10-30-02 20:47
No 374595
Method 1:
Cool a solution of 33 g (0.33 mol) of hydroquinone in 150 ml of 60 % acetic acid contained in a 600 ml beaker to below 5 °C in an ice bath. Dissolve 42 g (0.42 mol) of chromium trioxide (CAUTION !!!) in 70 ml of water, and add 30 ml of glacial acetic acid. By means of a separatory funnel with bent stem and supported over the beaker, add the chromium trioxide solution to the mechanically stirred hydroquinone solution at such a rate that the temperature does noot rise above 10 °C; the addition takes 2 hours. Filter the mixture at once and wash the quinone several times with 10 ml portions of ice cold water. Spreadd the material upon filter paper until dry but no longer or the quinone will be lost through sublimation. The yield of quinone (a bright yellow crystalline solid) is 21 g (66 %), M.P.: 115 °C. It darkens when exposed to light.
Impure quinone may be purified by placing it in a distilling flask attached to a condenser and passing a rapid steam into the flask: the quinone sublimes and collects in the receiver. It is separated from the water by filtration and dried; the M.P. is 116 °C. The vapour has a penetrating odour and attacks the eyes.
This procedure may be usefull if you are going for a Wacker oxidation.
../rhodium /wacker.
What we are looking at is good and evil, right and wrong.
(Chief Bee)
10-30-02 21:09
No 374617
It's the same as the first method in ../rhodium /quinone
(Hive Bee)
10-30-02 21:37
No 374635
(Rated as: excellent)
Yes, you can find it at page 1025 in the 5th edition. There 's even a beter method (using V2O5, which I am going to type now. It 's a shame that those chromium and vanadium oxides are so toxic & carcinogenic (CrO3 is a carcinogen, don't know about the V2O5)
...Method 2:
In a 1-litre round-bottomed flask, provided with a mechanical stirrer, place 0.5 g of vanadium pentoxide (catalyst), 500 ml of 2 % sulphuric acid, 55 g (0.5 mol) of hydroquinone and 30 g of sodium chlorate. Stir the mixture vigorously for about 4 hours. Greenish-black quinhydrone is first formed and this is converted into yellow quinone; the temperature of the mixture rises to about 40 °C (do not allow it to exceed this temperature). Cool the flask in running water, filter the mixture at the pump and wash it with 50 ml of cold water. Dry the quinone upon filter paper in the air (see Method 1) or in a dessicator over anhydrous calcium chloride. The yield is 45 g (83 %); M.P.: 111 - 112 °C. The crude quinone may be purified by steam distillation as in Method 1, or by recrystallisation from boiling light petroleum, B.P.: 100 - 120 °C (12 ml per gram): the resulting pure, bright yellow quinone has a M.P.: 115 °C and recovery is about 95 %.
What we are looking at is good and evil, right and wrong.
(Master Whacker)
10-30-02 22:51
No 374680
The V2O5 catalyzed method Cyrax quoted was used several times back in the day when I was still "feeling out" the different wackers. The yields are nearly perfect and the V2O5 catalyst is basically non-toxic. The other reagents are also OTC (an alkali chlorate and H2SO4). Perhaps the H2O2 oxidation is better as far as availablility of reagents OTC is concerned, but the vanadium pentoxide oxidation has the highest yields-PERIOD!!!
(Stranger)
10-30-02 23:28
No 374694
See also this ref: J Am chem soc april 1936 p 646-7 vol 58
It's the same synth at double quantity (but with a different work up to increase the yield to 90%)+ discussion for others substituted Hydroquinones which are obtained in high yield too.
(Chief Bee)
10-30-02 23:41
No 374696
(Rated as: excellent)
Oxidation of Hydroquinone - JACS 58, 646-647 (1936)
110g (1 mole) of hydroquinone, 60g (0.56 mole) of sodium chlorate and 0.5g of vanadium pentoxide were placed in a 2-liter flask with 1 liter of 2% sulfuric acid. The mixture was stirred by means of an electric motor for four hours, at the end of which time the hydroquinone had been completely converted to light yellow quinone. Because the temperature of the mixture rose to about 40°C during the course of the reaction the flask was cooled in an ice mixture. The yellow solid was brought upon a filter, washed with 100 cc. of cold water and dried in a desiccator over calcium chloride yielding 90g of light yellow quinone melting at 110-112°C. Extraction of the combined filtrate and washings with four 100 ml portions of benzene gave an additional 14g of quinone. On recrystallization from ligroin (bp 90-120°C) a 90% yield (97g) of pure quinone melting at 111-113°C was obtained.
(Hive Bee)
10-31-02 00:33
No 374709
Nice
.Well, I don't have experience with vanadium compounds ... and probably those dudes from the Health and Safety Executive in the UK are just pussies. They published some recommended limits (RL) which represent good practice and realistic levels for the degree of exposure. They say the recommended limit for vanadium pentoxide is 0.5 mg / m3 (for comparison: the RL for diazomethane is 0.4 mg / m3).
But since V2O5 is a crystalline compound, there is no real danger to get some dust of that compound in your lungs. I 'd be more cautious with diazomethane.
In each case, a catalytic amount of V2O5 is FAR better than 42 grams of chromium trioxide.
Ritter, great to hear that you 've good results with the vanadium catalysed reaction. I 'm
to see that a experienced bee values this procedure so much. Voilà, the JACS procedure Chimimanie found is nice supplement for that quinones.html file of yours, Rhodium.Chimimanie, now I have an opportunity to welcome you at The Hive. I like your posts very much. Keep up the good work
.
10-31-02 01:18
(Rated as: redundant)
(Chief Bee)
10-31-02 01:24
No 374724
Lab_bitch: If you had spent 10% of the energy expedited to make your besserwisser comment on scrolling instead, you would have found this fact already mentioned in this thread, as well as a link to the procedure in question.
(Stranger)
10-31-02 01:44
No 374729
I tryed it (the one from j org chem 54 3 1989 729) two times
(iodine in water soltn with HQ, add h2so4, h2o2 dropwise, let it stir at rt) but It stopped at the quinhydrone stage (the green metallics 'sparklies') and i haven't got that bright yellow BQ (in fact I got a few little crystals that sublimed when I warmed the soltn).
Although I haven't tryed it in IPA Post 359055 (Psalty: "When it's this easy, why bother fucking around ...", Law and Order)from what i heard on the hive it doesn't look too much promising, with even some people which say that the green metallics sparklies are the BQ!
holy shit no, they aren't, BQ is yellow, like 2,6 dimethyl quinone which is yellow too and the others quinones.
In conlusion I think I will try this Vanadium method which I think is simply better.
(Hive Bee)
10-31-02 01:53
No 374735
As it is On Rhodium's page, and I don't know about benzoquinone being yellow I've seen Green benzoquinone.
Also did you try modifying the procedure any maybee to see if applying some heat would help things along?
Sometimes procedures have to be modified a little to get them to work.
And by the way thanks for those referneces.
(Stranger)
10-31-02 06:11
No 374819
Quinone is YELLOW
Quinhydrone is dark GREEN
you haven't see any BQ yet. Try the V2O5 method and you may see some soon.
Cyrax: thank you for this greeting, i will try to keep this up, but I can't promise...
One day someone must post some picture of quinone/quinhydrone on thehive for the heretics...
(Master Whacker)
10-31-02 07:23
No 374844
For some reason I cant extract the direct URL to this Quinone synth from Org Syn, but here's the ref:
Organic Syntheses, CV 2, 553
Go to http://www.orgsyn.org and search for that page and the most beautiful Benzoquinone(Quinone) procedure available (IMHO) appears. The org syn procedure explains the color changes and all the other details. Yield is at least 95%!
(Hive Bee)
10-31-02 17:20
No 375015
http://www.orgsyn.org/orgsyn/prep.asp?pr
http://www.orgsyn.org/orgsyn/prep.asp?pr
http://www.orgsyn.org/orgsyn/prep.asp?pr
(Hive Bee)
11-02-02 10:10
No 375678
How about Fremy's salt?
http://www.cem.msu.edu/~reusch/VirtualTe
Ave Hive, synthetisandi te salutant!
(Chief Bee)
11-02-02 19:22
No 375759
Checked the price of Fremy's salt recently?
(Hive Bee)
11-02-02 19:30
No 375768
Checked the price of Fremy's salt recently?
No, actually I didn't. I never performed the said synthesis, but I do know from college that Fremy's salt was used to explain the hydroquinon -> quinon oxidation. Yields must have been around 70%, if I recall the details exactly.
Ave Hive, synthetisandi te salutant!
(Chief Bee)
11-02-02 19:33
No 375770
25g is €150 from Acros...
(Hive Bee)
11-02-02 19:59
No 375781
http://www.orgsyn.org/orgsyn/prep.asp?pr
http://www.orgsyn.org/orgsyn/prep.asp?pr
Ave Hive, synthetisandi te salutant!
(Chief Bee)
06-16-04 01:19
No 513662
(Rated as: excellent)
Benzoquinones and Related Compounds. Part 3.
Preparation of 1,4-Benzoquinones by Oxidation of Hydroquinones with Manganese Dioxide
J. Malcolm Bruce, Steven Fitzjohn and Ramchand T. Pardasani
J. Chem. Research (S). 252–253 (1981) (../rhodium/pdf /hydroquinone
We now report that manganese dioxide is a convenient and cheap oxidant for the preparation of 1,4-benzoquinones from their hydroquinones.
The hydroquinones, in dry benzene, were oxidised by shaking with an excess of manganese dioxide. Activated material was inferior to commercial precipitated manganese dioxide in terms of quantity required. reaction time. and ease of work-up (filtration). Several different batches were used: all gave reproducible results (see table).
Experimental
Benzene, dried azeotropically, was the solvent of choice (but toluene can be used as well). Commercial precipitated manganese dioxide was used in ~15 mol excess. Oxidation was complete after 15–30 min shaking at room temperature.
General Procedure: 2-Methoxycarbonyl-5-methyl-1,4-benzoquin
A mixture of methyl 2,5-dihydroxy-4-methylbenzoate (2.49 g), precipitated manganese dioxide (18 g), anhydrous sodium sulphate (6 g). and dry benzene (35 ml) was shaken mechanically at room temperature for 15 min. The suspension was filtered (Celite). and the filter cake was washed with dichloromethane (5x5 ml). Removal of the solvent from the combined filtrate and washings gave an oil which solidified: the orange-red quinone (2.23 g, 90%) had mp 36-38°C.
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