why is commerical aspirin soluble in hydrochloric acid, but not in ethanol?

[liuetenant]

Yes, lol, this is for my aspirin sac...my school's enormously slow, but just wondering what the answer is, because i don't understand!

is it b/c the COO-NA+ ion bit stops it from dissolving in water? what about the other COOH OH parts?

also, why is salicyclic acid soluble in hydrochloric acid?

thankyou so much!

[homosapiens]

I think it's because commercial aspirin always has the Na+ ion attached for solubility, meaning it will dissolve in HCl due to ionic attraction. However ethanol only has a polar hydroxy group, in which the Na+ ion will not be soluble.

Also I'm pretty sure salicylic acid is soluble in HCl because it acts as a base, so it's an acid base reaction (the OH in salicylic acid reacts with HCl being the acid...)

[n.]

what do we write about the purity? before and after recrystallisation....

and what do we say about the melting points in relation to the purity???

[thatricksta]

woops misread, you are talking about commercial aspirin xD sorry, ill get some info though

ok, so apparently commercial aspirin will react with HCL as follows:
HO.C6H4.COONa + HCl -> HO.C6H4.COOH + NaCl

Looks awfully like an acid base reaction
http://faculty.ksu.edu.sa/MFarouk/Mfarouk%20PDF%20Library/Aspirin.pdf
This page also has information on the reaction and suggests it will convert the commercial aspirin back into normal aspirin (acetylsalicylic acid)

As far as ethanol is concerned, I don't believe its hydroxyl functional groups will react with Na

[thatricksta]

what do we write about the purity? before and after recrystallisation....

and what do we say about the melting points in relation to the purity???

the purity after crystalisation will be higher because it is no longer disolved in the solution. Before it crystalises you will have some aspirin dissolved in the solution, the addition of ice cold water will separate and crystalise the aspirin, thus increasing its purity.

Pure aspirin will melt between 134 and 136 degrees Celsius.
I believe that pure materials will have a really sharp melting point where as unpure materials will have a broad melting point, so if your aspirin is unpure, its melting temperature range will be larger than the 134-136 degrees of pure aspirin

I hope this is useful, I would appreciate it if someone confirmed this

[n.]

how about the purity before and after recrystallisation?

[thatricksta]

how about the purity before and after recrystallisation?

sorry!! I commonly misread things online because I have a form of dyslexia and I can't wear my glasses with a computer screen

We didn't do recrystalisation at school, but when you did it, did you use ethanol to dissolve the impurities?

Regardless of this, the entire point of recrystalising the aspirin is to increase its purity. As mentioned earlier, the purity of the substance will determine the range at which it melts over.

I think that covers everything!

[liuetenant]

thatricksta, u are awesome, thanks heaps for your contribution!

[n.]

yeah thanks for all your help

so what can we say about the solubility of the recrystallised aspirin? is it similar to the commercial aspirin?

[thatricksta]

yeah thanks for all your help

so what can we say about the solubility of the recrystallised aspirin? is it similar to the commercial aspirin?

The recrystalised aspirin you made in class is still going to be acetyl salicylic acid which does not have the Na group required to dissolve as nicely as commercial aspirin. This suggests that you may have difficulties dissolving this 'pure aspirin' in cold water...
Thats about all I can say really.

I wouldn't stress about aspirin too much. Know your stuff but it has been done so many times on previous exams that the likely-hood of it reappearing is not massive, but it could still happen