Solublity

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EP123

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Why is benzoic acid more soluble in methylene chloride (dichloromethane) than water?

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This seems like a tricky problem.

Benzoic acid does have a nonpolar benzene ring and a polar carboxyl group i guess you can call it amphipathic. I think the key here is that amphipathic molecules become increasingly less polar and less water soluble are their nonpolar component increases and dominates the overall character of the molecule. Carboxylic acids with 5 Cs or less are water soluble and benzene with 6 becomes less water soluble and more soluble in nonpolar solvents like dichloromethane.

Dichloromethane is interesting in that at first glance one could think its polar due to the presence of Cl but the electronegativity differential b/t C-Cl is only about 0.6 (bond symmetry may further reduce dipole moment). O-H on the other hand is 1.34 making water way too polar for solvating benzoic acid compared to the nonpolar dichloromethane.

I hope this makes sense.
 
Wow...that was very detailed but it made perfect sense. Thanks!
 
I'm glad it helped.

I like to be detailed in my explanation bcos personally I learn and recall best when I comprehend something at a fundamental level, then recall almost becomes commonsense or second-nature for me because it just makes sense.
 
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