Worksheet: NMR Splitting Patterns

In this worksheet, we will practice determining molecular structure from NMR splitting patterns and assigning multiplicities based on peak intensities.

Q1:

Which of the following correctly describes the relative intensities of splitting of an NMR peak?

  • AQuartet— 1 4 4 1
  • BTriplet— 1 3 1
  • CPentet— 1 3 5 3 1
  • DSextet— 1 5 1 0 1 0 5 1

Q2:

The splitting of energy levels in the presence of a magnetic field is caused by which of the following?

  • ASymmetry degeneracy
  • BPauli exclusion principle
  • CFermi contact interaction
  • DThe Zeeman effect
  • EBose-Einstein effect

Q3:

A 1 9 F NMR spectrum at room temperature reveals one well-defined peak. When cooled slightly, the peak becomes broadened. At N 2 ( 𝑙 ) temperatures, two well defined peaks are apparent. What is responsible for these observations?

  • AInteger quantum spin numbers ( 𝐼 = 1 , 2 , 3 , )
  • BSpin-spin coupling interactions
  • CFractional quantum spin numbers ( 𝐼 = 1 / 2 , 3 / 2 , 5 / 2 )
  • DDynamic fluxionality
  • ELow natural abundances of the 1 9 F nucleus

Q4:

What is the most likely cause of fluxional behavior in the NMR spectrum of F e ( C O ) 5 , iron pentacarbonyl?

  • ARotation of a hindered carbonyl bond
  • BDissociation and recoordination of the carbonyl ligands
  • COpening and closing of bridging carbonyls
  • DIsomerism between trigonal bipyramidal and square pyramidal configurations
  • EMonomer-dimer formation with a bridging carbonyl

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