Naphthalene bromination

In 60 % aqueous acetic acid at 25 °C naphthalene brominated according to second-order kinetics286 with a rate coefficient of 0.108, i.e. 3.16 times slower than in 50 % aqueous acid, so that the change in rate with change of water content in a medium of high water content is very much smaller than in a medium of little or no water content (cf. ref. 281) as might be expected a (20-40 °C) = 16.6, log A = 9.9 and AS = = —15.3. Clearly the reduction in rate with decrease in water con-... 

Figure 5.18 Relation between the excretion rate constant ( 2) and octanol-water partition coefficient (ATd,oct) for polyhalogenated hydrocarbons chlorinated dibenzofurans O, chlorinated dibenzodioxins O, brominated biphenyls T, chlorinated naphthalenes , brominated benzenes , chlorinated biphenyls , chlorinated benzenes. [Reproduced with permission from A. Opperhuizen and D. T. H. M. Sijm, Environ. Toxicol. Chem. 9, 175 (1990). Copyright SETAC, Pensacola, FL, USA.]...

Use a 500 ml. three-necked flask equipped as in Section IV,19, but mounted on a water bath. Place 128 g. of naphthalene and 45 ml. of dry carbon tetrachloride in the flask, and 177 g. (55 ml.) of bromine in the separatory funnel. Heat the mixture to gentle boiling and run in the bromine at such a rate that little, if any, of it is carried over with the hydrogen bromide into the trap this requires about 3 hours. Warm gently, with stirring, for a further 2 hours or until the evolution of hydrogen bromide ceases. Replace the reflux condenser by a condenser set for downward distillation, stir, and distil off the carbon tetrachloride as completely as possible. Mix the residue with 8 g. of sodium... 

The presence of free bromine, and consequently the end-point, can be detected by its yellow colour, but it is better to use indicators such as methyl orange, methyl red, naphthalene black 12B, xylidine ponceau, and fuchsine. These indicators have their usual colour in acid solution, but are destroyed by the first excess of bromine. With all irreversible oxidation indicators the destruction of the indicator is often premature to a slight extent a little additional indicator is usually required near the end point. The quantity of bromate solution consumed by the indicator is exceedingly small, and the blank can be neglected for 0.02M solutions. Direct titrations with bromate solution in the presence of irreversible dyestuff indicators are usually made in hydrochloric acid solution, the concentration of which should be at least 1.5-2M. At the end of the titration some chlorine may appear by virtue of the reaction ... 

CA Registry No 2493447-2. It is prepd by bromination of 5,6-dinitro-l,2,3,4-tetrahydro-naphthalene followed by dehydrobromination (Ref 20), from 2-nitro-l-naphthylamine by the same procedure as used for the prepn of the 1,4-isomer (Ref 20)... 

Berliner et a/.284-8 have examined kinetics of bromination in aqueous acetic acid in an attempt to find the acid concentration at which the change in kinetic order principally occurs, though it follows from the earlier work that this will depend upon the aromatic reactivity. In 50 % acid the bromination of naphthalene was second-order overall284, and at constant ionic strength the rate coefficient showed a dependence on [Br-] according to equation (140)... 

The relative rates of bromination from the above and additional studies yielded the following relative rates with partial rate factors for the indicated position in parentheses. These rates were mostly obtained by extrapolation of observed rates to those expected in 50% aqueous acetic acid and therefore probably contain small errors benzene, 1.0 (1.0) biphenyl, 1.54 x 103(4-,4.34 x 103) naphthalene, 1.24 x 105(1 -, 1.84 x 10s 2-, 1.86 x 103) phenanthrene, 7.43 x I03(9—, 2.23 x 10s) f uoranthrene, 2.30 x 106(3 —,6.90x 106) chrysene,... 

This work is in its early stages, but it is already clear that a significant improvement in P-selectivity can be achieved by use of H zeolite Y as the catalyst for the bromination of naphthalene with tert-butyl hypobromite (Fig. 8) (ref. 11). It remains to be seen whether further improvements can be achieved by variation of the counterion or by variation of solvent. Such studies are currently in progress. 

Opening an unused but old commercial ampoule of the ice-cooled bromide led to eruption of the decomposed contents [1]. Similar occurrences on 2 occasions were reported later [2], though on both occasions hexabromonaphthalene was identified in the residue (suggesting contamination of the bromide by naphthalene as an additional source of internal pressure). Sulfinyl bromide is of limited stability, decomposing to sulfur, sulfur dioxide and bromine, and so should be stored under refrigeration and used as soon as possible. 

The above method has been found to be more convenient and to give considerably better yields than that described previously.1 Bromination of naphthalene in carbon tetrachloride solution has also recently been described by Blicke.2... 

Phenylnaphthalene has been prepared by the reaction of a-halonaphthalenes with mercury diphenyl3 6 or with benzene in the presence of aluminum chloride,6 and by means of the Gri-gnard synthesis, starting with either bromobenzene, cyclohexyl chloride, and a-tetralone 7 or with a-bromonaphthalene and cyclohexanone.6 8 9 Dehydrogenation of the reduced naphthalene has been accomplished by the use of sulfur,6 bromine,8 platinum black, or selenium.7 The formation of the hydrocar-... 

Even simple dienes and polyenes are difficult to classify in comparison with alkenes. Whereas bromination, oxidation and reaction with tetranitromethane (TNM) can identify the number of double bonds and their location in the molecular structure, conjugated double bonds produce very complex mixtures. Furthermore, many of the tests based on 7r-complexation can also apply for aromatic moieties. An example is the TNM 7r-complex which is yellow with benzene and orange with naphthalene and the tests are therefore non-specific. 

The medicinal importance of 2-aryltryptamines led Chu and co-workers to develop an efficient route to these compounds (130) via a Pd-catalyzed cross-coupling of protected 2-bromotryptamines 128 with arylboronic acids 129 [137]. Several Suzuki conditions were explored and only a partial listing of the arylboronic acids is shown here. In addition, boronic acids derived from naphthalene, isoquinoline, and indole were successfully coupled with 128. The C-2 bromination of the protected tryptamines was conveniently performed using pyridinium hydrobromide perbromide (70-100%). 2-Phenyl-5-(and 7-)azaindoles have been prepared via a Suzuki coupling of the corresponding 2-iodoazaindoles [19]. 

A different synthetic route involves halogenation (bromination, chlorination) of pyrene 77, which is thus converted to the tetrahalogen derivative. Oxidation with sulfuric acid to form a diperinaphthindandione with subsequent oxidation, once again in a sodium hydroxide solution [7], yields the tetra sodium salt of naphthalene tetracarboxylic acid 78 ... 

The list of suitable substituents includes acylamino groups, but especially halogen atoms such as chlorine or bromine. Halogenated derivatives are obtained from tetrahalogen phthalic anhydride or naphthalene-2,3-dicarboxylic anhydride, by... 

Monohalogenated Benzenes and Naphthalenes Trends in aromatic toxicities (Table IV) are somewhat obscured in these two series by the toxicities of the individual substituents (2). Fluorine and chlorine substituents are reasonably inert however, the bromine and iodine atoms, particularly the latter, are extremely toxic. In the case of inert substituents (F, Cl) the results resemble those of the alkylbenzenes in terms of steric hindrance to adsorption. 

The difference in the reactivity of benzylic versus aromatic halogens makes it possible to reduce the former ones preferentially. Lithium aluminum hydride replaced only the benzylic bromine by hydrogen in 2-bromomethyl-3-chloro-naphthalene (yield 75%) [540]. Sodium borohydride in diglyme reduces, as a rule, benzylic halides but not aromatic halides (except for some iodo derivatives) [505, 541]. Lithium aluminum hydride hydrogenolyzes benzyl halides and aryl bromides and iodides. Aryl chlorides and especially fluorides are quite resistant [540,542], However, in polyfluorinated aromatics, because of the very low electron density of the ring, even fluorine was replaced by hydrogen using lithium aluminum hydride [543]. 

Ph) has been reported to proceed smoothly to give, as expected, the corresponding 3-Cp-nitrophenyl) and 3-(p-bromophenyl) derivatives. Gibson found that the betaine (132, R = Me) dissolved in sulfuric acid to give a blue solution, a result which is consistent with sulfonation in the naphthalene ring system, and also reported that the same compound reacted smoothly with bromine in acetic acid to give a tetrabromo derivative in which all the bromine atoms were located in the naphthalene system. The structure of this compound was not, however, established. ... 

Sodium hydroxide. Sodium cyanide. Bromine, Sulfuric acid Sulfuric acid. Bromine, Sodium cyanide Acetone, Sulfuric acid. Bromine, Methylene chloride Biguanide, Ethanol, Perchloric acid. Ethyl acetate l,3-Dichloro-2-propanol, Trioxane, 1,2-Dichloroethane, Sulfuric acid, Sodium bicarbonate, Dimethylsulfoxide, Sodium azide. Methylene chloride Ammonium nitrate, Nitromethane Ammonium nitrate, Hydrazine Sodium nitrate, Sulfur, Charcoal Potassium nitrate, Sulfur, Charcoal Magnesium powder, Hexachlorethane, Naphthalene... 

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