dex
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How do Butyrate Esters smell to you?
I just made heptyl butyrate, to me it smells very fruity, sweet and has a really intoxicating smell. I had a friend take a whiff off a Q-tip I scraped
the walls of the flask with, and he says it smells like vomit. I agree that butyric acid has a rancid smell, but I've washed the product once and I
can't detect the faintest hint of vomit. He says he can detect a bit of a fruity/chemical undertone but the vomit part affected him to the point of
making him retch. Maybe I got nose-blind but I can still smell vomit from the butyric acid bottle so I don't know. Maybe he's extra sensitive to these
smells.
So I wonder, if some of you have had a similar experience, with butyrate esters or anything in general that you feel you smell differently from most
people.
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Fery
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Washing with NaHCO3 during workup gets rid of butyric acid.
https://www.sciencemadness.org/whisper/viewthread.php?tid=15...
Today I would use 10x less H2SO4 catalyst and finally vacuum distillation.
n-pentanoic acid has much worse scent than n-butanoic acid
I tried to sniff butyric acid from 1 L bottle and it was not so much terrible as I expected. More diluted scents are sometimes worse than concentrated
(concentrated scent sometimes very likely saturates olfactory receptors into blocking state).
[Edited on 26-10-2025 by Fery]
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dex
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Thanks Fery, I came across your thread a while ago when researching how to do this 
I eyeballed a very tiny amount of H2SO4 (<1mL) and did not get any tar at all. I introduced excess butyric acid. Also, I did not have a DS
apparatus and just put a lot of MgSO4 and stirred on a heating mantle for an hour or so until it became so bulky it blocked the stir bar. I tried
simple fractional distillation but it was boiling too violently and separating poorly (sharp oil-like pops sending vapor all the way to the middle of
the condenser). I washed with NaHCO3 in a sep funnel until it stopped bubbling, it went from slightly milky to perfectly clear, but looking back I
could've done a second / third wash. Apparently sodium butyrate also has a smell problem, maybe the water got too saturated and some sodium butyrate
stayed in the ester. I got around 50-60% yield. I think my friend is very sensitive to the smell of butyric acid and could smell the impurity. I'll
just leave it until I acquire a vacuum pump, then I'll try vacuum distillation, and wash it again, and I'll update you on the smell.
I also find that butyric acid doesn't smell that bad when smelling it from the bottle.
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Fery
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Perhaps you can just filter your product through a column of KHCO3 or NaHCO3 to get rid of butyric acid. Or just add some very fine grounded dust of
bicarbonate into stoppered flask with your product and let it magnetically stirred for few hours? Then ask your friend to sniff whether it helped or
not.
You did well that you added only tiny amount of H2SO4. I added too much (5 ml) which at the end - as reaction water (1 mol which is 18 g) was removed
by azeotropical method, the reconcentrated H2SO4 started to oxidize organic compounds, create tar, and the dense insoluble H2SO4 separated as bottom
phase.
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dex
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I think washing it twice with aqueous NaHCO3 did the trick, but now my friend has associated the smell of the product with the smell of vomit and he
says he dislikes smelling it, even though he doesn't smell any vomit anymore. Now I've grown tired of smelling it too, I think it smells weird and
even a tiny bit on a qtip is making me sick. Another friend who hadn't smelled it until now thought it smelled really nice and fruity. Funny how that
works.
And yes, about the H2SO4, it was from your thread that I got the idea not to add too much H2SO4
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Dr.Bob
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It only takes a part per million of butyric acid to smell bad, but you can get used to it. I have worked with it, and had to be careful not to get
it on me and have people run from me...
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dex
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Quote: Originally posted by Dr.Bob  | | It only takes a part per million of butyric acid to smell bad, but you can get used to it. I have worked with it, and had to be careful not to get
it on me and have people run from me... |
It's funny because I did the esterification in my bedroom and it got into my jacket, and when I came back to uni one of my friends who was apparently
also very sensitive to the smell would retch just from sitting next to me 
Lesson well learned!
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chloric1
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For this reason, I’d do ester reaction outdoors. Even if the ester smells nice it can still be overpowering. I’m partial to butyl acetate, it
smells like candy and it’s less noxious than MEK or xylene so I use it to spray oil and alkyd paints. Often mixed with alkanes like naphtha or
white spirits.
Fellow molecular manipulator
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