Rules of the Day 2-2-09 1. Deuterium atoms do not show up in 1H-NMR spectra, so deuerated solvents are used to dissolve NMR samples. 3. The H atoms of relatively acidic functional groups (alcohols, carboxylic acids, amines) exchange rapidly , so they often do not split adjacent protons, and they can be replaced (signal disappears) with deuterium by adding a drop of D 2 O to the NMR sample. 4. H-bonding changes the location of a signal for H-bonding groups in a concentration dependent manner explaining why -OH and -NH 2 group signals can vary so much in location. 5. The splitting of a -CH 2- group adjacent to a chiral center will be "messed up" , that is split into many peaks. This is useful for identifying chiral centers in molecules. 6. 13C NMR tells you how many different types of carbon atoms are in a molecule. Because 13C atoms are so rare, you don't find two in the same molecule and there is no splitting (12C nuclei do NOT have spin quantum numbers of 1/2 so they do not split a 13C signal). Integration
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