Of chlorobenzene

A mixture of the two mononitro-chlorobenzenes is prepared by nitration of chlorobenzene. Further nitration of the mixture or of either of the mononitro-compounds gives 2,4-dinitrochlorobenzene, m.p. 5 C, b.p. 315"C. 

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. 

Prepare a solution of benzencdiazonium chloride from 20 ml, (20 5 g.) of aniline precisely as in the preparation of chlorobenzene (p. 189), i.e, by dissolving the aniline in a mixture of 50 ml. of concentrated hydrochloric acid and 50 ml. of water, cooling to 5°, and then cautiously adding a solution of 17 g. of sodium nitrite in 40 ml. of water to the well-cooled and stirred aniline hydrochloride solution so that the temperature of the mixture remains between 5° and 10°. 

Ethylbenzene. Prepare a suspension of phenyl-sodium from 23 g. of sodium wire, 200 ml. of light petroleum (b.p. 40-60°) and 56 3 g. (50 9 ml.) of chlorobenzene as described above for p-Toluic acid. Add 43 -5 g. (30 ml.) of ethyl bromide during 30-45 minutes at 30° and stir the mixture for a further hour. Add water slowly to decompose the excess of sodium and work up the product as detailed for n-Butylbenzene. The yield of ethylbenzene, b.p. 135-136°, is 23 g. 

The name D.D.T. is derived from dichlorodiphenylfrichloroethane this is a misnomer since the name represents 27 different compounds. As commonly employed it refers to 2 2-6ts(p-chlorophenyl)-l 1 1-trichloroethane. It is conveniently prepared by the condensation of chlorobenzene and chloral hydrate in the presence of concentrated sulphuric acid ... 

In acetic acid the rates of nitration of chlorobenzene and bromo-benzene were fairly close to being first order in the concentration of aromatic, and nitration fully according to a first-order law was observed with O, m-, and/i-dichlorobenzene, ethyl benzoate and 1,2,4-trichloro-benzene. 

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. 

Using the partial rate factors for nitration of chlorobenzene, Ridd and de la Mare calculated the relative rates of nitration of the dichlorobenzenes, with respect to /)-dichlorobenzene, with the results shown below. Also given are results based on more recent nitrations in mixed... 

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... 

Usually, iodides and bromides are used for the carbonylation, and chlorides are inert. I lowever, oxidative addition of aryl chlorides can be facilitated by use of bidcntatc phosphine, which forms a six-membered chelate structure and increa.scs (he electron density of Pd. For example, benzoate is prepared by the carbonylation of chlorobenzene using bis(diisopropylphosphino)propane (dippp) (456) as a ligand at 150 [308]. The use of tricyclohexylphosphine for the carbonylation of neat aryl chlorides in aqueous KOH under biphasic conditions is also recommended[309,310]. 

Returning to Table 12 2 notice that halogen substituents direct an incoming electrophile to the ortho and para positions but deactivate the ring toward substitution Nitration of chlorobenzene is a typical example of electrophilic aromatic substitution m a halobenzene... 

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 ... 

Unlike the case of benzene in which ionization involves loss of a tt electron from the ring electron impact induced ionization of chlorobenzene involves loss of an elec tron from an unshared pair of chlorine The molecular ion then fragments by carbon-chlorine bond cleavage... 

The peak at m/z 77 m the mass spectrum of chlorobenzene m Figure 13 41 is attributed to this fragmentation Because there is no peak of significant intensity two atomic mass units higher we know that the cation responsible for the peak at m/z 77 cannot contain chlorine... 

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... 

Although nucleophilic aromatic substitution by the elimination-addition mecha nism IS most commonly seen with very strong amide bases it also occurs with bases such as hydroxide ion at high temperatures A labeling study revealed that hydroly SIS of chlorobenzene proceeds by way of a benzyne intermediate... 

Predict the products formed when each of the following isotopically substituted denvatives of chlorobenzene is treated with sodium amide in liquid ammonia Estimate as quantitatively as possible the composition of the product mixture The astensk ( ) in part (a) designates C and D in part (b) is... 

On the other hand labeling studies have shown that the base promoted hydro lysis of chlorobenzene (second entry m Table 24 3) proceeds by the elimination-addition mechanism and involves benzyne as an intermediate... 

Hydrolysis of chlorobenzene Heating chloroben zene with aqueous sodium hydroxide at high pres sure gives phenol after acidification... 

Examples of vibronic transitions involving non-totally symmetric vibrations are in the system of chlorobenzene, a C2 molecule. One 2 vibration V29, with a wavenumber of 615 cm in the X state and 523 cm in the A state, is active in 29q and 29j bands similar to the case shown in Figure 7.43. There are 10 2 vibrations in chlorobenzene but the others are much less strongly active. The reason is that (9J g/9029)eq is much greater than the corresponding terms for all the other 2 vibrations. 

The A B2 — system of chlorobenzene is electronically allowed, since B2 = which satisfies Equation (7.122). The Ojj band, and progressions in totally symmetric vibrations built on it, obtain their intensity in the usual way, through the first term on the right-hand side of Equation (7.131). 

Phenyllithium can be used as a solution in ethyl ether, but because of its limited stabUity (t 2 = 12 d at 35° C) it is commercially available in solution in mixtures, usuaUy 70 30 wt % cyclohexane ethyl ether (117). In this particular mixture of solvents, a 20 wt % solution, free of chlorobenzene, is stable for at least four months under an inert atmosphere (argon or nitrogen) in sealed containers at room temperature. Phenyllithium is also available in dibutyl ether solution (117). It is classified as a flammable Hquid. 

Dinitrochlorobenzene can be manufactured by either dinitration of chlorobenzene in filming sulfuric acid or nitration ofy -nitrochlorobenzene with mixed acids. Further substitution on the aromatic ring is difficult because of the deactivating effect of the chlorine atom, but the chlorine is very reactive and is displaced even more readily than in the mononitrochlorobenzenes. 

The first aromatic sulfone polymer produced commercially was introduced as Bakelite polysulfone but now is sold by Union Carbide under the trade name Udel. It is made by reaction of the disodium salt of bisphenol A (BPA) with 4,4 -dichIorodiphenyl sulfone in a mixed solvent of chlorobenzene and dimethyl sulfoxide (eq. 12). 

---