Give a molecular structure-based explanation for the differences in the UV-Vis spectra in I and II. Use detailed MO schemes for A and B for illustration. (12 marks)

Methyl red protonation

Does the double bond of N=N, C=O and lone pair of oxygen and nitrogen involved in the MO diagram?

  • 4
    $\begingroup$ The longer the conjugated pi-system, the longer the absorbed wavelength. In the form A, there is a huge conjugated pi system . It is probably II. In the form B, there are two separate conjugated pi system. it corresponds probably to I. $\endgroup$
    – Maurice
    Dec 17, 2020 at 16:51
  • 2
    $\begingroup$ I am able to assign A and B to the their specta, however I am not sure on how to draw detailed MO schemes for A and B in order to show the electron transitions. $\endgroup$
    – sara
    Dec 17, 2020 at 16:54


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