Can something that dissolves in water be hydrophobic?

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SUMMARY

The discussion centers on the solubility and hydrophobicity of H2CO3 (carbonic acid) in water, specifically questioning whether H2CO3 molecules can exhibit hydrophobic properties. Participants clarify that dissolved substances are typically uniformly distributed in solution, and concentration gradients occur only under specific conditions. The conversation also touches on the concept of "salting out," where ionic strength is increased to drive hydrophobic organic pollutants to the surface, contrasting this with the behavior of CO2 in water. Ultimately, it is established that altering a molecule's hydrophobicity generally requires changing the molecule itself.

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  • Understanding of solubility and hydrophobicity concepts
  • Familiarity with carbonic acid (H2CO3) and its behavior in aqueous solutions
  • Knowledge of "salting out" techniques and their applications
  • Basic principles of molecular structure and properties
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  • Research the mechanisms of "salting out" and its applications in environmental science
  • Explore the properties of carbonic acid and its interactions in aqueous solutions
  • Investigate methods for modifying molecular properties, particularly in organic chemistry
  • Learn about the behavior of hydrophobic pollutants in water treatment processes
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Chemists, environmental scientists, and researchers interested in molecular behavior in solutions, particularly those studying hydrophobic interactions and water treatment methods.

rwooduk
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This may be a really stupid question, but I'm going to go ahead anyway.

Say I have CO2 and dissolve it in water to give H2CO3, are / could the H2CO3 molecules be hydrophobic?

To put this in context I want to somehow drive the H2CO3 molecules to the surface of the liquid. Does this make sense? Would this be possible?
 
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rwooduk said:
Does this make sense?

Not much. Whatever is dissolved is more or less uniformly distributed. Sure, there can be a concentration gradient, but that happens when there is no mixing and you either add or remove the substance on the solution surface. Otherwise it is unlikely.
 
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Borek said:
Not much. Whatever is dissolved is more or less uniformly distributed. Sure, there can be a concentration gradient, but that happens when there is no mixing and you either add or remove the substance on the solution surface. Otherwise it is unlikely.

That's very helpful, thanks!

To be more specific, I am reading a paper that uses salt to increase the ionic strength of a liquid, so that hydrophobic organic pollutants in the liquid are driven to the surface. Please could you lend some insight into how this differs from the CO2 case above?

Again, apologies if this makes little sense.
 
Borek said:

Interesting. I see it has a similar method.

Do you know of any methods to make a particular molecule hydrophobic, so that it could be "salted out"?
 
I general you can't change properties of a molecule* without changing the molecule itself.

*At least for small, simple ones. when it comes to large ones like proteins things get more complicated, as a lot depends on what you mean by "changing" the molecule.
 
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Borek said:
I general you can't change properties of a molecule* without changing the molecule itself.

*At least for small, simple ones. when it comes to large ones like proteins things get more complicated, as a lot depends on what you mean by "changing" the molecule.

Hm, that's unfortunate, but okay you have been very helpful, thanks again!
 

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