Worksheet: Functional Groups in UV–Vis Spectra

In this worksheet, we will practice identifying functional groups in a compound by assessing the shapes and positions of peaks in UV–Vis spectra.

Q1:

The method of continuous variations, also known as Job’s method, uses the intersection of the ligand-line and the metal-line to determine which of the following?

  • AThe maximum intensity of source photons transmitted.
  • BThe concentration at which the detector can no longer respond to the signal.
  • CThe number of dimeric molecules formed.
  • DThe mole ratio between the metal and ligand in a complex.
  • EThe oxidation number of the metal.

Q2:

Which of the following would result in a hypsochromic shift in the UV spectra?

  • ACyclization of an aliphatic compound
  • BDehydration of an alcohol to form a double bond
  • CAddition of an amino group
  • DSaturation of a double bond

Q3:

What does increasing conjugation in a series of analogous compounds results in?

  • AHyperchromic effect
  • BHypsochromic shift
  • CHypochromic effect
  • DBathochromic shift

Q4:

Why does increased conjugation cause a shift to higher wavelengths?

  • AIt causes the vibrational and rotational levels of the molecules to become excited.
  • BIt increases the distance ( Δ 𝐸 ) between the HOMO and LUMO levels.
  • CIt changes the types of electronic transitions available from 𝜋 𝜋 - to 𝑛 𝜋 -
  • DIt decreases the distance ( Δ 𝐸 ) between the HOMO and LUMO levels.

Q5:

Which of the following is true of the Woodward-Fieser Rules for conjugated carbonyl compounds?

  • AOnly include substitutes directly adjacent to the carbonyl group
  • BAre the same as the rules for dienes
  • CCan also be applied to benzene derivatives
  • DInclude a solvent correction value

Q6:

In general, when calculating empirical values for 𝜆 m a x , what is the result of adding a substituent group?

  • AA hyperchromic effect
  • BA hypsochromic shift
  • CA hypochromic effect
  • DA bathochromic shift

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