| Pages:
1
2 |
Keras
National Hazard
Posts: 896
Registered: 20-8-2018
Location: (48, 2)
Member Is Offline
|
|
Ah, right. But isn't phosphoric acid more suitable for that?
|
|
|
Texium
Administrator
Posts: 4580
Registered: 11-1-2014
Location: Salt Lake City
Member Is Offline
Mood: PhD candidate!
|
|
Either will work
|
|
|
Keras
National Hazard
Posts: 896
Registered: 20-8-2018
Location: (48, 2)
Member Is Offline
|
|
Ether will work :p
Pun aside, how do you mix styrene with water? You use a surfactant? A phase-transfer catalyst such as TBAB? Use a steam bubbler into styrene?
[Edited on 30-5-2022 by Keras]
|
|
|
Keras
National Hazard
Posts: 896
Registered: 20-8-2018
Location: (48, 2)
Member Is Offline
|
|
Quote: Originally posted by Fyndium  | | I would be very glad if you'd post a report of your process. I looked up for this synthesis a long time ago, but sort of buried it due to not finding
any lucrative material. |
So, I had finally some time to try out that experiment.
40 mL of tetrahydrofuran + 5 g of styrene (~ 50 mmol) + 0.76 g of sodium borohydride (~ 20 mmol) are placed in a 250 mL r.b.f. on a magnetic stirrer.
I was a big moron, I didn't use a funnel to shove the borohydride in, and a few milligrams of it got stuck in the neck. That didn't matter much,
because it is in excess, but as a matter of principle it was bad. The r.b.f is placed in an ice-bath (optionally ice-salt) a Claisen adapter is
mounted atop of it with, on the one side, a pressure-equalised dropping funnel and, on the other side, a condenser whose output is fed to a bubbler
(Drechsel bottle) filled with mineral oil. The dropping funnel is filled with a solution of 2.91 g of iodine in a bit less of 10 mL of tetrahydrofuran
(the original recipe calls for 15 mL, but I only have 10 or 50 mL dropping funnels, so I went for 10 mL).
The dropping funnel is stoppered and set to about one drop every five seconds. Stirring is started. Each drop of the iodine solution causes a brief
yellow colouring that promptly (1, 2s) fades. The formation of borane results in hydrogen being generated, but the bubbler never really bubbles,
either because the volume generated is minimal, or because the simultaneous cooling of the flask keeps the volume in check. The iodine coloration
persists a bit more towards the end of the addition, but always fades after several seconds.
Once all the iodine solution has been added, the ice bath is removed and the reaction is allowed to carry on for 90 min at r.t. The solution is clear,
and there’s no visible change.
After 90 min, a new ice bath is set, the flask is allowed to cool (~ 10 min) and everything atop the flask is dismantled. 25 mL of distilled water are
dropped into the r.b.f in four or five portions, each addition resulting in a brief fizz of hydrogen as the excess hydride decomposes. Then 5 mL of a
3 M NaOH (= 0.6 g of NaOH) is added, followed almost immediately by 6 g of sodium percarbonate ca. This seems to be an excess to what is needed.
Logically, there could be no more than 50 mmol of final product, so 60 mmol of hydrogen peroxide is enough to completely oxidise the intermediate, and
that’s what the original recipe goes for, but under the form of sodium perborate. Since each mole of sodium percarbonate contains 3 moles of
hydrogen peroxide, 20 mmol is probably enough. I’m not entirely sure, though.
Note that the sodium carbonate contained in the sodium percarbonate might also be basic enough for the oxidation to work without adding sodium
hydroxide. I wasn't certain, however, so I stuck to the original procedure.
After 2 or 3 min the temperature of the flask steadily rises and reaches about 25 °C as the oxidation proceeds. The original recipes says the
reaction is over when all the perborate has dissolved. In this case, there was too much sodium carbonate for the 25 mL of water to dissolve completely
so I had to watch the thermometer. After 15 min or so the temperature drops again, and I took that as the signal the reaction was over. At the end of
the oxidation reaction, the solution turns yellow, then brown, meaning that the iodide ions are oxidised back into iodine, and that seems to be
another clue that all the boron complex has been oxidised. I’m, however, still wondering if there was hydrogen peroxide enough – solubility of
sodium percabonate is given to be slightly less than 1 mol/L, so 25 mL cannot dissolve more than 25 mmol. Can hydrogen peroxide be ‘leeched’ out
of the compound in solid form, I have no idea. It might be best to increase the volume of water (say, 35 mL instead of 25 mL) to be on the safe side,
though the oxidation of iodine could be a telltale that there was hydrogen peroxide enough.
So once the oxidation reaction is seemingly over, a sodium thiosulphate aqueous solution is added until the flask has completely lost its yellow
tinge. The r.b.f is then decanted into a sep funnel. Water is heavier than tetrahydrofuran, so the organic layer sits on top. It is cloudy at first,
but after 10 min or so all the water has collected below and the upper layer should be almost crystal clear. The lower layer is collected and
discarded, unless you want to recover the couple of grams of iodine trapped inside, which I didn't do but is sensible given the price and difficulties
to source iodine. The upper layer is collected in turn, and the solvent is removed, in my case by simple distillation with a short path apparatus. I
recovered a bit more than 40 mL of tetrahydrofuran, but I let the temperature rise up to 80 °C. If I had stopped as soon as it began rising over 66
°C, I would've been nearer to 30 mL. I suspect the last 10 mL contains water, so I saved the tetrahydrofuran in a flask over calcium chloride to dry
it. The lost 10 mL must've gone into the water layer, or just were lost as vapour, because distillation was pretty fast.
What remains in the flask after all the tetrahydrofuran has distilled out is several mL of a sort of syrupy compound, creamy in colour (but that might
be due to leftover traces of iodine). It doesn’t smell of styrene at all, but I have a hard time qualifying it as ‘rose perfume’, though it has
some overtones of it. To me, it is closer to the scent of freshly cut mushrooms. On the other hand, the hydroboration of styrene is known to be less
regioselective than normal hydroborations, producing up to 20 % of 1-phenethyl alcool, which has a different smell.
PS: It is a priori easy to separate 1- from 2-phenethyl alcohol. Just put both in the freezer. 1- will solidify, and 2- remain liquid.
[Edited on 7-6-2022 by Keras]
|
|
|
clearly_not_atara
International Hazard
Posts: 2787
Registered: 3-11-2013
Member Is Offline
Mood: Big
|
|
Re: subject:
https://en.wikipedia.org/wiki/Prins_reaction
Phenylpropane-1,3-diol could eliminate to hydrocinnamyl alcohol (NaHSO4, heat) and be oxidized with MnO2 to cinnamaldehyde. Seems clever.
|
|
|
Fantasma4500
International Hazard
Posts: 1681
Registered: 12-12-2012
Location: Dysrope (aka europe)
Member Is Offline
Mood: dangerously practical
|
|
| Quote: Originally posted by Tsjerk | | Quote: Originally posted by Antiswat | Tsjerk
very easy. mix it lol
theres also some H2SO4 in it, not sure if that does anything- but it gets warm right away, upon standing you get benzoic acid- i suppose dumping in
some hexane after a bit of time would get you benzaldehyde in hexane, then just distill off the hexane
if you fancy driving a bit, then you might be able to buy 1000L 30% H2CrO4 solution and more, check reagents and acquisition |
Mix it lol would be the summary of any write-up, literally. Please detail the procedure a bit more so your post will bear meaning. Reaction conditions
are a minimum, yields as well. Without you could as well have posted nothing. |
so i found the following. 100g CrO3 in water, H2CrO4, tip this up to 300mL and you have .. 39.3% H2CrO4
this reacts with just about 100mL BnOH to form - seemingly 100mL BnH - benzaldehyde in a ration of 100 mL BnOH to 185mL 39.3% H2CrO4
this reacts basically instantly, i believe i cooled down the mixture about 3-4 times while adding it. its a very warm reaction so no need to heat on
it.
this was then extracted in rounds of 3 or 4 times using hexane-heptane fraction acquired from fractionally distilling gasoline, i believe its
80-100ish fraction, 95 maybe
seperating this was rather easy, simply distill off the solvent and youre left with rather pure BnH
i have no clue how to deal with the chromium waste however. basifying it makes it entirely impossible to filter. entirely. and BnH is detectable at
0.04ppm while its slightly toxic- leaving it to dry out is not an option for me. the sludge also sucks up a bit of solvent so its inevitable that it
will always keep a bit of aromatics locked up
the sludge is supposedly Cr(III) - hydroxide, chloride. i tried eliminating t he rest of the chromate by acidifying and adding EtOH which seems to
react decently fast. ascorbic acid may also be used, i need to look into what FeSO4 produces with chromate ions, i recall seeing that used to reduce
it into Cr(III) state- i hate throwing out waste so i hope i can find a solution for dealing with the byproducts.
|
|
|
SplendidAcylation
Hazard to Others
Posts: 203
Registered: 28-10-2018
Location: Starving in some deep mystery
Member Is Offline
Mood: No one I think is in my tree.
|
|
Hydration of styrene
I have been looking for something useful to do with styrene for a while, so I can have some excuse to make it from polystyrene I have lying around.
Do you suppose that this hydration would be as simple and effective as it seems? I wonder why no one has really discussed the preparation of
1-phenylethanol from styrene here.
Once we have 1-phenylethanol, the most obvious interesting project would be the oxidation of the secondary alcohol to the ketone, acetophenone:
http://www.sciencemadness.org/talk/files.php?pid=506841&...
[Edited on 6-4-2023 by SplendidAcylation]
|
|
|
| Pages:
1
2 |
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
