How is the hydrophobic effect entropic?

[Gauss44]

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I don't understand how the hydrophobic effect demonstrated by oil separating from water or by hydrophobic portions of a protein folding away from an aqueous environment, is driven by entrophy? Can you explain?

My misunderstanding is that oil separating from water would cause the system to be MORE organized, and have no effect on the surroundings. So how does entrophy increase in that situation, if it does? What am I missing?

 

[Jepstein30]

I don't understand how the hydrophobic effect demonstrated by oil separating from water or by hydrophobic portions of a protein folding away from an aqueous environment, is driven by entrophy? Can you explain?

My misunderstanding is that oil separating from water would cause the system to be MORE organized, and have no effect on the surroundings. So how does entrophy increase in that situation, if it does? What am I missing?

My thinking would be:

Oil mixed with water = you'll get water molecules surrounded by oil and since they don't interact, they will effectively be 'stuck' in that orientation
Oil separated with water = now you have water molecules that will interact with other water molecules via H-bonds.. but since every H-bond is as strong as the other, they don't actually just sit there locked in one orientation.. they are constantly flip-flopping and moving around = more disorder

entropy increases when you have more possible orientations.. think gas vs. solids. Gases have more entropy because of all those interactions b/w gas molecules have more possible orientations whereas a solid is a lattice structure.. basically stuck in that state.

 

[sazerac]

Jepstein has it right. More ability to form hydrogen bonds at the molecular level means more entropy.

Surprisingly this is more entropy than you would get by emulsifying the oil and water (and limiting the ability to hydrogen bond water).