solvent that repels itself

[chiddler]

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What is an example of a solvent whose component molecules repel each other? As opposed to water molecules that attract each other.

a tbr passage suggests that this is possible.

 

[Dasypus]

Maybe benzene? Benzene molecules really don't want anything to do with each other. Or CCl4. I'm not sure which is less prone to induced dipoles, but for each, the only intermolecular forces are London dispersion.

 

[dmf2682]

Well, natural gas like methane wouldn't repel per se just not attract. Plus it would be impractically cold. To actively repel you'd need to have symmetric, charged molecules.

 

[MedPR]

Wouldn't methane molecules still have london dispersion forces between them? Aren't those attractive forces?

 

[chiddler]

any solvent that has any sort of liquid form has attractive forces! i guess my question doesn't make sense :-x

the passage says that "strong attractive forces" is one extreme, and the other extreme is unmentioned. It must be weak attractive forces, not strong repulsive forces.

 

[MedPR]

any solvent that has any sort of liquid form has attractive forces! i guess my question doesn't make sense :-x

the passage says that "strong attractive forces" is one extreme, and the other extreme is unmentioned. It must be weak attractive forces, not strong repulsive forces.

Strong nuclear
Weak nuclear
Gravitational
EM

Those are your only choices 🙂 So I guess weak nuclear is it.

 

[Dasypus]

Strong nuclear
Weak nuclear
Gravitational
EM

Those are your only choices 🙂 So I guess weak nuclear is it.

No. No no no. Those are the four 'big' force, yes. But two act *only* within atoms (strong and weak), and one only on the mega-scale (gravity).

All intermolecular forces are electromagnetic.

That said, there are different kinds of electromagnetic interactions possible between molecules in solution. Strongest is hydrogen bonding (e.g. water, ethanol); then dipole-dipole interaction (e.g. formaldehyde); then dipole-induced dipole interactions (which I don't think you'll get in a pure solvent); and finally London dispersion forces, which are interactions between instantaneous dipoles (e.g. benzene, CCl4).

(Exception-type note: there's actually another force you might think of, the attraction/repulsion of charged particles (ions), but that doesn't usually come into play, because you'll only get separated charges in a polar solvent, and there the dipoles of solvent surround the charged particles; that's what brings them into solution. If you could have a solvent that was made up of entirely charged molecules, then yes, the solvent would repell itself; but you can't, because that set of molecules would also have such a charge imbalance you couldn't build a container to hold it. It would blow itself, and you, to pieces.)

 

[MedPR]

No. No no no. Those are the four 'big' force, yes. But two act *only* within atoms (strong and weak), and one only on the mega-scale (gravity).

All intermolecular forces are electromagnetic.

That said, there are different kinds of electromagnetic interactions possible between molecules in solution. Strongest is hydrogen bonding (e.g. water, ethanol); then dipole-dipole interaction (e.g. formaldehyde); then dipole-induced dipole interactions (which I don't think you'll get in a pure solvent); and finally London dispersion forces, which are interactions between instantaneous dipoles (e.g. benzene, CCl4).

(Exception-type note: there's actually another force you might think of, the attraction/repulsion of charged particles (ions), but that doesn't usually come into play, because you'll only get separated charges in a polar solvent, and there the dipoles of solvent surround the charged particles; that's what brings them into solution. If you could have a solvent that was made up of entirely charged molecules, then yes, the solvent would repell itself; but you can't, because that set of molecules would also have such a charge imbalance you couldn't build a container to hold it. It would blow itself, and you, to pieces.)

Oh right, I forgot the context of this thread.

I agree that you won't have dipole-induced dipole in a pure solvent. If it's homogenous, then all of the molecules already have a dipole or don't have a dipole. No dipole = can't induce a dipole. Have dipole = have dipole already.