It is rumored here and there that neglected on the shelf some acetylsalicylic acid in aspirin reverts to salicylic acid.
I should like to hasten this reaction. I want some salicylic acid for some armature horticultural experiments.
I have been away from the laboratory for decades.
Are there any organic chemistry students here who could describe a kitchen procedure to get a bottle of Walmart aspirin to deteriorate or revert to salicylic acid?
Well, it’s an ester hyrolysis, which I believe can be catalyzed by either acid or base. But why not just by some salicylic acid-containing product?
Excellent suggestion. I will go looking for a suitable product.
In the meantime do you know if there OTC products containing any more salicylic acid than USP aspirin that are sold in a water soluble medium? Would it not be difficult to extract salicylic acid from cosmetics? I wonder if Pepto-Bismol were mixed in a weak acid would I get a salicylic acid solution?
I wonder exactly what armature experiments are? Or, do you possibly mean amateur? What do you have in mind?
I suspect that simply boiling the aspirin in water for several hours will do it. It will certainly be accellerated by raising or lowering the pH, either by adding an acid (say vinegar) or a base (e.g. washing soda) - though I wouldnt feed that mixture to a plant without adjusting the pH back.
To tell whether it has worked do it in a concentrated solution. Pure aspirin is poorly soluble and will come out of solution when cold. The acid is much more soluble so if the solution satys clear when cooled is a good indication/
How much do you need?
Salicylic acid would be fairly easy to extract from most things that it is a major component. You just need to know how. You also need access to acids, bases and an organic solvent. It helps to actually know what you are doing.
Hydrolysis of aspirin is also very easy. Don’t bother with acid, it works theoretically but practically sucks. I think hydrolyzing with water as a solvent would also be difficult due to the aforementioned solubility issues of aspirin. Since this type of reaction in organic solvent requires a hood and proper equipment due to an extreme fire hazard, I don’t think I would recommend it. Have fun convincing the authorities you aren’t making meth.
While we’re at it, how does the reaction work the other way? Could I make something resembling aspirin by soaking or boiling willow-bark extract in vinegar, or is it (I imagine probably) more complicated than that?
Yes you could, but your yield would be awful. Esterification is a dehydration reaction, involving the release of a water molecule. A watery solvent, such as your boiling vinegar, encourages the reverse reaction, hydrolyis of the ester.
You’d be better off boiling your willow bark in glacial acetic acid, with a little H[sub]2[/sub]SO[sub]4[/sub] in there to suck up any released water. If you don’t want to mess with H[sub]2[/sub]SO[sub]4[/sub], boiling your willow bark in acetic anhydride would also give you the ester.
Don’t be so hasty Squink, there has been a metric buttload of research in water based chemistry dehydration reactions are no exception. In particular, sulfonic acid and rare earth metal catalysts have been effective in making esters from carboxylic acids and alcohols.
In just a minute, I’ll remember the name, but right now I know it starts with a K and is Japanese.
Of course, you wont do this very well in the kitchen.
ETA: Kobayashi
Actually, no it wouldn’t, not in the case of Aspirin. Attempts at performing those reactions got the anhydride instead. To make o-acetylsalicylic acid, you first need to protect the acid, then esterify, then remove the protecting group.
Ohh the joys of actually cooking some up!
There’s always a nasty side reaction waiting in the wings.
So much trouble, these reactions.
$42 for half a kilo. Not bad if you just want a little to play around with.
I partially kid - I’ve ordered from SA before, but I doubt if they’ll ship to you unless you’re in their “chemical company or academic institution” database.
I wonder what kind of horticultural experiments might need salicylic acid? I’m not trying to dissuade or second-guess the OP; I’m just both curious and clueless on this stuff.
Perhaps something like this:
Methyl Salicylate is a Critical Mobile Signal for Plant Systemic Acquired Resistance.
My favorite chemist by that name is the ever-stylish Shū Kobayashi. Glorius is his neckbeard. And he does some pretty swell organometallic chemistry.
Why not just boil willow bark the way the Greeks used to do? Shouldn’t be hard to find a source either in nature or online.
Not surprisingly then, he is one and the same. As I was an organometallic chemist in grad school, I am also a big fan. Here is the paper I mentioned
I don’t remember a beard, but I haven’t seen him in a long time. On looking him up, I see why I didn’t notice it. It really is a neckbeard. I probably just saw it as a shadow from the podium. I never did get the chance to meet him.
OK, so I guess if I ever get stranded in the Middle Ages by a malfunctioning time machine, I probably won’t be able to cook up a miracle headache cure. Back to the drawing board, then.
I have read the replies and rethought the experiment and returned to my original idea.
Hear is why. The plant hobbyists information, online and in print, is glut with tips ranging from the invaluable to the ridiculous. Among the recurrent suggestion is to add aspirin to water for propagation. If this is useful it might be because of traces salicylic acid.
(Willow water may contain IBA so that is not a good source of salicylic acid for these first experiments.)
Again, it is rumored that on the shelf acetylsalicylic acid changes to salicylic acid, this may not be true either. If this is the case, I would like to hasten the process of acetylsalicylic acid to salicylic acid.
It’s not a rumor, it’s actually true. This is why bottles of aspirin have a vinegary odor to them that increases with age. The acetylsalicylic aspirin loses the acetic acid (vinegar) leaving just the salicylate. Not sure how you’d hasten the reaction… perhaps rinse the tablets in water to get rid of any moisture-resistant coating, then lightly dry and store them in a warm place for a few weeks.