abstract
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Metabolic profiling of vitamin C deficiency in Guloâ??/â?? mice using proton NMR spectroscopy
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Abstract Nutrient deficiencies are an ongoing problem in many populations and ascorbic acid is a key vitamin whose mild or acute absence leads to a number of conditions including the famously debilitating scurvy. As such, the biochemical effects of ascorbate deficiency merit ongoing scrutiny, and the Gulo knockout mouse provides a useful model for the metabolomic examination of vitamin C deficiency. Like humans, these animals are incapable of synthesizing ascorbic acid but with dietary...
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03-03-2011 02:06 AM
Post-Doc fellowship in NMR Methods to Study Ionic Solids/liquids - Univ. of Aveiro/Lisbon (Portugal)
Post-Doc fellowship in NMR Methods to Study Ionic Solids/liquids - Univ. of Aveiro/Lisbon (Portugal)
A 1-year postdoctoral position is available starting from January 2011, (extendable for additional 12 months) to study the “solid structure” of ionic liquids (ILs) and ionic solids (ISs) with relevance to the pharmaceutical industry. The research will be centred in the use of NMR techniques in tandem with molecular modelling to study the physical chemistry of molecular interactions in ILs and ISs. The project will be performed at the NMR centres at the Universities of Aveiro (solid state...
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Invest Ophthalmol Vis Sci. 2003 May;44(5):2047-58
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[NMR paper] Characterization of the EGF-like module pair 3-4 from vitamin K-dependent protein S u
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13C NMR of Vitamin C - Solids vs. Liquids NMR
Linear Mode
