hydroquinone oxidation via NaNO2 / HCL

[blaaky]

This method is mentioned in Rhodium's p-benzo page (

https://www.thevespiary.org/rhodium/Rhodium/chemistry/benzoquinone.html

)
but TFSE doesn't turn up anyone ever using this method.

I trid to follow the synth to the letter: 24.4g hydroquinone and 345mg of NaNO2 suspended in 100mL technical grade DCM, the acetone/ice bath was kept up, along with magnetic stirring for 24 hours.
At the end, the DCM was transparent yellow, as expected, and dried for awhile in a homemade dessicator over Calcium Chloride, I left it in the dessicator and the DCM evap'd off quickly(I lost my vacuum adaptor so couldn't distill the DCM off).

Final yield was under 1 gram of pea green crystal shards, along with some black crystals assumed to be the quinhydrone .
Can anyone spot anything wrong?
I don't know if my ice bath got to -10°C, thermometers were in the mail at the time.
HCl used was 34% (w/w) muriatic acid from the hardware store. The oxygen was from a bottle for a torch.

Because of the reagents being so cheap I'll give this a try again soon and report back. Hopefully someone has some ideas or can spot my mistakes.

Thanks
blaaky

[hypo]

you don't mention any O2?

[Mountain_Girl]

Hypo,
He said: "The oxygen was from a bottle for a torch."  

Blaaky:
You start with ~25 g of solid in the DCM, you eventually evaporate, only to get ~1 g of solid - where'd the rest go ?
You must have done some further processing that you have not detailed in your post..no ?

[blaaky]

I weighed out 25 grams of hydroquinone... and after the DCM evapped there was the small ammount of crystal in the beaker as described. I am at a loss also. Is p-benzoquinone volatile? Could the calcium chloride used as a drying agent sucked it up? I really am at a loss as to what happened.

hypo: I purged the flask with O2 via a hose from the O2 bottle and attached an O2 filled balloon as described, I used a 500mL 1-neck flask as the rxn vessel.

I will repeat the synth when I get some free time this weekend. ONE other thing... I had a lab assistant (real person) manage the ice bath during part of it. Maybe that person spilled some and added more DCM to hide it, that is a possibility, since I can't make any sense of the results.

-blaaky

[Aurelius]

how much calcium chloride did you use for the drying?   you shouldn't ever use very much at all.

[blaaky]

I'm estimating here... but I think I wrapped up maybe 15 grams  of Calcium Chloride in a paper towel. Put that in the drying chamber, the beaker with DCM/benzo solution on top and then sealed the chamber. It completely evaporated while in there. heh. I need a real dessicator

-blaaky

[hypo]

how many mol O2 per mol hydrochinone? 1?
with a mol weight of 110g/mol this gives 222mmol
or 5.3L O2, right?

the O2 flask was connected during the whole reaction, wasn't it?

(btw: dissicators are used to dry solids, _not_ solutions.)

[blaaky]

I didn't measure out the O2 at all, I just followed the synth where i purged the flask with O2, and attached a balloon filled with O2 to the neck, I didn't have to refill the balloon it stayed pretty full the entire reaction. Even if the hydroquinone wasn't oxidized, where did it go?

hypo, can you clarify in the synth what it means "dry over MgSO4" I assumed that meant to stick it in a dessicator over  MgSO4, not add the drying agent to the solution!

[Mountain_Girl]

Actually you do add the MgSO₄ to the liquid and filter it off later, after it has absorbed the water.
Dessicators are for solids like Hypo says.
Would of pointed it out earlier but didn't think it was relevant to your specific problem.

Btw, benzoquinone does sublime but not to the extent that would explain it's almost-absence.

[Aurelius]

Use should never use that much calcium chloride to dry such a small amount of mixture.  2g max for that mix.  If you solvent has more water in it than that, you needed to dry the solvent before ever beginning the procedure (recommended anyway).   all that 15g served you with was a dramatic loss of product by adsorption and absorption.  it's no wonder you're losing product.  I don't think that were it all went, but I'm sure quite a bit went the way of trash drying agent.

[blaaky]

Thanks for the suggestions, I'll report back when I try this again...

Why haven't more bee's trying this synth? I got a kilogram of sodium nitrite for $10 dollars and 500g of hexamine for $5. You can't beat the price and yields (once I am successful).

Thanks again
blaaky