the Zones” for Oxygenated Systems “Oxygen 220-160 100-50 Zone Zone One-Oxygen Ketone, 180-220 Formulas Aldehyde Alcohol One Two Two-Oxygen Acid 180-220 Formulas 160-180 One Aldehyde/Ketone 180-220 One And Alcohol Aldehyde/Ketone 180-220 Two And Ether Splitting in a coupled carbon NMR spectrum. C13 NMR’s are normally acquired as spectra, in which each carbon signal “decoupled” appears as a singlet, for reasons of speed and simplicity. However, at the cost of extra time and at the expense of some simplicity, it is also possible to get C13 NMR’s with splitting. The C-13 atoms are split by “coupled” directly attached hydrogens. These splitting values are very useful, and follow the N+1/N-1 rules (the number of lines is one greater than the number of attached H’s). Quartert (q) CH3 Triplet (t) CH2 Doublet (d) CH Singlet (s) C (no attached hydrogens) Coupled C-13 has at last two drawbacks: The signal to noise ratio and thus the sensitivity is a lot worse. Overlap: With coupled C-13 NMR, there are a lot more lines, and overlapping of lines becomes normal and confusing for non- simple molecules. Aromatics, Symmetry, Splitting. Most aromatics have symmetry, and both the number of aromatic lines and the splitting of the aromatic lines can be indicative of the substitution pattern on a benzene. Mono- and para-disubstituted benzenes have symmetry. 4 lines s, d, d, d Monosubstituted benzene. (Has symmetry) 4 s, s, d, d Para-disubstituted benzene. (Has symmetry) 6 lines s, s, d, d, d, d Ortho- or meta-disubstituted benzene. (Has no symmetry) Signal Height/Size Unlike 1H-NMR, where integration is really important, signal size is not very important in C-13 NMR.
the “Oxygen Zones” for Oxygenated Systems 220-160 Zone 100-50 Zone One-Oxygen Formulas Ketone, Aldehyde 180-220 Alcohol One Two Two-Oxygen Formulas Acid 180-220 160-180 One Aldehyde/Ketone And Alcohol 180-220 One Aldehyde/Ketone And Ether 180-220 Two Splitting in a coupled carbon NMR spectrum. C13 NMR’s are normally acquired as “decoupled” spectra, in which each carbon signal appears as a singlet, for reasons of speed and simplicity. However, at the cost of extra time and at the expense of some simplicity, it is also possible to get “coupled” C13 NMR’s with splitting. The C-13 atoms are split by directly attached hydrogens. These splitting values are very useful, and follow the N+1/N-1 rules (the number of lines is one greater than the number of attached H’s). Quartert (q) CH3 Triplet (t) CH2 Doublet (d) CH Singlet (s) C (no attached hydrogens) Coupled C-13 has at last two drawbacks: The signal to noise ratio and thus the sensitivity is a lot worse. Overlap: With coupled C-13 NMR, there are a lot more lines, and overlapping of lines becomes normal and confusing for non- simple molecules. Aromatics, Symmetry, Splitting. Most aromatics have symmetry, and both the number of aromatic lines and the splitting of the aromatic lines can be indicative of the substitution pattern on a benzene. Mono- and para-disubstituted benzenes have symmetry. 4 lines s, d, d, d Monosubstituted benzene. (Has symmetry) 4 s, s, d, d Para-disubstituted benzene. (Has symmetry) 6 lines s, s, d, d, d, d Ortho- or meta-disubstituted benzene. (Has no symmetry) Signal Height/Size Unlike 1H-NMR, where integration is really important, signal size is not very important in C-13 NMR.
Review%20of%20Organic%20Chem%20II.docx