4-Bromophenol, reaction with

A good technical grade of carbon tetrachloride contains not more than the following amounts of impurities 1 ppm acidity as HCl, 1 ppm carbon disulfide if manufactured by carbon disulfide chlorination, 20 ppm bromine, 200 ppm water, and 150 ppm chloroform. The residue should not exceed 10 ppm on total evaporation. The product should give no acid reaction with bromophenol blue, and the starch iodine test should indicate the absence of free chlorine. 

A method suitable for quantification of the functional class of bis(ethanol)amine antistatics, which lack UV chromophores, consists of reaction with methyl orange [53]. Atmer 163 (alkyl-diethanol amine) has been determined as a yellow complex at 415 nm after interaction with a bromophenol/cresole mixture [64]. Hilton [65] coupled extracted phenolic antioxidants with diazotised p-nitroaniline in strongly acidic medium and carried out identification on the basis of the visible absorption spectrum in alkaline solution. The antioxidant Nonox Cl in... 

The intramolecular mechanism of this reaction is proved by cross experiments for the metallation and 1,3-rearrangement reaction. In the same manner it is possible to yield the benzoxasiloles 11 (Eq.(4)). The first step in the reaction of chloromethylsilylethers of o-bromophenol 10 with sodium in boiling toluene is the metallation, followed by 1,3-rearrangement and intramolecular cyclization [8]. 

Subsequent monosilylation and Wittig reaction furnished unsymmetrical double diene 170. The synthesis of the other Diels-Alder partner started from bromophenol 173 (prepared in three steps from dimethoxytoluene), which was doubly metalated and reacted with (S,S)-menthylp-toluenesulfinate 173. CAN oxidation delivered quinone 171, which underwent a Diels-Alder reaction with double diene 170 to give compound 175 possessing the correct regio- and stereochemistry. Upon heating in toluene the desired elimination occurred followed by IMDA reaction to adduct 176, which was obtained in an excellent yield and enantioselectivity. Both Diels-Alder reactions proceeded through an endo transition state the enantioselectivity of the first cyclization is due to the chiral auxiliary, which favors an endo approach of 170 to the sterically less congested face (top face) (Scheme 27). 

DMAC does not detect urea, but uronium ion (8). Another color test for urea nitrate, which is less specific but is simple and quick, was developed in Israel by A. Bomstein. It is based on the fact that urea nitrate is highly acidic thus, the pH indicator bromophenol blue changes its color from blue to yellow upon reaction with trace amounts of urea nitrate [95]. Red pigment formation in the reaction between p-DMAC and urea nitrate [91, 92] is as follows ... 

The robust nature of the rhodium-iodide catalyst is also revealed in reactions with ortho-halo phenols that proved to be problematic with the first-generation catalyst system (Section 9.3.1). By employing the [Rh(PPF-P Bu2)I] catalyst, complete conversion is obtained with 2-bromophenol to give 6 in 94% yield, and with 95% enantiomeric excess after only 1.5 h of reaction time at 1 mol% catalyst loading (Scheme 9.3) [11]. The ready availability of these ring-opened compounds has been utilized to prepare enan-tiomerically enriched benzofurans 7. 

As well as detoxication via reaction with GSH, the reactive 3,4-epoxide can be removed by hydration to form the dihydrodiol, a reaction that is catalyzed by epoxide hydrolase (also known as epoxide hydratase). This enzyme is induced by pretreatment of animals with the polycyclic hydrocarbon 3-methylcholanthrene, as can be seen from the increased excretion of 4-bromophenyldihydrodiol (Table 7.5). This induction of a detoxication pathway offers a partial explanation for the decreased hepatotoxicity of bromobenzene observed in such animals. A further explanation, also apparent from the urinary metabolites, is the induction of the form of cytochrome P-450 that catalyzes the formation of the 2,3-epoxide. This potentially reactive metabolite readily rearranges to 2-bromophenol, and hence there is increased excretion of 2-bromophenol in these pretreated animals (Table 7.5). 

The metabolites 2- and 4-bromophenol can also be metabolized by a further oxidation pathway to yield catechols and quinones, some of which are cytotoxic and potentially hepa to toxic. Thus, in vitro studies have indicated that bromo quinones and bromocatechols may be responsible for some of the covalent binding to protein and reaction with GSH. 

In addition to being hepatotoxic, bromobenzene is also nephrotoxic because of the production of reactive polyphenolic GSH conjugates, covalent binding to protein, and the production of ROS. 2-Bromophenol and 2-bromohydroquinone are both nephrotoxic metabolites of bromobenzene. Quinones are both oxidants and electrophiles, undergoing both one and two electron reduction and reaction with sulfydryl groups such as GSH and... 

Fig. 4.47) of up to the fourth generation with terminal chloride functions [90], These could be transformed into the corresponding terminal functional groups, for example by reaction with p-phenylphenol, p-bromophenol, lithium phenyl-acetylide, or allylmagnesium bromide. 

Several reactions of aromatic compounds have been investigated for their energies of activation. These include p-bromophenol, phthalate, benzoate, henzensulphonate ions, benzyl alcohol, phenylalanine and phenyl acetate, the specific rates of which range from 3-7 x 107 to 1-2 x 1010 m—1 sec-1. The energies of activation of all these reactions were found to be the same, namely, 3-5 + 0-5 kcal mole-1 (Anbar et al., 1967). This corroborates the conclusion that the rate-determining step in e a-reactions with aromatic compounds involves one and the same process, namely, the accommodation of an electron into the aromatic substrate. The subsequent reactions discussed above may be fast or slow but are not involved in the rate-determining step of the reaction of the hydrated electron. 

This sequence explains Price s observations adequately and seems to be required in this particular case. The oxidative elimination of halide ion from salts of phenols does not always follow this course, however. In the peroxide-initiated condensation of the sodium salt of 2,6-dichloro-4-bromophenol (Reaction 23) molecular weight continues to increase with reaction time after the maximum polymer yield is obtained (Figure 5) (8). Furthermore, Hamilton and Blanchard (15) have shown that the dimer of 2,6-dimethyl-4-bromophenol (VIII, n = 2) is polymerized rapidly by the same initiators which are effective with the monomer. Obviously, polymer growth does not occur solely by addition of monomer units in either Reaction 22 or 23 some process leading to polymer—polymer coupling must also be possible. Hamilton and Blanchard explained the formation of polymer from dimer by redistribution between polymeric radicals to form monomer radicals, which then coupled with polymer, as in Reaction 11. Redistribution has indeed been shown to occur under... 

Alkyl aryl ethers. o-Brompphenols are converted into o-alkoxyphenols by reaction with an alcohol, BaO, and CuCl2 in DMF at 110 for 3 hours followed by removal of the solvents under reduced pressure. An alternative method is to treat the bromophenol with an alcohol, NaOH, CaO, and CuCl2 in DMF. Yields are in the range 85-95%. The same reactiop with a p-bromophenol gives p-alkoxyphenols in much lower yield. The reaction with 2-bromoanisole fails. ... 

Kinetics of a quite different type are observed for the reactions of Bromophenol Blue with aromatic amines. Aromatic amines are such weak bases that only the first acidic function of Bromophenol Blue is involved, and the product of the reaction is of type IV. The overall rate of formation of the ion-pair from the acid and the base is found to be many orders of magnitude less than the diffusion-controlled rate, and, for several amines, has a negative enthalpy of activation [97], These data, listed in Table 21, can be interpreted in terms of the rate-limiting step being the intramolecular conversion of the hydrogen-bonded species ROH—B to the ion-pair RO —HB+. Although the reaction consists of the... 

Rate coefficients for the reaction of Bromophenol Blue with aromatic amines at 25 °C in chlorobenzene... 

Reaction of the bromophenol (31) with KNH2 in liquid ammonia furnished 1-hydroxy-2,10-dimethoxyaporphinein 18% yield. Reactants devoid of the necessary phenolic function in ring A do not afford aporphines on treatment with the strong... 

Early y-radiolysis experiments with p-bromophenol have shown that reaction with solvated electrons yields Br ions quantitatively and that the organic products include hydroxylated biphenyl and terphenyl". From pulse radiolysis experiments it was concluded that the hydroxyphenyl radical, formed by reaction of Caq with p-bromophenol, adds rapidly (k = 1 x 10 M s ) to the parent compound (equation 6). 

The oxidation of thallium(I) with bromine occurs quantitatively in the cold. The excess of bromine is conveniently removed by reaction with phenol. The formation of a suspension of bromophenol (which interferes in the absorbance measurement) can be avoided, if the exeess of bromine is small. The aqueous glycerol solution of starch is stable and gives a good reproducibility of results. The excess of stareh does not affect the colour. The amount of the added KI should always be the same. Atmospheric oxygen slowly liberates iodine from the iodide, but the resulting increase in absorbance amounts to scarcely 7% in one hour. 

The reaction of bromophenols with tetrasulphur nitride can give one of three types of product the new ring may result from reaction with a bromine and hydroxy (see Chapter S8, Section I.S), or hydroxy and ring-carbon (Chapter 99, Section 1.7) or a mixture of the two products. For example, the table shows the products obtained from variously 4 substituted 1-naphthol. 

Similarly, reaction with, V-acetyI-2-bromoaniline gives quinolones after retro-Diels-Alder cleavage13. With 2-bromophenol and norbornadiene under similar conditions, a competitive pathway results in simple hydrocarboxylation without cleavage of the C-Br bond13. The reaction of 2-iodophenol with ethynylbenzene leads to an alkylidenebenzofuranone,3. 

The dinitriles for the preparations of (320) to (323), were best obtained from the appropriate dibromoalkane and the sodium 4-cyanophenate. In the subsequent Pinner reaction it was found that an excess of ethanol was needed to get good yields of the ethyl imidate salt and a large excess of alcoholic ammonia ensured efficient conversion to the amidine since the imidate base reacts preferably with ammonia, but any traces of the salt tend to react with solvent to give the triethyl orthoester [39(U392], 4-Bromophenol reacted with K CN in the presence of copper(II) sulphate and sodium bicarbonate to give radioactive 4-hydroxybenzonitrile which was converted by the above procedure to pentamidine labelled at the... 

D. Chen and K. J. Laidler Can. J. Chem., 37,599 (1959) studied the reaction of the quinoid form of bromophenol blue with hydroxide ions to give the carbinol form of the dye. The following values of the second-order rate constant at 25° C were reported. 

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