NMR

NMR

1. Carbon 13 NMR gives you information about how many carbons there are and the environments they are in

2. Proton NMR gives you information of number of hydrogen atoms and the environments they are in

3. Tetramethylilane is used as a standard

4. Carbon 13 NMR

   • 1) Count number of carbon environments
     • Each peak represents a different environment
   • 2) Look up the chemical shifts in the formula booklet and match the peaks with them
   • 3) Try out possible structures

5. Proton NMR

   • In H NMR the relative area under each peak tells you how many hydrogens are in each environment
   • Spin-spin coupling splits the peaks
     • The split peaks are called multiplets and they split to one more than the number of hydrogens on neighbouring environment - n+1 rule
     • Doublet - split into two (one H on neighbouring environments)
     • Triplet - split into three (two H on neighbouring environments)
     • Quartet - split into four (three H on neighbouring environment)
   • You need to use a solvent that doesnt contain protons so hydrogen nuclei are replaced by deuterium
   • Chemical shift due to OH or NH is very variable (large range)
     • Run two spectra, one with deuterium oxide added
     • If an OH or NH is present it will swap with deuterium and will disappear

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