Naphthalene bromine reaction

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 ... 

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 resonance energies of fused systems increase as the number of principal canonical forms increases, as predicted by rule 6 (p. 35).75 Thus, for benzene, naphthalene, anthracene, and phenanthrene, for which we can draw, respectively, two, three, four, and five principal canonical forms, the resonance energies are, respectively, 36, 61, 84, and 92 kcal/mol (152, 255, 351, and 385 kJ/mol), calculated from heat-of-combustion data.76 Note that when phenanthrene, which has a total resonance energy of 92 kcal/mol (385 kJ/mol), loses the 9,10 bond by attack of a reagent such as ozone or bromine, two complete benzene rings remain, each with 36 kcal/mol (152 kJ/mol) that would be lost if benzene was similarly attacked. The fact that anthracene undergoes many reactions across the 9,10 positions can... 

The products ArCF2SMe are assumed to be precursors of ArCF3. Indeed, l-(tri-fluoromethyl)naphthalene is obtained in 83% yield by the reaction of l-[difluoro(methylsul-fanyl)mcthyl]naphthalene with tetrabutylammonium dihydrogen trifluoride/ l,3-dibromo-5,5-dimethylhydantoin. It should be noted that under the oxidative desulfurization conditions the electron-rich aromatic compounds can undergo ring bromination. 

Cyclohexadienol was prepared by Rickborn in 1970 from reaction of the epoxide of 1,4-cyclohexadiene with methyl lithium.100 A hydrate of naphthalene, 1-hydroxy-1,2-dihydro-naphthalene was prepared by Bamberger in 1895 by allylic bromination of O-acylated tetralol (1-hydroxy-l,2,3,4-tetrahydronaphthalene) followed by reaction with base.101 Hydrates of naphthalene and other polycylic aromatics are also available from oxidative fermentation of dihydroaromatic molecules, which occurs particularly efficiently with a mutant strain (UV4) of Pseudomonas putida.102,103 The hydrates are alcohols and they undergo acid-catalyzed dehydration to form the aromatic molecule by the same mechanism as other alcohols, except that the thermodynamic driving force provided by the aromatic product makes deprotonation of the carbocation (arenonium ion) a fast reaction, so that in contrast to simple alcohols, formation of the carbocation is rate-determining (Scheme 6).104,105... 

The importance of the steric effect accounts for the spread of the data for lf-N in the substitution reactions. Nitration and non-catalytic chlorination, reactions of modest steric requirements, define points which fall above the arbitrary reference line. Bromination, a reaction of somewhat greater steric requirements, is not accelerated to the extent anticipated on the basis of the results for nitration or chlorination. The benzoylation reaction with large steric requirements is two orders of magnitude slower than the equally selective chlorination reaction. The unusually small ratio for lf-N/2f-N for the acylation reaction is a further indication of the steric effects. Apparently, the direct substitution reactions of naphthalene respond to the retarding steric influence of the peri hydrogen in much the same way as for other ortho substituents. 

Reactions of 1,4-dimethoxynaphthalene and its 2-chloro, 2-bromo, and 2-(1,3-dioxolanyl) derivatives with BAIB/TMSX (X = C1, Br) combinations in dichloromethane result in acetoxylation, monohalogenation, or dihalogenation of the more activated ring (Scheme 26) [79]. Specific outcomes depend on the naphthalene derivative and reaction conditions. It is interesting that the 2-(1,3-dioxolanyl) derivative undergoes ipso-bromination with BAIB/TMSBr, and that this mode of reactivity was not observed with 2-(l,3-dioxolanyl)-l,4-di-methoxybenzene. These reactions are mechanistically diverse. Evidence was presented that bromination occurs after the formation of molecular bromine, and that chlorination probably follows a radical pathway involving the homo-... 

There are principally two different approaches of correlating experimental rate data of electrophilic substitution with reactivity indices (1) Correlating the index with the rate data of a given reaction, e.g. bromination. For example, a satisfying correlation of Dewar reactivity numbers with the log of rate constants of the bromination of benzene, naphthalene (1- and 2-position), biphenyl (4-position), phenanthrene (9-position), and anthracene (9-position) has been observed [55]. In correlations of this type the reactivity index corresponds to the reactivity constant in the Hammett equation while the slope of the linear correlation corresponds to the reaction constant (see also Sect. 3) (2) correlating the index with experimental a values. 

Diarylvinylidenecyclopropanes undergo a novel ring-opening reaction on treatment with iodine or bromine to give the corresponding iodinated or brominated naphthalene derivatives (Scheme 55).89... 

There is neither a partial positive nor a partial negative charge on the two nonequivalent positions 1 and 2 of naphthalene, which are poised for electrophilic substitution. One might consequently predict that electrophiles react with naphthalene without regiocontrol. Furthermore, this should occur with the same reaction rate with which benzene reacts. Both predictions contradict the experimental results For example, naphthalene is brominated with a 99 1 selectivity in the 1-position in comparison to the 2-position. The bromination at Cl takes place 12,000 times faster and the bromination at C2 120 times faster than the bromination of benzene. 

The method is essentially that of Merling and Jacobi.6 140 g of allyl alcohol, CHa. CHCHaOH, are cooled in ice-water. A stream of hydrobromic acid, which may be conveniently generated by dropping bromine on naphthalene and passing the vapors through several bottles containing naphthalene, is then passed in until the liquid is saturated, after which it is boiled under a reflux condenser for one hour, the reaction being ... 

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