So, for fun I made some Rheosmin a few weeks ago. Since 4-OH-benzaldehyde is easily available, I decided to start from 50g of it (0.41mol).
I mixed it up with 200cm3 acetone, 20g NaOH dissolved in 100cm3 water and let it stand for the weekend.
On monday the solution looked like this:
Than I acidified it with 200cm3 of 10% HCl and filtered it out, washed twice with water and once with methanol:
I have not measured the amount of the reaction product, I immediately started the next step. The orange/yellow mass was dissolved in 200cm3 of ethyl
acetate, right after dissolving it, some Na2SO4 (the yellowish solid at the bottom) was added to remove the remaining water:
After standing there for one hour, the solution was filtered, the Na2SO4 was washed with 50cm3 of ethyl acetate and the whole organic stuff was added
to a hydrogenation vessel with 1g previously activated 10% Pd/C and shaken with it until it have ate 8650cm3 hydrogen.
The hydrogen was blown off, replaced with argon, the reaction mixture was filtered on a Celite pad and evaporated to give a ivory colored solid with a
really weak odor.
This solid was recrytallized from 3000cm3 of distilled water to give these nice crystals what have absolutely no odor of raspberry, and according to
the NMR spectra it's 99% what I wanted (1% gunk).
Overall yield: 85%.
Anyone has any idea that how could I make the rheosmin "smelly"?Adas - 7-4-2013 at 00:45
This is very strange. Try heating up a few crystals to see what happens.Nicodem - 7-4-2013 at 02:57
Interesting problem. With smells it is best to double check with another human. It might be you are a mutant unable to smell rheosmin. I find it
extremely unlikely, but mutants lacking the ability to sense specific smells are very common in the human species.
This solid was recrytallized from 3000cm3 of distilled water to give these nice crystals what have absolutely no odor of raspberry, and according to
the NMR spectra it's 99% what I wanted (1% gunk).
Can you please post the spectra (either as the FID, a *.mrc file or just a picture)?DJF90 - 7-4-2013 at 03:35
I too would like to see the spectra. I have no software on my home computer, so if you could post an image of it that would be appreciated. I'm not
saying you've got it wrong, I just want to see for myself, if that makes sense.
Quote:
This solid was recrytallized from 3000cm3 of distilled water to give these nice crystals what have absolutely no odor of raspberry, and according to
the NMR spectra it's 99% what I wanted (1% gunk).
And you quantified that against an internal standard did you (if so which one)? turd - 7-4-2013 at 07:38
Well, I never held this particular compound in my hands - but I am not very surprised.
Many pure well-crystallized solids do not have a significant vapor pressure (iodine and benzoquinone being notable exceptions). For example high
purity recrystallized vanillin and various other solid alkoxy-benzaldehydes feature a characteristic, but very subtle smell.
Moreover, I find that often pure compounds smell much less intense than mixtures even if the former are volatile. This is for example true for
selenides and tellurides. They certainly smell bad, but an undefined mixture makes me run right to the toilet. I have no plausible explanation for
that.
The science of smells is certainly very complex.
[Edited on 7-4-2013 by turd]mr.crow - 7-4-2013 at 09:17
Try dissolving it in alcohol to make a really cheap nasty perfume.
What is that hydrogenation vessel called? I have never seen one like it.kristofvagyok - 8-4-2013 at 13:01
Sorry for the late reply, but I couldn't reach the NMR spectras... Now it's here as jpg, everyone could see it.
The hydrogenation vessel is called "hydrogenation duck" at us, but it's just a shaken vessel what was previously filled with argon, flushed twice with
hydrogen and the absorption the H2 is measured by a gas burette. Simple and practical.
The metal thing at the end is just the holder.
I have also tried to melt it, it only had a little odor what was more similar to cheap fruity fizzing tablets than raspberry... And circa 10 people
have smelled it and said that this is a big nothing. Samle when dissolving it in EtAc and gour it on something....
DJF90 - 9-4-2013 at 12:37
I'm befuddled. The carbon spectra looks good. The proton is fairly good too, although not too happy about the splitting pattern for the two aliphatic
CH's. It might be that thats how it is, though I was expecting to see two triplets. It could be that we're observing long range coupling. I'm also
suprised how sharp and well integrated the phenolic proton is.
Its nice to see theres no water in your spectrum, despite using this as the solvent for your recryst. You must have dried the crystals well!
[Edited on 9-4-2013 by DJF90]mnick12 - 9-4-2013 at 14:29
For a while I was fooling around with rheosmin and zingerone derivatives. I found that the "clean" (this would include catalytic hydrogenation)
methods for producing these compounds produced a less interesting mix of products, which had a relatively week smell. However I began fussing around
with other reducing methods like Zn and AcOH which after work up produced a fragrant gooey blob. It did not really smell like raspberries, but it
defiantly smelled fruity. I never tried to purify the stuff because I was happy with the way it smelled and I only had around 100-200mg of the goo.
On another occasion I attempted a catalytic hydrogenation of dehydrozingerone in methanol (I think) with 5%Pd/C. I ended letting it go to long and the
product was a clumpy crystalline yellow compound that smelled of ginger, and a thick oil that was absorbed by the filter paper. My guess was it was
the saturated alcohol or something similar, but the combination of the products smelled quite nice.
One thing you may try is to drop a few mg of the stuff on a hotplate and take a whiff. I did this when I tried to make rheosmin because I thought it
had a week smell too. kristofvagyok - 10-4-2013 at 13:56
It would be interesting to know that is the "rheosmin" is the odorous substance or something else what is generated next to it while working with
it...
By the way, thank you for all the replies!Random - 11-4-2013 at 06:43
It would be interesting to know that is the "rheosmin" is the odorous substance or something else what is generated next to it while working with
it...
By the way, thank you for all the replies!
You should ask those who consume raspberry ketones as a weightloss supplement (which actually doesn't work), if the smell is very strong. Maybe on
some fitness forum? What they consume is synthetic and should be quite pure.Mailinmypocket - 2-8-2013 at 12:06
For what it's worth, I can say that supplements with raspberry ketone do smell nice and like fresh raspberries/raspberry chocolates... Do they work?
No clue... I could never commit to something as involved as taking 2 tablets twice daily :S but for the small amount present in these capsules the
smell is very strong!
