Hydroquinone residue

Al-Omran and Rose controlled the location and extent of sulfonation on poly (ary lene ether) backbones by copolymerizing 4,4 -dichlorodiphenyl sul-fone, durohydroquinone, and hydroquinone to form random copolymers, where only the hydroquinone residue would be expected to be susceptible to sulfonation by sulfuric acid. Although these authors observed sulfonation at positions other than at the desired hydroquinone locations, designing sulfonation sites into a polymer backbone remains an attractive strategy for producing copolymers with known structures. This allows the chemical structure and composition of the material to dictate the extent of sulfonation rather than trying to externally control sensitive and sometimes unpredictable macromolecu-lar sulfonation reactions. 

The pyrazolotriazole (82) is an example of an oxichromic developer which has no hydroquinone residue (81BRP2061537). 

Color Photography (see Section 5.7). Chromium 1 1 complexes such as 40 [79230-32-3] [65], and 1 2 chromium complexes, both containing a hydroquinone residue as developer group, are used as photo dyes [66], Nickel complexes of 2-amino-6-arylazo-3-pyridinol dyes can also be used for photographic purposes [67],... 

Preliminary investigations suggested that it would be possible to form a related poly-pseudorotaxane built up from a linear component incorporating linked linear polyether strings. Thus, reaction of the linear component incorporating three hydroquinone residues with methylenebis(4-phenylisocyanate) yielded the... 

The reduction of pyrrolizidine alkaloids on a redox polymer containing bound hydroquinone residues has been investigated. ... 

More recently copolymers have been developed for use in fnel cell membranes. Commercial membranes are often sulfonated fluoropolymers bnt snlfonated PAEK can also have a good level of performance. Victrex has designed polymers which consist of easy-and hard-to-sulfonate blocks which make sulfonation in sulfuric acid easy to control [16]. For example a biphenol or hydroquinone residue is highly reactive to electrophiles and is easily sulfonated in concentrated sulfuric acid. In contrast phenylene groups deactivated... 

Al-Otnran, A., Rose, J.B. (1996) Synthesis and suUbnation of poly(phenylene ether ether sulfone)s containing methylated hydroquinone residues. Polymer, 37, 1735-1743. 

About 0-1 per cent, of hydroquinone should be added as a stabiliser since n-hexaldehyde exhibits a great tendency to polymerise. To obtain perfectly pure n-/iexaldehyde, treat the 21 g. of the product with a solution of 42 g. of sodium bisulphite in 125 ml. of water and shake much bisulphite derivative will separate. Steam distil the suspension of the bisulphite compound until about 50 ml. of distillate have been collected this will remove any non-aldehydic impurities together with a little aldehyde. Cool the residual aldehyde bisulphite solution to 40-50 , and add slowly a solution of 32 g. of sodium bicarbonate in 80 ml. of water, and remove the free aldehyde by steam distillation. Separate the upper layer of n-hexaldehyde, wash it with a little water, dry with anhydrous magnesium sulphate and distil the pure aldehyde passes over at 128-128-5°. 

The original recipe adopted by the U.S. Government Synthetic Rubber Program was known as the "Mutual Recipe" and is shown iu Table 4. As can be seen, the reaction temperature was set at 50°C, which resulted iu 75% conversion to polymer iu about 12 h. The reaction was then stopped by addition of a "shortstop," such as 0.1 parts hydroquinone, which destroyed any residual catalyst (persulfate), and generated quiuone, which helped inhibit any further polymerisation. 

The reaction mixture was removed from the vessel and distilled at a pressure of 30-60 mm, and a bath temperature of 30°C to 50°C until the methanol had all been removed. The extremely viscous tarry residue remaining in the still pot was given a very crude distillation, the distillate boiling at B2°C to 1 32°C/2 mm. In an attempt to purify this distillate by a more careful distillation, 5.3 g of a liquid distilling from 53°C to 150°C/5 mm was collected. At this point, much solid sublimate was noted not only in this distillate but in the condenser of the still. 7 g of the solid sublimate was scraped out of the condenser of the still. Recrystallization of the sublimate from ethyl acetate containing a small amount of petroleum ether gave beautiful crystals melting at 175°C to 177°C (5 g). Infrared analysis confirmed that this compound was hydroquinone (9% conversion). 

The reaction mixture is poured into a separatory funnel containing about 0 S kg. of crushed ice and is shaken thoroughly. The organic layer is separated, and the aqueous solution is extracted with two SO-ml. portions of methylene chloride. The combined organic solution is washed three times with 75-ml. portions of water A crystal of hydroquinone is added to the methylene chloride solution (Note 1) which is then dried over anhydrous sodium sulfate. After evaporation of the solvent, the residue is distilled to give the crude product, b p. 68-74° (0.9 mm.). After redistillation there is obtained 60-66 g. (81-89%) of mesitaldehyde b.p. 113-115° (11 mm.), 20d 1.5538. 

Catechol is also obtained from coal coking and from certain wood residues. Vanillin (synthetic vanilla flavoring) is a catechol derivative. Resorcinol and hydroquinone are currently made by the same type of chemistry used... 

Vitamin K is the cofactor for the carboxylation of glutamate residues in the post-synthetic modification of proteins to form the unusual amino acid y-carboxygluta-mate (Gla), which chelates the calcium ion. Initially, vitamin K hydroquinone is oxidized to the epoxide (Figure 45-8), which activates a glutamate residue in the protein substrate to a carbanion, that reacts non-enzymically with carbon dioxide to form y-carboxyglut-amate. Vitamin K epoxide is reduced to the quinone by a warfarin-sensitive reductase, and the quinone is reduced to the active hydroquinone by either the same warfarin-sensitive reductase or a warfarin-insensitive... 

X-ray diffraction measurements have shown that Bisphenol-AF-derived poly(aryloxydiphenylsilane) is amorphous.28 The Tg value of 106°C is higher than that of the poly(aryloxydiphenylsilane)s derived from dianilinodiphenylsilane and bisphenols such as 4,4 -biphenol, 2,7-dihydroxynaphthalene, and hydroqui-none.28 The aromatic units in poly(aryloxy-diphenylsilane(s) have a remarkable effect on the Tg. The thermal stability of this polymer is somewhat lower than those of poly(aryloxydiphenylsilane)s derived from dianilinodiphenylsilane and bisphenols such as 4,4 -biphenol, 2,7-dihydroxynaphthalene, and hydroquinone. The DT10 is 362°C and the residual weight at 500°C in air is 54%. 

Figure 11. The influence of residual H2O2 on the reaction testing of phenol hydroxylation to catechol (CAT), hydroquinone (HQ), and para-benzoquinone (BQ) [61], Reaction conditions 4 g phenol 50 mL water solvent 0.2 g a-Fe203 catalyst inner standard ethanol reaction temperature 70°C. Aliquots were sampled at different times and analyzed by (a) HPLC and (b) GC to determine the conversions of PHE (A) and yields of CAT + HQ + BQ ( ), CAT ( ), and BQ (T). Aliquots were also analyzed by (c) iodometric titration to determine the conversion of H2O2 (o). [Reproduced by permission of Elsevier from Ma, N. Ma, Z. Yue, Y. H. Gao, Z. J. Mol. Catal. A 2002, 184, 361-370.]...

To 5.7 g (0.0527 mol) of p-benzoquinone is added 10 g (approximately 0.072 mol) of tin amalgam and 50 ml of glacial acetic acid. The mixture is heated on a steam bath. After 3 minutes green crystals of quinhydrone precipitate but soon dissolve to give a Ught yellow solution. After 0.5 hour the solution is filtered, the solvent is removed in vacuo, and the residue is recrystallized from benzene-acetone to give 5.0g (88%) of hydroquinone, m.p. 169-190°. 

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