P-Hydroquinone

Xun L, E Topp, CS Orser (1992c) Purification and characterization of a tetrachloro-p-hydroquinone reductive dehalogenase from a Flavobacterium sp. J Bacterial 174 8003-8007. 

Lee J-Y, L Xun (1997) Purification and characterization of 2,6-dichloro-p-hydroquinone chlorohydrolase from Flavobacterium sp. strain ATCC 39723. J Bacterial 179 1521-1524. 

Xun L, J Bohuslavek, M Vai (1999) Characterization of 2,6-dichloro-p-hydroquinone 1,2-dioxygenase (PcpA) of Sphingomonas chlorophenolica ATCC 39723. Biochem Biophys Res Commun 266 322-325. 

Magnesium-hydroxyl interactions have been used in the same way with a p-hydroquinone unit attached at the meso position of a magnesium porphyrin (103). Again, the evidence for oligomerization comes from 1H NMR spectroscopy, and the results can equally be interpreted as dimerization rather than polymerization. 

Synonyms AI3-00072 Arctuvin p-Benzenediol 1,4-Benzenediol Benzohydroquinone Benzoquinol Black and white bleaching cream BRN 0605970 CCRIS 714 Dihydroxybenzene jO-Dlhydroxybenzene 1,4-Dihydroxybenzene p-Dioxobenzene EINECS 204-617-8 Eldopaque Eldoquin HQ Hydroquinol Hydroquinole a-Hydroquinone p-Hydroquinone 4-Hydroxy-phenol p-Hydroxyphenol NC1-C55834 NSC 9247 Quinol p-Quinol Quinone Tecquinol Tenox HQ Tequinol UN 2662 USAF EK-356. 

Naphthol and p-hydroquinone were smoothly trifluoromethylated with 39 in the presence of 4-(dimethylamino)pyridine or pyridine (Eqs. 25, 26) as an acid trap. 

Artifacts can also arise from reaction of the sorbent with components of the airstream, such as 03 and N02. For example, Clausen and Wolkoff (1997) observed a number of products from the reactions of 03 with Tenax, such as acetophenone, decanal, and benozic acid. Interestingly, 2,6-diphenyl-p-hydroquinone was generated when limonene was also present and was suggested to arise from the reaction with the Tenax of the radicals or the Criegee biradical generated in the ozone-limonene reaction. They also observed reactions of NOz with the Tenax sorbent. 

Oxidation-sensitive functionalities other than alcohols are remarkably resistant to the action of the TFAA-mediated Moffatt oxidation. Functional groups resistant to this oxidation include p-methoxybenzyl ethers133 and esters,143 sulfides,143a 144 thioacetals,145 nitrogen heterocycles146 and most peculiarly even selenides,147 and p-hydroquinones.148... 

P-hydroquinone lattice cavity with methylisocyanide guest. 

Table 18. Oxidation of ascorbic acid, homogentisic acid and p-hydroquinone by poly(L-Iysine)-Cu(II) complex...

The oxidation of phenol with potassium persulfate (K2S2O8) in an alkaline medium to p-hydroquinone is known as the Elbs persulfate oxidation. Elbs used ammonium persulfate for the oxidation of 2-nitrophenol (7.42) to 2-nitro-p-hydroquinone (7.43), but the potassium salt is commonly used for the hydroxylation of phenols. 

Mechanism The nucleophilic attack of phenoxide through para position of the aromatic ring carbon on the peroxide oxygen of the peroxydisulfate ion forms the intermediate persulfate 7.44. Hydrolysis of 7.44 gives the p-hydroquinone 7.30. 

Oxidation of catechols. In accordance with earlier reports, diphenyl selenoxide selectively oxidizes o- and p-hydroquinones and has no efiect on simple phenols. An example is the oxidation of 3,5-di-f-butyIcatechol in methanol at 0° to the corresponding o-quinone, possibly via a selenurane (a) (equation I). 

---