NMR spectroscopy

• What is NMR spectroscopy used for?

  It is used to determine the structure of a molecule.
• How does NMR spectroscopy analyze bond environments?

  It analyzes the energy absorbed by different bond environments.
• What does each peak in an NMR spectrum represent?

  Each peak represents a different bond environment within the molecule.
• What is the standard molecule used in NMR spectroscopy?

  Tetramethylsilane (TMS) is the standard molecule.

  
• Why is TMS considered a standard molecule in NMR?

  It contains four identical carbon and hydrogen environments.
• At what value does TMS appear on the NMR spectrum?

  TMS appears at ∂=0 ppm on the x-axis.
• What does C¹³ NMR analyze?

  C¹³ NMR analyzes the different carbon environments in a molecule.
• How do carbon environments near oxygen behave in C¹³ NMR?

  They have ∂ values that are shifted to the right.
• Why might a molecule with symmetry display fewer ∂ peaks than carbon atoms?

  Symmetry can cause multiple carbon atoms to have the same environment.
• How many carbon atoms does 1,2-cyclohexanediol contain?

  It contains six carbon atoms.
• How many peaks does the NMR spectrum of 1,2-cyclohexanediol show?

  It shows three peaks due to the symmetry of the molecule.

  
• What does H¹ NMR analyze?

  H¹ NMR analyzes the different hydrogen environments in a molecule.
• What must samples be dissolved in for H¹ NMR analysis?

  They must be dissolved in a non-hydrogen-containing solvent.
• What is a common solvent used in H¹ NMR?

  CCl₄ is a common solvent used.
• Why are H¹ NMR spectra more complex than C¹³ spectra?

  Because the heights of the peaks show the relative intensity of each ∂ value.

  
• What do the heights of the peaks in H¹ NMR correspond to?

  They correspond to the number of hydrogens in that certain environment.
• What does the splitting pattern in H¹ NMR indicate?

  It indicates how many hydrogens are on the adjacent carbon atom.

  
• What is the 'n+1' rule in NMR spectroscopy?

  The 'n+1' rule states that n is the number of hydrogens on the adjacent carbon.
• What does a singlet indicate in H¹ NMR?

  A singlet indicates no hydrogens on the adjacent carbon.

  
• What does a doublet indicate in H¹ NMR?

  A doublet indicates one hydrogen on the adjacent carbon.

  
• What does a triplet indicate in H¹ NMR?

  A triplet indicates two hydrogens on the adjacent carbon.

  
• What does a quartet indicate in H¹ NMR?

  A quartet indicates three hydrogens on the adjacent carbon.

  
• What is a common splitting pattern in H¹ NMR?

  A triplet-quartet splitting pattern is a common combination.

  
• What does the triplet-quartet splitting pattern represent?

  It represents a -CH₂-CH₃ fragment.

  
• How can multiple fragments be used in NMR spectroscopy?

  • They can be pieced together to determine the full molecule structure.
  • Each fragment corresponds to a specific splitting pattern.