Chlorobenzenes, nitration

Store, of chlorobenzene Nitration of Hydrolysis to dinitrophenol, Trinitration ( Washing... 

The Table shows the variation with temperature of Rg, the moles of chlorobenzene nitrated per liter of the acid phase per second, and of k2 and [CB], each at a sulphuric acid strength close to 80. ... 

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. 

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. 

Characteristics of the system as nitrating reagents Wibaut, who introduced the competitive method for determining reactivities (his experiments with toluene, benzene and chlorobenzene were performed under heterogeneous conditions and were not successful), pointed out that solutions of nitric acid in acetic anhydride are useful in making comparisons of reactivities because aromatic compounds are soluble in them. ... 

The isomer proportions for the nitration of the chlorotoluenes, to be expected from the additivity principle, have been calculated from the partial rate factors for the nitration of toluene and chlorobenzene and compared with experimental results for nitration with nitric acid at o °C. The calculated values are indicated in brackets beside the experimental values on the following structural formulae. In general, it can be... 

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... 

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... 

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. 

Chemical Properties and Reactivity. LLDPE is a saturated branched hydrocarbon. The most reactive parts of LLDPE molecules are the tertiary CH bonds in branches and the double bonds at chain ends. Although LLDPE is nonreactive with both inorganic and organic acids, it can form sulfo-compounds in concentrated solutions of H2SO4 (>70%) at elevated temperatures and can also be nitrated with concentrated HNO. LLDPE is also stable in alkaline and salt solutions. At room temperature, LLDPE resins are not soluble in any known solvent (except for those fractions with the highest branching contents) at temperatures above 80—100°C, however, the resins can be dissolved in various aromatic, aUphatic, and halogenated hydrocarbons such as xylenes, tetralin, decalin, and chlorobenzenes. 

Nitration of benzene yields nitrobenzene, which is reduced to aniline, an important intermediate for dyes and pharmaceuticals. Benzene is chlorinated to produce chlorobenzene, which finds use in the preparation of pesticides, solvents, and dyes. 

Nitration of chlorobenzenes, mosdy monochlorobenzene in the United States, with nitric acid has wide industrial appHcations. 

Nitrochlorobenzene from chlorobenzene and nitric acid Nitration... 

Nitrodiphenyl ether has been prepared by heating p-nitro-chlorobenzene with potassium phenoxide and phenoD and by the nitration of diphenyl ether. ... 

Tnflic acid is an excellent catalyst for the nitration of aromatic compounds [.S7]. In a mixture with nitnc acid, it forms the highly electrophilic nitronium inflate, which can be isolated as a white crystalline solid Nitronium inflate is a powerful nitrating reagent in inert organie solvents and in tnflic acid or sulfuric acid. It nitrates benzene, toluene, chlorobenzene, nitrobenzene, m-xylene, and benzotn-fluoride quantitatively in the temperature range of-110 to 30 °C with exeeptionally high positional selectivity [87],... 

The nitration of nitrobenzene and of chlorobenzene are known to occur via the same mechanism the ring is initially attacked by NO2, yielding a cation intermediate for each isomer. When the nitration process is fully complete, the distribution of the various isomers of the final product varies greatly for the two compounds ... 

The darkest regions in the slices indicate the greatest electron density. The meta form of nitrated chlorobenzene and the para form of nitrated nitrobenzene retain the resonance structure to a much greater degree throughout the extent of the electron density. In contrast, the density in the less-favored conformations becomes more localized on the substituent as one moves outward from the plane of the carbon atoms. 

Figure 16.15 Carbocation intermediates in the nitration of chlorobenzene. The ortho and para intermediates are more stable than the meta intermediate because of electron donation of the halogen lone-pair electrons.

Mor alpha-) Dinitrophenol- Yel orthorhombic crysts from w, leaflets from ale mp 112—14° bp (decomp) d 1.683g/cc at 24°, 1.4829 at 72.5/4°. Sublimes when carefully heated volatile with steam. Can be prepd by the nitration of phenol, but this method is not considered commercially practicable because of partial decompn of the phenolic ring. A better method is by hydrolysis under pressure of 2,4-dinitrochloro-benzene, which in turn can be obtained by nitrating chlorobenzene. Other methods are given in Ref 1... 

Nitration of dinitrophenol. This is a multistage process. First chlorobenzene is nitrated to chlorodinitrobenzene as shown schematically below ... 

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