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

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Integration and Splitting

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  1. Integration and Splitting

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

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

  4. Integration • You need to “set” the values • Here is a more realistic outcome This is the NMR for a C5H10O compound. What are the integration values? 434.2 72.3 143.5 72.1

  5. Product Distribution by Integration • In a mixture, areas are also proportional to number of protons • But they can by fractions A D E 43% 57% B B F F C C G G F B A E D

  6. Splitting

  7. Splitting • Shielding is also affected by magnetic fields of nearby nuclei

  8. 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

  9. Splitting

  10. 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

  11. Label splitting for each proton set

  12. 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

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