Diels-Alder Reaction: A Simple Explanation?

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SUMMARY

The discussion centers on the Diels-Alder reaction, specifically critiquing a professor's electrostatic explanation while neglecting molecular orbital theory. Key points include the assertion that nucleophiles attack electrophiles and that electrons in HOMOs transition to LUMOs. The critique highlights inconsistencies in the professor's explanation regarding the physical state of ethene and the role of stereoselectivity in Diels-Alder reactions. The conclusion emphasizes the necessity of considering orbital symmetries for a comprehensive understanding of the reaction mechanism.

PREREQUISITES
  • Understanding of Diels-Alder reaction mechanisms
  • Familiarity with nucleophiles and electrophiles
  • Knowledge of HOMO-LUMO theory
  • Concepts of stereoselectivity in organic chemistry
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  • Research the role of orbital symmetries in Diels-Alder reactions
  • Study the impact of molecular orbitals on reaction mechanisms
  • Explore stereoselectivity in various organic reactions
  • Investigate the physical properties of ethene and its implications in reaction dynamics
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Chemistry students, organic chemists, and educators seeking to deepen their understanding of the Diels-Alder reaction and its underlying principles.

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Homework Statement



This is my prof's explanation of Diels-Alder ... below is the mechanism and some resonance structures he drew to explain the concerted movement of electrons to the class ...

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Homework Equations



Nucleophiles attack electrophiles.

Electrons in HOMOs go into LUMOs.

The Attempt at a Solution


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So my professor's explanation is very interesting for a few reasons:

1) He completely sidesteps all the ramblings about molecular orbitals in the text.

2) His electrostatic explanation is very tempting based on Occam's razor alone but ethene is a gas at STP. If the dipolar resonance structure were a big contributor then wouldn't ethene instead be a liquid?

3) The book has a section on stereoselectivity and Diels-Alder reactions. How can pure electrostatics explain stereoselectivity?

So am I crazy or what for thinking that the guy's electrostatic explanation sounds like a story of unicorns in the park?
 
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Qube said:
unicorns in the park?
Are you certain he wasn't discussing "orbital symmetries" with his plus and minus signs?
 
Bystander said:
Are you certain he wasn't discussing "orbital symmetries" with his plus and minus signs?

Yes I'm sure he didn't mention orbitals at all.
 

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