Inside the NMR Spectrometer
a) Normal nucleib) Nuclei in a magnetic field
Radio waves will ‘pulse’ these nuclei to stimulate a response that can be recorded
The nuclei’s response to the ‘pulse’ is then recorded as a peak (or set of peaks) which will be placed on a graph (see above).
These peaks are always reference to TMS (tetramethylsilane = 0 ppm)
Where the peaks occur depends on the shielding or deshielding effects experience by that nuclei.
Approximate ppm of certain H’s(Note: Additional deshielding can change these values)
Very deshielded
Very Shielded
Note: Remember these values will change if there is additional deshielding effects.
N + 1 Rule
N + 1 = 1 peak
N + 1 = 2
N + 1 = 3
N + 1 = 4
N + 1 = 5
N + 1 = 6
N =
Example #1
Example #2 – Integration
2 cm
6 cm
2/2 = 1 equiv H’s1 x 3 = 3 H’s
6/2 = 3 equiv H’s3 x 3 = 9 H’s
-Divide by 2, because it is the lowest out of all the distances-You may need to multiply by some whole number until you reach the appropriate amounts of H’s (Fudge Factor).
We can also use 13C NMR
*Approximate range (ppm) of different carbons
Time = 5 minutes of scanning
Time = 1 hour of scanning (or more)
# of Unsaturations =
#C - #H/2 - #Hal/2 + #N/2 +1
C = CarbonH = HydrogenHal = HalogensN = Nitrogen
Be sure to follow this example in the workshop!
Pieces of the Puzzle
J Value Examples