London forces between benzene molecules

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Discussion Overview

The discussion centers around the interactions between benzene molecules via London forces, exploring the strength and nature of these interactions in comparison to other compounds. Participants delve into theoretical aspects, potential applications, and the implications of these forces in molecular stacking and polymer formation.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions how easily benzene molecules interact via London forces, suggesting that the large surface area and pi-orbitals may enhance these interactions.
  • Another participant asserts that benzene does interact through London forces, emphasizing the importance of dispersion forces in understanding its physical properties.
  • A participant seeks clarification on the strength of benzene's interactions relative to other compounds, expressing curiosity about the properties of a hypothetical polymer made from benzene rings.
  • One participant compares the binding energy of benzene dimers due to London forces to that of hydrogen bonds, indicating that London forces are relatively weak.
  • Another participant speculates that a polymer of benzene rings could exhibit properties of a low-temperature thermotropic liquid crystal.
  • A participant discusses the role of hydrogen atoms in benzene and mentions their involvement in electrophilic aromatic substitution, while also referencing metalocene compounds.
  • One participant notes that the quantitative nature of London interactions depends on the electronic structure of the molecules and suggests using potential energy models to study these interactions.

Areas of Agreement / Disagreement

Participants generally agree that benzene interacts via London forces, but there is no consensus on the strength of these interactions relative to other forces, such as hydrogen bonding. The discussion includes multiple viewpoints on the implications of these interactions and the potential for polymer formation.

Contextual Notes

Participants express uncertainty regarding the relative strength of London forces compared to other intermolecular forces and the specific conditions under which these interactions occur. There are also unresolved questions about the properties of hypothetical polymers made from benzene.

Who May Find This Useful

This discussion may be of interest to those studying molecular interactions, organic chemistry, and materials science, particularly in the context of aromatic compounds and their applications.

espen180
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How easily do benzene molecules interact with london forces?

I imagine that the relatively large surface area of the aromatic ring coupled with the pi-ring, which is a pretty large orbital makes london forces of a pretty large magnitude possible, but I am not certain.

Does anyone have any insight into this?

Thanks in advance.
 
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Well, I'm not sure what kind of answer you expect to 'how easily'... They do certainly interact via london forces, just like everything else.

Being nonpolar (and as you said, pi-conjugated) molecules, they certainly do interact, forming nice little stacks (cutely named pi-stacks!)
I guess you could put it this way: You can't get an very useful description of the physical chemical properties of benzene without taking into account dispersion forces.

And since I happen to have a relevant paper right here on my desk, here are some facts and figures:
A benzene dimer with two benzenes stacked directly on top of each other has a binding energy (due to London forces) of -1.8 kcal/mol at optimal distance, which is 3.70 Å.
 
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Thank you for your answer. I guess the wording "How easily..." was flawed. What I had in mind was information about how stongly they interact relative to other compunds.

I found the figures you supplied to be quite ammusing, as I immagine a polymer of suck rings. I wonder what properties such a polymer would have?
 
espen180 said:
I found the figures you supplied to be quite ammusing, as I immagine a polymer of suck rings. I wonder what properties such a polymer would have?

Well, it's not a very strong force keeping it together really.
For comparison (which I should've given earlier), a single hydrogen bond is typically ~5 kcal/mol.

I doubt you could make a really big stack, given the low energy involved, the forces of entropy would overcome it pretty quickly.
 
It would have the property of a very low temperature thermotropic liquid crystal, very likely of the http://en.wikipedia.org/wiki/Liquid_crystal" type.
 
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The Hydrogen atoms in Benzene molecule are inactiv and usualy they are involved only in Electrophylic aromatic substitution mechanism. But uper or down Benzene ring electrons act all together and make some Mettalocenes sandwich aromatic compounds as
Chromocene Cr(CH6)2.
 
The interaction between molecules related to London forces is weak. But, the quantitative London interaction depends on the electronic structure of the molecules involved, i.e., for the simpler case, London forces depend on the ionization energy of the atoms.

To study these interactions one should introduce a potential energy model like the simple point charge model or any of its modifications.

Interesting question.
 

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