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Topic: Solubility of organic compounds  (Read 12007 times)

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Offline vanilla999

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Solubility of organic compounds
« on: February 27, 2011, 08:56:29 PM »
Rank their solubilities from lowest to highest: Hydrocarbons, aldehydes, alcohols, carboxylic acids

I know that hydrocarbons is the lowest - it cannot form H bonds with itself nor can it form H bonds with water.

For the other 3, though, I'm not sure which one has a stronger solubility over the other two.
They are all soluble because they can form H-bonds with water even though they might not be able to form H bonds with itself (aldehydes).

All their solubilities fall as the length of their hydrocarbon chains increase, so I'm not sure how to rank the last 3.
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Offline Schrödinger

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Re: Solubility of organic compounds
« Reply #1 on: February 27, 2011, 11:18:40 PM »
It's not H-bonds alone that need to be considered. Acids, for instance dissociate in water to produce ions. That way, the carboxylic acid is the most soluble among the 4. Alcohols come 2nd, since they have a hydrogen attached to the oxygen, and hence greater number of hydrogen bonds can be formed when compared to the aldehyde.
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Offline rabolisk

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Re: Solubility of organic compounds
« Reply #2 on: February 28, 2011, 04:06:00 AM »
I agree with Schrodinger. If you compared butanal (butyraldehyde), 1-butanol, and propanoic acid, all with MW ~ 70, the solubility data agrees with carboxylic acid > alcohol > aldehyde.
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Offline sjb

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Re: Solubility of organic compounds
« Reply #3 on: February 28, 2011, 04:29:21 AM »
Quote from: vanilla999 on February 27, 2011, 08:56:29 PM
Rank their solubilities from lowest to highest: Hydrocarbons, aldehydes, alcohols, carboxylic acids

Playing devil's advocate here, but solubility in what? Ranking in petrol will be (very) different to ranking in water.
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Offline rabolisk

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Re: Solubility of organic compounds
« Reply #4 on: February 28, 2011, 04:48:40 AM »
Quote from: sjb on February 28, 2011, 04:29:21 AM
Quote from: vanilla999 on February 27, 2011, 08:56:29 PM
Rank their solubilities from lowest to highest: Hydrocarbons, aldehydes, alcohols, carboxylic acids

Playing devil's advocate here, but solubility in what? Ranking in petrol will be (very) different to ranking in water.

True, but I think most people associate solubility with water by default when no solvent is explicitly stated. For example, when people talk about solubility rules for salts, they mean solubility in water, but that is assumed. Unless there is some context which suggests that we are talking about solvents other than water, I believe it is safe to assume that water is the solvent.
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Offline AMEDIO

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Re: Solubility of organic compounds
« Reply #5 on: February 28, 2011, 09:00:16 AM »
Quote from: sjb on February 28, 2011, 04:29:21 AM
Quote from: vanilla999 on February 27, 2011, 08:56:29 PM
Rank their solubilities from lowest to highest: Hydrocarbons, aldehydes, alcohols, carboxylic acids

Playing devil's advocate here, but solubility in what? Ranking in petrol will be (very) different to ranking in water.

a very good point made...
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