Integration and Splitting

Integration Area under signal is proportional to the number of protons in the set RELATIVE AREA is calculated by computer

Integration Trace of spectrum is cut into sections above each signal to give integration values Which proton set is this?

Integration You need to “set” the values Here is a more realistic outcome This is the NMR for a C 5 H 10 O 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 BB C DE F G F D E C G A B F 57% 43%

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