Bromobenzene, conversion into

Bromobenzenes are converted into the corresponding chloro compounds on reaction with aqueous sodium hypochlorite in the presence of tetra-n-buty lammoni um hydrogen sulphate [40]. The reaction is pH dependent. At pH > 10, the bromobenzenes are effectively inert, but over the pH range 7.5-9, conversion occurs into the chlorobenzenes without any side reactions and the reaction appears to be light-induced. At more acidic levels (pH 4-5), bromobenzene is converted quantitatively into chlorobenzene within one hour. No reaction occurs in the absence of the catalyst and yields from light and dark reactions are comparable. Side reactions are observed, however, with substituted bromobenzenes under these low pH conditions. 

Cognate preparation. 3,3,5-Trimetkyl-l-methylenecyclohexane. Prepare an ethereal solution of phenyllithium by the procedure described in Expt 8.32, using 2.7 g (0.39 mol) of lithium shavings, 26 g (17.5 ml, 0.16 mol) of dry redistilled bromobenzene and 85 ml of anhydrous ether. After the conversion to phenyllithium is complete dilute the solution with a 15 ml portion of anhydrous ether and decant the solution from any unreacted lithium [Expt 8.32 Note (2)] into a clean three-necked 250-ml flask equipped with a nitro-... 

An interesting, alternative procedure, applicable at least to the removal of phenylboronic acid, involves its conversion, by treatment with bromine-water, into bromobenzene and boric acid, and the removal of these by distillation—the latter as its trimethyl ester.43... 

Outline a laboratory method for the conversion of bromobenzene into each of the following, using any needed aliphatic and inorganic reagents. 

The conversion of 3-chlorofluorobenzene into 3-bromofluorobenzene increased when the partial pressure of the former increased (Figure 3). Its conversion decreased when the partial pressure of biomobenzene increased (Figure 4). This corresponded to kinetic orders of 1 with respect to 3-chlorofluorobenzene and of -1 with respect to bromobenzene. The same experiments carried out for the reverse reaction led to kinetic orders of 0 with respect to 3-bromofluorobenzene and of O.S with respect to chlorobenzene. 

As previously pointed out, till now few works have been done in the field of arylation using nickel or palladium systems (refs. 5, 7). Only one detailed study (ref. 7) concerns the arylation of amines by haloarenes using nickel (0) or nickel (II) complexes as catalysts with bromobenzene, ammonia does not react and usually the arylation yields (indeed the GC-conversion rates of a tenfold excess of amine into arylamine) are rather low (12-38 %), even if the best results mentionned for dimethylamine and piperidine reach 57-85 % yield. 

It is difficult to replace aromatically bound halogen by a hydroxyl group. Hydrolysis of halobenzenes has been effected under pressure in the presence of alkali or after addition of catalytically active substances.526 There are numerous patents describing, e.g., the conversion of chlorobenzene into phenol 527 and phenols have been obtained from bromobenzene derivatives in an autoclave in the presence of copper catalysts.528 Hydrolysis of halo-benzene derivatives is easier if they contain electron-attracting substituents in the ortho- or /wra-position to the halogen. 

Investigations of a variety of zeoHtes by Djakovitch et al. showed that the shuc-ture or the Si/Al ratio had little influence on the activity of the catalyst. All catalysts achieved complete conversions of bromobenzenes in 20 h with 0.2 mol% Pd at 140 °C [147]. However, kinetic experiments showed that monomeric Pd complexes (in particular [Pd(NH3)4] ) incorporated into the zeolite cages have reaction rates orders of magnitude higher than Pd particles. The immobilized complex converts the aryl halides within a few minutes. Recycling experiments showed that the... 

Of considerable synthetic utility is the LDA-induced conversion of bromobenzenes into benzynes. Thus low-temperature deprotonation of m-alkoxyaryl bromides followed by warming to rt in the presence of furan gives cycloadducts (eq 46) the lithio species may also be trapped with CO2 at —78 °C to give unusual aromatic substitution patterns. Treatment of aryl triflates with LDA leads to A. A -isopropylanilines in good yield (67-98%). ... 

Discuss the differences observed in the IR and NMR spectra of bromobenzene and benzoic acid that are consistent with the conversion of bromobenzene into benzoic acid in this experiment. 

Now let s draw the forward scheme. Benzene is converted into bromobenzene upon treatment with Br2 and AlBrj (via an electrophilic aromatic substitution reaction). Bromobenzene is subsequently converted into phenyl magnesium bromide, which is then treated with carbon dioxide, followed by an acidic workup, to give benzoic acid. Conversion to the acid chloride, followed by reaction with dimethylamine, yields the desired amide. 

Benzene can be converted into chlorobenzene or bromobenzene by treating benzene with either CI2 or Br2 in the presence of an appropriate catalyst. The chemical equations for these conversions are shown below ... 

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