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 .

  • Athe maximum intensity of source photons transmitted
  • Bthe oxidation number of the metal
  • Cthe concentration at which the detector can no longer respond to the signal
  • Dthe mole ratio between the metal and ligand in a complex
  • Ethe number of dimeric molecules formed

Q2:

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

  • ADehydration of an alcohol to form a double bond
  • BAddition of an amino group
  • CSaturation of a double bond
  • DCyclization of an aliphatic compound

Q3:

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

  • AHypochromic effect
  • BBathochromic shift
  • CHyperchromic effect
  • DHypsochromic shift

Q4:

Why does increased conjugation cause a shift to higher wavelengths?

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

Q5:

Which of the following is true of the Woodward–Fieser rules for conjugated carbonyl compounds?

  • AThey can also be applied to benzene derivatives.
  • BThey only include substitutes directly adjacent to the carbonyl group.
  • CThey are the same as the rules for dienes.
  • DThey include a solvent correction value.

Q6:

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

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

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