syntheticvibes
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Posts: 14
Registered: 21-6-2021
Location: Oregon City, OR
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Mood: Full of thought
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Contaminated 1-indanone sample
Hi all,
I work closely with the lab coordinator at my community college. We received a bottle of 1-indanone last year that is dark brown and somewhat sticky.
1-indanone is usually described as clear to yellow, but occasionally as brown. In a dry-aldol reaction the students to, the yields from the darker
sample were lower than the ones done with our older, but clearer, 1-indanone. I was tasked with the semi-trivial task of trying to find a way to clean
up this sample. Most of my o-chem lab "experience" was at the height of covid, so I only got to do about 6 lab sessions in person, so I'm a bit rusty
on separation.
I ran a rough TLC and paper chromatography on the sample with nonpolar and polar solvents, respectively, and a spot moved up the plate/paper in each
scenario, leaving another behind.
Our FTIR and NMR machines are down for the count, so I don't have any imaging.
A MP test showed that the colored solid melted about 4-6 deg C sooner than expected for 1-indanone, where our purer-looking solid melted when expected
(38-42 deg C).
I've ran two rough extractions in large volumes of water heated to 50-80 deg C, allowed the solution to stir for a period of time (the second time
much longer than the first), as 1-indanone has a solubility in water of 6.5g/L. Each time, the crystals began to liquefy and act as oily blobs which
spun around at the bottom of the beaker.
After heating, the solutions were allowed to filter through a funnel, where the brown floating stuff left behind was allowed to collect. Each time,
these brown blobs were darker than the original sample and recrystallized.
In the first extraction which spent much less time stirring (about 10 minutes) at about 50 deg C, I placed the beaker in the lab dryer at 35 deg C for
almost a week. Once the water was dry, we had some nicer white crystals and a yellowish oil. This oily liquid has so far refused to recrystallize.
Right now it's in our lab freezer.
In the second extraction which was carried out at a higher water volume and about the amount of 1-indanone to make it, hypothetically, completely
dissolve (6.5g in 1 L water). This mixture stirred at a higher rate for nearly 3 hours around 80 deg C. This time, the yellowish-brown color ended up
in smaller almost well-mixed beads, but when allowed to collect were much browner than the time before. All the color for the most part was removed
from the liquid.
These sat in my lab dryer overnight at 75 deg C, and it was reported to me this morning that the dishes were dry except a "residue" on the bottom. I
don't have photos nor a color description.
I'm going to take a look at this later when I'm in person, but for now I have a few questions:
1) What might be a better approach than the one I'm taking? Do you have any recommended extraction techniques? Maybe a reaction and re-synthesis?
2) Why won't my oil recrystallize? My instructor said that it might not because once things are oils it's hard to get them to crystallize. Any
recommendations for getting this to recrystallize?
3) What other things could be contaminating my 1-indanone? Common derivatives? Indene is a flammable pale-yellow oil, which matches the description of
the oils that are in with my crystals from the first trial. Could this be indene? I suppose all I'd have to do is try to light it on fire haha.
I don't have a picture of any of this right now, otherwise I would upload one. When/if I get back to the lab before I have a sufficient answer, I'll
get back to you. Thanks friends!
"I placed the sand as the boundary for the sea,
a perpetual barrier that it cannot pass;
though the waves toss, they cannot prevail;
though they roar, they cannot pass over it."
- Jeremiah 5:22b
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Metacelsus
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Registered: 26-12-2012
Location: Boston, MA
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Mood: Double, double, toil and trouble
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A vacuum distillation might work if you have the equipment for it. See: https://www.orgsyn.org/demo.aspx?prep=CV2P0336
"After the benzene is removed by vacuum distillation on the steam bath, the α-hydrindone is distilled. It boils at 125–126°/17 mm., and the
distillate is a pale yellow solid, m.p. 39–41°."
[Edited on 2023-11-22 by Metacelsus]
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Fery
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Posts: 1026
Registered: 27-8-2019
Location: Czechoslovakia
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It has quite low melting point so it oils out during recrystallization especially if the solvent is warmer than m.p. If you perform a vacuum
distillation as Metacelsus suggested you, do not use too cold water in condenser circulation to prevent clogging the condenser. Cheap ebay 200 EUR
2-stage oil rotary vane vacuum pump should be powerful enough to lower its b.p. below 100 C. In the link there is also a crystallization method (see
note 5), but the distillation has an advantage that the product is completely dry.
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