Chlorobenzenes, reaction

Ammonia decomposes on zeolites (9), and the effect of this decomposition on the chlorobenzene reaction may be important. Thus, the activity of CuY zeolite for ammonia decomposition was studied. Helium was used as a carrier gas, 1 ml of ammonia was injected, and the extent of ammonia decomposition was determined as a function of temperature. The decomposition was 2.4% at 350°C, 7.8% at 450° C, and 24% at 550° C. The apparent activation energy of ammonia decomposition was estimated at 13 kcal/mole. The activation energy of ammonia decomposition is close to that of benzene formation from chlorobenzene and ammonia. Thus, benzene formation results from the reaction of chlorobenzene and hydrogen formed by the decomposition of ammonia. 

With this situation in mind, the formation constant (ft) of the first ammonia molecule making the coordination bond with metal cations was taken as the measure of the ease of ammonia adsorption on metals. The values of (ft) were taken from Ringbom s table (H). The plot of the catalytic activity against formation constants of ammine complexes is shown in Figure 2. The correlation is good except for CdY. Again, the metals with lower formation constant (Na+, Ca+, Mg2+) have no activity for chlorobenzene reaction. 

The first step in this sequence is the hydroxyl radical attack on chlorobenzene (reaction 2), which likely results in the formation of chlorohydroxycy-clohexadienyl (C1HCD) radical I (Dorfman et al., 1962). This may initiate one of several possible further reactions. In the absence of strong oxidants, two predominant reactions are dimerization, to produce dichlorobiphenyls (reaction 3), and bimolecular disproportionation, to produce chlorophenol and chlorobenzene (reaction 4). Both reactions showed the stoichiometry of 2 mol... 

The Bose research group has developed a large variety of [2+2] cycloaddition reactions of ketenes with imines to form yS-lactams [16, 112, 113]. In 1991, Bose et al. described the synthesis of a-vinyl yS-lactams by [2-p2] cydoaddition of a,p-unsaturated acyl chlorides with a SchifF base in chlorobenzene. Reaction times were reduced from several hours with conventional methods to 5 min under the action of microwaves [112], and yields of the desired adducts were improved from very low to approximately 70% when compared with classical methods. 

Obtained synthetically by one of the following processes fusion of sodium ben-zenesulphonate with NaOH to give sodium phenate hydrolysis of chlorobenzene by dilute NaOH at 400 C and 300atm. to give sodium phenate (Dow process) catalytic vapour-phase reaction of steam and chlorobenzene at 500°C (Raschig process) direct oxidation of cumene (isopropylbenzene) to the hydroperoxide, followed by acid cleavage lo propanone and phenol catalytic liquid-phase oxidation of toluene to benzoic acid and then phenol. Where the phenate is formed, phenol is liberated by acidification. 

The commercial product, m.p. 53-55°, may be used. Alternatively the methyl -naphthyl ketone may be prepared from naphthalene as described in Section IV,136. The Friedel - Crafts reaction in nitrobenzene solution yields about 90 per cent, of the p-ketone and 10 per cent, of the a-ketone in carbon disulphide solution at — 15°, the proportions ore 65 per cent, of the a- and 35 per cent, of the p-isomer. With chlorobenzene ns the reaction medium, a high proportion of the a-ketone is also formed. Separation of the liquid a-isomer from the solid p-isomer in Such mixtures (which remain liquid at the ordinary temp>erature) is readily effected through the picrates the picrate of the liquid a-aceto compound is less soluble and the higher melting. 

The formation of alkylbenzenes, largely free from unaaturated compounds, provides another interesting application of organosodium compounds. Thus pure M-butylbenzene is readily obtained in good yield from benzyl sodium and n-propyl bromide. Benzyl-sodium is conveniently prepared by first forming phenyl-sodium by reaction between sodium and chlorobenzene in a toluene medium, followed by heating the toluene suspension of the phenyl-sodium at 105° for about 35 minutes ... 

Further evidence that the nitronium ion was not the electrophile in the uncatalysed reaction, and yet became effective in the catalysed reaction, came from differences in the orientation of substitution. The nitration of chlorobenzene in the uncatalysed reaction yielded only 43 % of the para compound, whereas, when the catalysed reaction was made important by adding some nitric acid, the ratio of substitution was that usually observed in nitration involving the nitronium ion ( 5.3.4). In the case of the uncatalysed reaction however, the reaction was complicated by the formation of nitrophenols. 

Chlorides are inert. However, the reaction ofp-chlorobenzophenone (9) with a styrene derivative proceeds satisfactorily at 150 C by u.sing dippb [l,4-bis(-diisopropylphosphino)butane] as a ligand to give the stilbene derivative 10. However, dippp [l,3-bis(diisopropylphosphino)propane] is an ineffective ligand[13]. On the other hand, the coupling of chlorobenzene with styrene proceeds in the presence of Zn under base-free conditions to afford the cis-stilbene 11 as a main product with evolution of H . As the ligand, dippp is... 

Chlorobenzene reacts with alkenes with bimetallic catalyses of Ni and Pd. Chlorobenzene is converted in situ into iodobenzene (14) by the Ni-cataiyzed reaction of Nal at 140 "C. NiBr2, rather than the Ni(0) complex, is found to be a good catalyst. Then the Pd-catalyzed reaction of the iodobenzene with acrylate takes place) 15]. 

Chlorination is carried out m a manner similar to brommation and provides a ready route to chlorobenzene and related aryl chlorides Fluormation and lodmation of benzene and other arenes are rarely performed Fluorine is so reactive that its reaction with ben zene is difficult to control lodmation is very slow and has an unfavorable equilibrium constant Syntheses of aryl fluorides and aryl iodides are normally carried out by way of functional group transformations of arylammes these reactions will be described m Chapter 22... 

Reaction of chlorobenzene with p chlorobenzyl chloride and aluminum chloride gave a mixture of two products in good yield (76%) What were these two products ... 

Noticeably absent from Table 23 3 are nucleophilic substitutions We have so far seen no nucleophilic substitution reactions of aryl halides m this text Chlorobenzene for example is essentially inert to aqueous sodium hydroxide at room temperature Reac tion temperatures over 300°C are required for nucleophilic substitution to proceed at a reasonable rate... 

A solution to the question of the mechanism of these reactions was provided by John D Roberts m 1953 on the basis of an imaginative experiment Roberts prepared a sample of chlorobenzene m which one of the carbons the one bearing the chlorine was the radioactive mass 14 isotope of carbon Reaction with potassium amide m liquid... 

Another ester synthesis employs the reaction of a long-chain ketone and pentaerythritol in xylene or chlorobenzene (14). Mixed esters have been produced using mixed isostearic and cyclohexane carboxyUc acids in trihromophosphoric acid, followed by reaction with lauric acid (15). 

The first detailed investigation of the reaction kinetics was reported in 1984 (68). The reaction of bis(pentachlorophenyl) oxalate [1173-75-7] (PCPO) and hydrogen peroxide cataly2ed by sodium saUcylate in chlorobenzene produced chemiluminescence from diphenylamine (DPA) as a simple time—intensity profile from which a chemiluminescence decay rate constant could be determined. These studies demonstrated a first-order dependence for both PCPO and hydrogen peroxide and a zero-order dependence on the fluorescer in accord with an earher study (9). Furthermore, the chemiluminescence quantum efficiencies Qc) are dependent on the ease of oxidation of the fluorescer, an unstable, short-hved intermediate (r = 0.5 /is) serves as the chemical activator, and such a short-hved species "is not consistent with attempts to identify a relatively stable dioxetane as the intermediate" (68). 

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