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Author Topic: fluorescence  (Read 188 times)

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ostudent

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fluorescence
« on: January 13, 2019, 07:41:33 PM »

See attachment for problem.

In this question, I am confused about the effect of rigidity on effects of UV radiation.
I agree that C is the answer because it is the most highly conjugated. However, why does C being "the most rigid due to its fused aromatic ring system" make it more likely to have intense yellow fluorescence. Can this be explained?
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Irlanur

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Re: fluorescence
« Reply #1 on: January 13, 2019, 09:25:26 PM »

The argument is a bit hand-waving, but one can argue than in order to be fluoresecent, the light energy that was taken up also has to be released via a radiative process. If a molecule has a lot of vibrational degrees of freedom, i.e. if it can wiggle a lot, most energy will be released as heat, not as visible light.
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rolnor

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Re: fluorescence
« Reply #2 on: Yesterday at 02:40:46 AM »

I think A and B have to little conjugation to be fluorescent?
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