Download Integration and Splitting

Integration and Splitting
Integration
• Area under signal is proportional to the number
of protons in the set
• RELATIVE AREA is calculated by computer
Integration
Which proton
set is this?
• Trace of spectrum is cut into sections above
each signal to give integration values
Integration
• You need to “set” the values
• Here is a more realistic outcome
434.2
72.3
143.5
72.1
This is the NMR for a
C5H10O compound.
What are the
integration values?
Product Distribution by Integration
• In a mixture, areas are also proportional to
number of protons
• But they can by fractions
A
57%
B
D
B
C
E
F
43%
F
C
G
G
B F
D
E
A
Splitting
Splitting
• Shielding is also affected by magnetic fields
of nearby nuclei
N + 1 Rule
• The signal for protons b is a
quartet
• Signal b is “coupled” to the
three protons labeled “a”
• Four possible affects on signal b
• Summarized by this
simplification: n+1, where n =
number of adjacent,
nonequivalent protons
Splitting
Exchangeable protons
• If protons exchange, they are not coupled
• If protons are not coupled, they will no show
splitting in signal
• Typical for alcohols and acids
Label splitting for each proton set
N+1 is a Simplification
• We learn it first because it
applies to many molecules
• Assumes that all adjacent
protons couple to an identical,
measureable degree
• One exception: Aldehyde
• We will learn a more robust
treatment after we master
first principles
Very small coupling
between these protons,
even though they are
adjacent