Effects of Hydroxylation

Effect of Hydroxyl Radicals on Ozone Depletion. Hydroxyl radicals, formed by reaction of ( D) oxygen atoms with water or CH, can destroy ozone catalyticahy (11,32) as shown in the following reactions. 

When the OAc group was a hydroxyl, the epoxidation selectivity was not very good, presumably because of the known directing effect of hydroxyl groups in peracid epoxidations. 

Moorhouse, C.P., Halliwell, B., Grootveld, M. and Gutteridge, J.M.C. (1985). Cobalt(ll) ion as a catalyst of hydroxyl radical and possible crypto-hydroxy radical formation under physiological conditions. Differential effects of hydroxyl radical scavengers. Biochem. Biophys. Acta 843, 261-268. 

Ivanov, A.I., Fomchenkov, V.M., Khasanova, L.A., and Gavriushkin, A.V., Toxic effect of hydroxylated ions of heavy metals on the cytoplasmic membrane of bacterial cells, Mikrobiologiia, 66 (5), 588-594,1997. 

M. Clare, R. A. Mueller, and K. Houseman, Effect of hydroxyl group configuration in hydroxyethlamine dipeptide isosteres on HIV protease inhibition, J. Med. Chem. 34 1222(1991). 

Table III. Substituent Effect of Hydroxyl Groups on Carbon Chemical Shifts of Polyethers...

G115 extract protects rat heart from iechemia-reperfusion injury G115 extract protects rabbits pulmonary artery from free radical injury G115 extract inhibita dose-dependently lipid peroxidation in rats Activation of the superoxide dismutase gen by Rb2 Scavenging effect of hydroxyl radicals, protection of fatty acids Anti free radical action of Ginsenosides Rb1, Rb2, Rb3, Rc, Rd in rats Antioxidant action in rats (SOD, catalase, glutathionperoxidase)... 

Schechter 55) proposed that the catalytic effect of hydroxyl groups on the epoxide-amine addition reaction involved a termolecular activated complex formed in the concerted reaction of amine, epoxide and hydroxyl. Smith 57) suggested a modified mechanism in which the same activated complex is formed in a bimolecular reaction between an adduct formed from epoxide (E) and the proton donor (HX), and the amine ... 

Estimating the reactivity of various aromatic nuclei in lignin involves studies to determine the protodedeuteration rates of certain selectively deuterated model compounds. The combined effects of hydroxyl, methoxyl, and side-chain substituents are approximately additive in guaiacyl models while syringyl models show significant deviation from the predicted behavior. The reactivity of the position meta to methoxyl groups is higher while those of the ortho and para positions are lower than anticipated on the basis of combined substituent effects. 

Cullis PM, Langmann S, Podmore ID, Symons MCR (1990) Effects of ionizing radiation on deoxyribonucleic add. Part VI. - Effects of hydroxyl radical scavengers on radiation damage to DNA. J Chem Soc Faraday Trans 86 3267-3271... 

Liu, C., and Huang, P. M. (2000). Catalytic effects of hydroxyl-aluminum and silicic acid on catechol humification. In Humic Substances Versatile Components of Plants, Soil and Water, Ghabbour, E., and Davies, G., eds., Royal Society of Chemistry, Cambridge, UK, pp. 37-51. 

In most bioassays a 33-hydroxyl group increases bio-activity as does a 13-hydroxyl group. An exception is the cucumber hypo-cotyl assay in which 13-hydroxy GAs have lower activity than the equivalent 13-deoxy compounds. In general the most active GAs have both 33- and 13-hydroxyl groups and a 1,2 double bond or some combination of these. Interestingly, when the 33-hydroxyl group is epimerized to the 3 position bio-activity is virtually eliminated (89). The effect of hydroxylation at positions other than 33 or 13, with the exception of the 23-position, is difficult to assess because of insufficient examples. 

The effect of hydroxyl groups upon the reactions of diazonium salts with ethyl alcohol appears not to be established.28 4 > 41> ... 

The directing effects of hydroxyl groups in homogeneous hydrogenation reactions are well established but the equivalent effect is also... 

Adams and Randtke [154] and Adams et al. [181] were among the pioneers in the study of atrazine ozonation in laboratory-prepared and surface waters. These authors identified some of the ozonation by-products such as deethylatrazine, deisopropylatrazine, etc., and proposed a simplified reaction mechanism. The molecular structure of atrazine suggested that hydroxyl radical oxidation could be more effective than direct ozonation alone. Thus, the application of different advanced oxidation and photolysis technologies to eliminate atrazine was investigated in other studies [69,79, 182], Results obtained from these studies show the paramount importance of free radical oxidation as compared to direct photolysis or direct ozonation. Degradation of the herbicide was found to be much slower in the presence of t-butanol due to the scavenging effect of hydroxyl radicals. 

The effects of hydroxyl radical scavenging by methanol were predicted accurately. For more complex compounds and for high concentrations, a detailed knowledge of the reaction mechanism is necessary to obtain good agreement between empirical and modeled results. 

Metabolites of PCBs also exert biological effects. The Ah-receptor mediated responses, however, are probably caused by the parent compounds only. The effects of hydroxylated PCBs include inhibition of cytochrome P450-dependent enzyme activities and competitive interference with thyroid hormone and vitamin A metabolism.89,90 Methylsulfonyl-PCBs have been shown to inhibit aryl hydrocarbon hydroxylase activity91 and to elicit phenobarbital-type toxicity and may in fact be responsible for the observed effect presumed to be caused by the parent compound.92... 

In the presence of nitrate under irradiation, catechol yields 4-nitrocatechol and hydroxybenzoquinone. The effect of hydroxyl scavengers indicates that the formation of 4-nitrocatechol is due to nitrogen dioxide, whereas hydroxybenzoquinone forms upon reaction of catechol with hydroxyl [78,79]. 

Hussain, A. Yamasaki, M. Truelove, J. Kinetics of hydrolysis of acylals of aspirin hydrolysis of (I -ethoxy) ethyl 2-acetoxybenzoate. J. Pharm. Sci. 1974, 63, 627-628. Hussain, A. Truelove, J. Kostenbauder, H.B. Effect of hydroxyl group substituents of pyran ring on hydrolysis rate of benzoates 2-tetrahydropyranyl benzoate. J. Pharm. Sci. 1979, 68, 235-236. 

Lehner, S.J. Muller, B.W. Seydel, J.K. Effect of hydroxyl-propyl-beta-cyclodextrin on the antimicrobial action of preservatives. J. Pharm. Pharmacol. 1994, 46, 186-191. 

The effect of hydroxyl groups upon the reactions of diazpnium salts with ethyl alcohol appears not to be established. -Very recently it has been shown that treatment of the double salt of zinc chloride and p-hydroxybenzenediazonium chloride with ethyl alcohol leads to phenol (38% yield) and p, p -azophenol (ca. 50-55% yield). ... 

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