--------------------------------------------------------------------------------
      Synthesis of p-quinone, p-toluquinone, hydroquinone and toluquinone
--------------------------------------------------------------------------------


p-Benzoquinone
==============

p-Benzoquinone from hydroquinone [1]

Cool a solution of 33g of hydroquinone in 150 ml of 60% acetic acid
contained in a 600ml beaker to below 5øC in an ice bath. Dissolve 42 grans
of chromium trioxide (CrO3) in 70 ml of water, and add 30 ml of glacial
acetic acid. By means of an addition funnel, add the CrO3 solution to the
stirred hydroquinone solution at such a rate that the temperature does not
rise above 10øC; the addition takes about two hours. Filter the mixture at
once and wash the quinone several times with 10ml portion of ice cold
water. Spread 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), mp 115øC, is 21 grams, it darkens when exposed
to light.

      
p-benzoquinone from Hydroquinone (by Spiceboy)

In a 500 ml Erlenmeyer flask, place 23 grams of hydroquinone. Add 17.5ml 
93% H2SO4 *in* 250ml dH2O, with gentle warming until the hydroquinone 
dissolves completely. When it does, plunge the flask into an icebath with 
vigorous swirling, to obtain a very fine suspension of crystals.

Upon removal of the flask from the ice bath, add 35g of K2Cr207 (dissolved 
in 60 ml dH2O) in about five portions with swirling, S-L-O-W-L-Y. It'll 
take about 5-10 minutes. You may need to monitor the Rx temp to keep it at 
25 degrees or so.

In the early stage of oxidation, a precipitate separates that is a green-
blackish color, this is the so-called quinhydrone complex, and is a good 
sign. In the later stages, as the reaction completes, the color of the 
precip changes to yellow-green, almost day-glo-ish. Elapsed time; 65 min.

Cool mixture to 5 degrees. Filter crystals on a buchner. They consist of 
benzoquinone. Wash the crude crystals with a SMALL portion of ice-cold 
dH2O. This is good enough to use as is, but sublimation is a straight-
forward alternative for you purity freaks. The bright yellow crystals 
decolorize upon standing, so its probably a good idea to make this on an 
as-needed basis. Yields: about 14g or 60%+... BOOM. ZOWIE. 


p-Benzoquinone from Aniline [2]

A solution of 20g of aniline in a mixture of water (600 ml) and
concentrated sulfuric acid (160g, 80ml) is placed in a stout beaker
immersed in ice-cold water and continous stirring is begun. During the
course of an hour 20g of finely powdered potassium dichromate are added in
portions of about 1g at a time, care being taken that the temperature does
not rise above 10°C. An even better method is to add a solution of 20g of
sodium dichromate in 100 ml of water from a dropping funnel. In either case
the mixture is left in a cool spot overnight, and then a further quantity
of potassium dichromate (33g), or a solution of sodium dichromate (40g in
200 ml of water), added under conditions similar to the above. After four
or five hours the mass is extracted three times with ether, the ethereal
solution dried with calcium chloride, and the ether removed by evaporation.
The crude quinone is purified by distillation in steam, or by sublimation,
and forms orange-yellow needles with a characteristic pungent odour.
Melting-point, 116ø. Yield, 19g (82% of theory).


Toluhydroquinone
================

p-Toluquinone from o-Toluidine [2]

A solution of 20g of o-Toluidine in a mixture of water (600 ml) and
concentrated sulfuric acid (160g, 80ml) is placed in a stout beaker
immersed in ice-cold water and continous stirring is begun. During the
course of an hour 20g of finely powdered potassium dichromate are added in
portions of about 1g at a time, care being taken that the temperature does
not rise above 10°C. An even better method is to add a solution of 20g of
sodium dichromate in 100 ml of water from a dropping funnel. In either case
the mixture is left in a cool spot overnight, and then a further quantity
of potassium dichromate (33g), or a solution of sodium dichromate (40g in
200 ml of water), added under conditions similar to the above. After four
or five hours the mass is extracted three times with ether, the ethereal
solution dried with calcium chloride, and the ether removed by evaporation.
The crude quinone is purified by distillation in steam, or by sublimation,
and forms orange-yellow needles with a characteristic pungent odour.
Melting-point, 67°C. Yield, 19g (82% of theory).


Toluquinone (Method 2) [3]

Alkylated hydroquinones and p-aminophenols.

p-Alkyl nitro aromatic compds. are reduced with powd. Al and aq. acid 
(H2SO4, H3PO4, HCl, (CO2H)2, or RSO3H) to the corresponding alkyl hydroquinones; 
the alkyl chain may be up to 4 C atoms in lenght. Reduction at elevated temp. 
yields the corresponding alkyl p-aminophenols obtained in mixt. with the 
hydroquinones. Addn. of 7.5g Al flakes [Osmium bets turnings or his favorite 
sheet will work] over 1.5-2.0 hrs. at 95° to 17.5g p-O2N-C6H4-Me [p-nitrotoluene, 
leftover from Cheapskate's Quaalude synth.] in 37.5 ml. H2SO4 (d. 1.85) and 500ml. 
H2O, filtration, and steam distillation gave a little (p-MeC6H4)2NH, m.78-9°; 
extn. with Et2O gave 4.5g 1,2,5-MeC6H3(OH)2 [toluhydroquinone], m. 125° (from 
petr. ether); addition of Na2SO3 and Na2CO3 until the soln was alkaline, 
filtration, treatment with Et2O and EtOH and concentration of the organic 
extracts gave 0.65g p-toluidine, m. 44°.

A similar reaction with a smaller amt. of Al gave some p-cresol in addn. to the above 
products. p-O2N-C6H4-Et similarly gave ethylhydroquinone. Similarly, p-PrC6H4-NO2 
yields propylhydroquinone, m. 89-90C°C. p-BuC6H4-NO2 similarly yields butylhydroquinone, 
m. 86.5-87.0°C The Al flakes may be conveniently added to a mixt. of the NO2 compd.and 
aq. acid. 


Toluhydroquinone (Method 1) [1]

Dissolve or suspend 10 grams of p-toluquinone in 2M HCl, and add a little
Zinc powder. When the solution is colorless, filter, neutralize with
NaHCO3, extract the dihydric phenol with ether, and evaporate the solvent.


Toluhydroquinone (Method 2) [1]

Dissolve or suspend 10 grams of p-toluquinone in 100ml of ether and shake
vigorously with a solution of 20 grams of sodium hydrosulfite (Na2S2O4) in
200 ml of 1 M sodium hydroxide solution until the color of the quinone has
disappeared. Separate the alkaline solution of toluhydroquinone, cool it in
ice, and acidify with concentrated HCl. Collect the product (with Et2O?) and
recrystallize from water or alcohol.         


References
==========

[1] A. I. Vogel, Practical Organic Chemistry, 3rd Ed
[2] Sudborough & Campbell, Practical Organic Chemistry
[3] US Pat 2,533,20; CA 45, 3419e