Inside the NMR Spectrometer

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