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Leo the Lion says Ger
Jun 17, 2016
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Can someone please explain that concept? I watched chad's videos and other videos on YouTube and I still don't seem to find a concrete set of rules for this.

when does the non-polar chain length matter, when does it not matter? why can you protinate NH2 and make it soluble in water but only if it has 3 carbons next to it? like what even are the rules?
 

orgoman22

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Can someone please explain that concept? I watched chad's videos and other videos on YouTube and I still don't seem to find a concrete set of rules for this.

when does the non-polar chain length matter, when does it not matter? why can you protinate NH2 and make it soluble in water but only if it has 3 carbons next to it? like what even are the rules?
As a rule of thumb. Amines or alcohols with less than 4 carbons are water soluble. If they have more than 4 carbons, they are considered Hydrophobic.

However, if O or N has a charge on it, then Amine or Alcohol is soluble, regardless of chain length.

Hope this helps.
 
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WheatLom

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Jul 6, 2016
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As a rule of thumb. Amines or alcohols with less than 4 carbons are water soluble. If they have more than 4 carbons, they are considered Hydrophobic.

However, if O or N has a charge on it, then Amine or Alcohol os soluble, regardless of chain length.

Hope this helps.

My text book says 5 carbons per functional group. So a 10 carbon chain with 3 -OH groups will be soluble.
 
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Hard Work Pays Off

Hard Work Pays Off

Leo the Lion says Ger
Jun 17, 2016
48
47
As a rule of thumb. Amines or alcohols with less than 4 carbons are water soluble. If they have more than 4 carbons, they are considered Hydrophobic.

However, if O or N has a charge on it, then Amine or Alcohol is soluble, regardless of chain length.

Hope this helps.
so, if I have CH3CH2CH2CH2OH it is hydrophobic and will end up in the organic layer but if I add a base to it that would extract the H, then it'll be soluble in water?
 

orgoman22

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Can someone please explain that concept? I watched chad's videos and other videos on YouTube and I still don't seem to find a concrete set of rules for this.

when does the non-polar chain length matter, when does it not matter? why can you protinate NH2 and make it soluble in water but only if it has 3 carbons next to it? like what even are the rules?
Updated response.

If you have 3 carbons or less with O or N on a chain.....it will be water soluble ! At 4 carbons......you push your luck. If 4 carbons and branched, such as t-butyl alcohol....it will be more soluble than 1-butanol. Protonating a molecule such as 1-pentanamine......would make it water soluble because you have put a HUGE positive charge on the nitrogen.....which can easily attract the water dipole. Hope this helps.
 
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WheatLom

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so, if I have CH3CH2CH2CH2OH it is hydrophobic and will end up in the organic layer but if I add a base to it that would extract the H, then it'll be soluble in water?

I want you to think this out, just in case you get into a situation on the exam.

The goal of extraction is to send one compound to the organic or aqueous layer. This can be done based on the method.

in theory.

The pKa of an alcohol is about 16, it may vary a little bit depending on substituents. So for butanol, you would need a base with a pKa higher than 16. This would mean the base is more basic or less acidic than butanol. When you deprotonate you have created a negative formal charge on the oxygen as it gains the electrons in total from the O-H bond. This charge will be very much able to be solvated by H2O in a solution, as the partial positive H of H-O-H will be able to be attached and surround the butoxide anion.


Lets say that you had it all in the aqueous form, you'd want to protonate the butoxide anion to send it to an organic layer.


Janice gorzynski smith's Organic Chemistry 4th edition text book does say, the general rule for solubility of a hydro carbon will be 5 carbons per functional group. The more carbons the less soluble so a 5C chain is less soluble than a 1C chain. But a 5C chain with 2 functional groups would help create more dipoles and increase solubility.
 
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orgoman22

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so, if I have CH3CH2CH2CH2OH it is hydrophobic and will end up in the organic layer but if I add a base to it that would extract the H, then it'll be soluble in water?
No. The procedure works only for acids and bases with a large difference in solubility between their charged and their uncharged form. When you do an extraction......we add a base to a molecule like a carboxy acid or even a phenol. Extraction doesn't work with the alcohol. You must realize that when you do an extraction, you are bringing a molecule from an organic phase to an aqueous phase,,,,,thus it must be sufficiently charged. Alcohols do not make the cut.

Hope this helps.

Dr. Romano