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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