Dihydroxybenzene isomers

Rincdn, A.G., Pulgarin, C., Adler, N. and Peringer, P. (2001) Interaction between E. coli inactivation and DBP-precursors - dihydroxybenzene isomers - in the photocatalytic process of drinking-water disinfection with Ti02. J. Photochem. Photobiol. A Chem. 139, 233-241. 

It is well-known that diaminobenzene (DAB) and dihydroxybenzene isomers form polymer films on an electrode surface when oxidized. Six monomers were used, either by themselves, or in combination to form the electropolymerized films 1,2- 1,3- and 1, J(-Diaminobenzene 1,2-dihydroxybenzene (iitechol) ... 

Tetrakis(4-hydroxyphenyl)porphyrin/carbon nanotubes film was able to rapidly and simultaneously detect dihydroxybenzene isomers, taking advantage of their different oxidation potentials [223]. 

Canevari, T.C., Raymundo-Pereira, P.A., Landers, R., and Machado, SA.S. (2013) Direct synthesis of Ag nanoparticles incorporated on a mesoporous hybrid material as a sensitive sensor for the simultaneous determination of dihydroxybenzenes isomers. Eur. J. Inorg. Chem., (33), 5746-5754. 

Bai J, Gno L, Ndamanisha JC, Qi B (2009) Electrochemical properties and simnltaneons determination of dihydroxybenzene isomers at ordered mesoporous carbon-modified electrode. J Appl Electrochem 39 2497-2503... 

Dihydroxybenzene (hydroquinone), and probably also the 1,2-isomer, act as reducing agents for arenediazonium ions arylhydrazines are formed, but not in good yields. The azo coupling of 2-hydroxy-l,4-benzoquinone is discussed in Section 10.10 (Scheme 10-71). 

In this paper we present the relative energies of the isomers of the phenylenediamines, dihydroxybenzenes and difluorobenzenes from ab initio calculations using large basis sets and including correlation corrections at the MP-2 level. These calculations were done at the geometry optimized structures. We also include zero-point energy corrections based on our calculated force fields. 

A variety of electronic effects control the relative energies of the disubstituted benzenes. For the difluorobenzenes, the meta and para isomers are of comparable energy the ortho isomer is clearly less stable. This is most likely due to the electrostatic repulsions of the two C-F bond dipoles which are aligned in the same direction. This is just like the difluoroethylenes where the 1,2-cis isomer is much less stable than the 1,1-isomer.poj. he dihydroxybenzenes. 

This conclusion is supported by results of detailed study on the decay of hydroxyhexa-dienylperoxyl radicals, formed by addition of OH to benzene, followed by addition of dioxygen molecule. It was found that in the high dose rate of pulse radiolysis, hydro-quinone is the major product whereas catechol was not observed, indicating that only the 1,3-isomer loses HO2" and hence does not lead to dihydroxybenzene. The observation that the yield of 02 is 60% of the yield of the cyclohexadienyl radicals indicates that when dioxygen molecules react with the cyclohexadienyl radical, the radical is 60% trapped in the mesomeric form of 5b, whereas the results from the final products of dimerization in /-radiolysis show that 60% react in the form 5a. 

Zymalkowski and Strippel hydrogenated dihydroxybenzenes with only slight hydrogenolysis over rhodium-platinum oxide in acetic acid at room temperature and 10 MPa H2 and obtained the corresponding cyclohexanediols in 92-96% yields (eq. 11.17).97 The hydrogenations at atmospheric pressure required much longer reaction times, and the yield of cyclohexanediol decreased to 86% with resorcinol. The proportions of cis isomer in the cyclohexanediols obtained at 10 MPa H2 were 81% from catechol, 68% from resorcinol, and 68% from hydroquinone and always greater than those obtained at atmospheric pressure (75,49, and 52%, respectively). 

Solubility. According to our classification system, all intra-molecular bonded materials should be Class AB. Consequently, they should be soluble in solvents from Classes AB, B, and A, provided the solvent can successfully compete with the internal H bonding. Because of the internal satisfaction of the H bonding tendency. Class N solvents should be better solvents for internally H bonded materials than for nonchelated compounds. This is the behavior observed, as shown in Table 5-V for dihydroxybenzenes in CCh. In the stronger acid and base solvents, the loss of chelation is suggested. Further, for this case, the table shows a similarity in the solubilities of ortho and meta isomers. 

As sample values of viscosity, compare the data in Table 5-XI. Notice the substituted anilines. Here, even though an tn/ramolecular H bond may form in the ortho isomer, the second amino hydrogen gives intermolecular association, and ortho- and/>ara-chloroaniline have similar viscosities. Both values are larger than that shown for the nonassociated o-chlorotoluene. Dihydroxybenzenes and derivatives provide similar data (721) as do nitroanilines, zdthough these compounds are further complicated by intermolecular H bonding. They show mixed association. ... 

An autoxidative procedure has been described by the initial alkylation of phenol with cyclopentadiene in the presence of phosphoric add at ambient temperature giving 4-(cyclopenten-2-yl)phenol, in more than 80% yield followed by isomerisation in 91% yield to the 1-isomer during 2 hours in refluxing benzene solution with a catalytic quantity of dichlorobis(benzonitrile)palladium(ll). The conjugated product with 30% hydrogen peroxide and hydrochloric add upon stirring at 50°C for 3 hours afforded 1,4-dihydroxybenzene in 92% yield accompanied by cyclopentanone (ref.46). 

Phenol is oxidised by H2O2 to hydroquinone (/ -dihydroxybenzene) and catechol (o-dihydroxybenzene) over TS-1 in aqueous or mixed aqueous/organic solutions (Scheme 9.1). Both isomers are formed, with an o-jp-raXio of 0.5 to 1.3, depending on the conditions. No hydroxylation occurs at the meto-position (Scheme 9.3). 

An enantioselective Stetter employing a chiral NHC and Hunig s base (EtNPr-j ) in methanol at 0°C has its yield massively boosted by addition of 1 equiv of catechol (1,2-dihydroxybenzene), whereas other phenols such as isomers of catechol or its monomethyl ether have negligible effect. Studies of deuterium kinetic isotope effects suggest that initial proton transfer from catechol (97) to form the aryl anion equivalent (98) is turnover limiting. Intramolecular examples are also described, requiring subpercentage amounts of NHC, base, and catechol. 

Bowen [148] obtained crystalline acrylic monomers, thus making it possible to purify them. By the reaction of 2-hydroxyethyl methacrylate with the three isomers of benzene dicarboxylic acid—phthalic, isophthalic, and terephthalic acid—adequate esters are obtained mixed in various proportions, these make an eutectic ternary mixture that can play the role of the organic phase in DARs. The only shortcoming of these monomers is that they show a tendency to acquire color in the presence of the polymerization accelerators (N,N-dimethyl-p-toluidine). Isomer dimethacrylates (o-, m-, and p-)bis(hydroxyethyl)-dihydroxybenzen-... 

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