Molecules that are brightly colored have a small energy gap between filled and empty electronic states (the HOMOLUMO gap; see Exercise 9.104). Suppose you have two samples, one is lycopene which is responsible for the red color in tomato, and the other is curcumin which is responsible for the yellow color in turmeric. Which one has the larger HOMO-LUMO gap?

Video transcript

Hi everyone here we have a question telling us that molecules that have small energy gaps between their H O. M. O and L. Um oh, orbital's appear brightly colored, And the question is which one of the following has a smaller H o M o. L U M. O. Energy gap, Congo red, which is a red dye or napped all yellow, a yellow dye. So we know that energy Equals one over wavelength. So the smaller the energy gap, the molecule will absorb a higher wavelength, so congo red appears red, so it will absorb the complimentary green. On the other hand, napped all yellow appears yellow so it will absorb the complementary violence. Green has a higher wavelength, then violet. So that means the energy gap is smaller, which makes our answer. Congo Red. Thank you for watching. Bye.