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20 Cards in this Set
- Front
- Back
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Carbon-13 NMR spectroscopy:
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gives us evidence about the connectivity and environment of carbon atoms in a molecule.
- can help us confirm the structure of a molecule for which we already have some structural information, or it can give us evidence that can help us elucidate the structure of an entirely unknown compound. |
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one signal for each unique carbon:
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each carbon atom that occupies a unique environment in a molecule produces one signal in a carbon-13 spectrum. Carbon atoms that are equivalent by molecular symmetry also produce one signal.
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what influences the chemical shift/ signals in NMR spectra?
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differences in electron density.
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Chart of carbon-13 NMR chemical shifts:
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C-13 NMR shift range of
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10-25
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C-13 NMR shift range of
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20-50
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C-13 NMR shift range of
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25-60
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C-13 NMR shift range of
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30-40
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C-13 NMR shift range of
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40-90
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C-13 NMR shift range of
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20-70
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C-13 NMR shift range of
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20-90
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C-13 NMR shift range of
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70-90
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C-13 NMR shift range of
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110-150
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C-13 NMR shift range of
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120-150
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C-13 NMR shift range of
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110-125
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C-13 NMR shift range of
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150-170
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C-13 NMR shift range of
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155- <180
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C-13 NMR shift range of
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>160 - <190
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C-13 NMR shift range of
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190-220
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Using C-13 NMR:
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1. count # of signals
---- indicate # of C occupying unique environments in molecule 2. compare chemical shifts w/ chart may show "type" of C. 3. considering pts. 1 & 2.... propose structure. |
