Linked Questions

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0 answers
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Extended resonance and colour [duplicate]

I was pretty sure that this would've been asked before but I couldn't find anything here. I've noticed that system with multiple benzene rings and pi donating/accepting groups tend to be quite ...
Gaurav Sai Maddipati's user avatar
9 votes
1 answer
3k views

How does conjugation affect reactivity?

From this topic on MOs of butadiene vs ethene, it is clear that when two ethene molecules are combined to extend the conjugate chain, the HOMO is raised in energy and the LUMO is lowered in energy. ...
Adroit's user avatar
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6 votes
2 answers
16k views

Why does tryptophan absorb UV light?

Why is that tyrosine, phenyalanine, and tryptophan absorb UV light while other amino acids don't even absorb visible light? Does it have something to do with aromatocity?
Physicsapproval's user avatar
1 vote
1 answer
1k views

Simple way to understand why chromophores often have double bonds?

Chromophores — atoms or groups of atoms within a molecule that absorb some visible wavelengths better than others — result in compounds that have color. For example, see this answer about azo dyes, ...
uhoh's user avatar
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5 votes
1 answer
4k views

Why does mesitylene absorb at a longer wavelength than benzene (UV-Vis)?

According to UV-Vis spectroscopy, mesitylene (1,3,5-trimethylbenzene) absorbs at $\lambda_\text{max} = 210\ \mathrm{nm}$ while benzene absorbs at the slightly shorter wavelength of $\lambda_\text{max} ...
Nova's user avatar
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0 votes
0 answers
139 views

Behavior of π-conjugated chromophores in the presence of light

In the presence of light, I have read that, structures comprising π conjugated systems like retinol, straighten out from their curled positions, what phenomenon drives this behavior and why does this ...
Ghosal_C's user avatar
  • 501
10 votes
3 answers
5k views

Why is diene more reactive than alkene?

The chemical reduction of 1,3-butadiene with sodium in alcohol gives mainly the 1,4-addition product that is but-2-ene. Under these condition the isolated double bond are not reduced. This suggest ...
pcforgeek's user avatar
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1 vote
1 answer
683 views

Relation between number of conjugated double bonds and absorbance? [duplicate]

I observed the absorbance on Phenolphthalein in acidic and basic medium, and I know that the absorbances differ due to the number of conjugated double bonds, but I am not sure exactly why this happens....
Sreekar Voleti's user avatar
0 votes
2 answers
1k views

How are electrons in conjugated molecules excited? [duplicate]

I have recently started reading about colour in organic molecules and come across conjugation of pi bonds. My question is pretty short... In transition metal ions I understand colour is caused by ...
MY2K's user avatar
  • 359
11 votes
2 answers
5k views

The energy gap between a pi-conjugated system with (2 bonding and 1 anti-bonding orbital) and (1 bonding and 2 anti-bonding) orbitals

I asked a question previously about "why" it is the case the expanding the size of pi-conjugated systems decreases the required energy to excite an electron from a HOMO to a LUMO band: Why does the ...
user4717's user avatar
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