Crash course in applied NMR

1
Crash course in applied NMR
2
Practical aspects

• Sample preparation
• No solids!
• Balanced tubes, proper filling
• Choice of solvents, deuterium locking
• Tube handling and cleaning
• Tube labeling
• There is an on-line manual for our NMR!

3
Instrument etiquette

• Indicate when machine is in use
• Return everything as you found it
• No metals around NMR
• Leave door closed (and AC in control)
• Consider sample concentration, no endless runs
  during day time

4
Basic considerations

• CV vs. FT principles
• Locking, shimming
• Definitions pulse, pulse delay
• Signal to noise ratio
• Proton vs. carbon
• Sample spinning
• Spinning side bands
• TMS outdated chloroform signal at 7.26

5
A second look at interpretation

• Kinetic effects DMF has two methyl peaks!
• Methylcyclohexane (below)
• same shift for axial/equ. methyl

6
Exchangeable protons

• Types amines, alcohols, carboxylic acids
• Pooling of different types
• Peak broadening, see below
• Shaking out with D2O
• Absence of spin splitting

4-hydroxybenzoic acid
7
Second order considerations

• Conditions for 2nd order
• Leaning peaks, uninterpretable spectra

benzofuran
8
Description of spin systems

• J values
• 1, 2, and 3 bond coupling
• Long range coupling
• Spin systems A-B, A-X etc.

9
Aromatic patterns phenyl
benzoic acid
toluene
10
Aromatic patterns disubstitution
3-nitobenzoic acid
4-hydroxybenzoic acid, AAXX
11
Ortho, multiple subst.
12
Lanthanide shift reagents
Addition of paramagnetic compounds such as
Eu(fod)3
13
Suggested review

• McMurry, discussion of homotopic, heterotopic,
  enantiotopic, and diastereotopic relationships
• Hoffman Ch. 11