Chlorobenzene, displacement

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 laboratory preparation of the Udel-type polymer has been described. Bis-phenol A is mixed with chlorobenzene (solvent) and dimethyl sulphoxide (active solvent) and heated to 60°C to obtain a clear solution. Air is displaced from the system by nitrogen or argon and an aqueous solution of caustic soda added. This results in a two-phase system, one predominantly chlorobenzene the... 

When potassium fluoride is combined with a variety of quaternary ammonium salts its reaction rate is accelerated and the overall yields of a vanety of halogen displacements are improved [57, p 112ff. Variables like catalyst type and moisture content of the alkali metal fluoride need to be optimized. In addition, the maximum yield is a function of two parallel reactions direct fluorination and catalyst decomposition due to its low thermal stability in the presence of fluoride ion [5,8, 59, 60] One example is trimethylsilyl fluoride, which can be prepared from the chloride by using either 18-crown-6 (Procedure 3, p 192) or Aliquot 336 in wet chlorobenzene, as illustrated in equation 35 [61],... 

The enamino ketone (49) was reported to give no identifiable products on reaction with N,N-dimethyl carbamoyl chloride 63). However, reaction of (49) with N,N-diethyl carbamoyl chloride in refluxing chlorobenzene gave the N-(3-diethyl-amino-5,5-dimethylcyclohex-2-en-1 -ylidene)pyrrolidinium salt, isolated as the perchlorate. The latter must have been formed as outlined in Scheme I, involving initial O carbamoylation followed by an addition-elimination reaction to give 138 cation which can react with diethylamino anion by a further addition-elimination displacement to give the product 46). 

The reaction of ethylene at -20°C and 1 atm with the phosphine-free catalyst prepared from 77-allylnickel chloride and ethylaluminum dichloride in chlorobenzene results in the rapid formation of a mixture of ethylene dimers with lesser amounts of higher oligomers. The dimer fraction consists mainly of 2-butenes and the trimer fraction of 3-methylpentenes and 2-ethyl-1-butene as well as a minor amount of hexene (97). From the composition of the products it can be concluded that the displacement reaction predominates over the insertion reaction when using the phosphine-free catalyst and that the direction of addition of both the H—Ni and C2H5—Ni species is mainly of the Ni — C2 type. 

There is certain similarity in the order of reactivities between SnAt displacement reactions and oxidative additions in palladium chemistry. Therefore, the ease with which the oxidative addition occurs for these heteroaryl chlorides has a comparable trend. Even a- and y-chloroheterocycles are sufficiently activated for Pd-catalyzed reactions, whereas chlorobenzene requires sterically hindered, electron-rich phosphine ligands. 

The difference between bromine and chlorine as the substituents is slight. I.R. measurements (Tamres, 1952) of the displacement of the OD-valency vibration of CH3OD dissolved in benzene derivatives also show only a slight difference between bromobenzene and chlorobenzene. 

A similar dependence of the first-order rate constants with respect to the quantity of added water has been reported for the reaction of sodium formate with 1,4-dichlorobutane and related displacement reactions, In these studies tetra- n-butylammonium hydrogen sulphate and tetra- n-butylammonium bromide were used as catalysts and chlorobenzene as the solvent. 

Miller and Walling1 6 have shown that both bromine and sulfonyl chloride groups can be displaced during the photochemical reaction of chlorine with p-bromobenzenesulfonyl chloride and that a similar displacement of the sulfonyl group of benzenesulfonyl chloride occurs to give chlorobenzene. 

Some nonionic organic compounds exhibit much stronger mineral surface affinities than we see for apolar and weakly monopolar compounds like chlorobenzenes and PAHs. In these cases, the organic sorbates are able to displace water from the mineral surface and participate in fairly strong sorbate sorbent intermolecular interactions. Example compounds include mtroaromatic compounds (NACs) such as the explosive, trinitrotoluene (TNT), or the herbicide, 2,4-dinitro-6-methyl-phenol, also called dinitro-o-cresol (DNOC). 

Although the simple aryl halides are inert to the usual nucleophilic reagents, considerable activation is produced by strongly electron-attracting substituents provided these are located in either the ortho or para positions, or both. For example, the displacement of chloride ion from l-chloro-2,4-dinitrobenzene by dimethylamine occurs readily in ethanol solution at room temperature. Under the same conditions chlorobenzene completely fails to react thus the activating influence of the two nitro groups amounts to a factor of at least... 

The reactivities of aryl halides, such as the halobenzenes, are exceedingly low toward nucleophilic reagents that normally effect displacements with alkyl halides and activated aryl halides. Substitutions do occur under forcing conditions of either high temperatures or very strong bases. For example, chlorobenzene reacts with sodium hydroxide solution at temperatures around 340° and this reaction was once an important commercial process for the production of benzenol (phenol) ... 

Exercise 14-20 In the hydrolysis of chlorobenzene-1-14C with AM aqueous sodium hydroxide at 340°, the products are 58% benzenol-1-14C and 42% benzenol-2-14C. Calculate the percentage of reaction proceeding (a) by an elimination-addition mechanism, and (b) by direct nucleophilic displacement. Would you expect the amount of direct displacement to increase, or decrease, if the reaction were carried out (a) at 240° and (b) with lower concentrations of sodium hydroxide Give your reasoning. 

Triarylphosphines were prepared by the reaction between lithium diphenylphosphide in THF and m-and p-iodotoluene (or the corresponding bromo compounds), 4-bromobiphenyl and p-dibromobenzene in yields of 70-80% (isolated after oxidation, as the phosphine oxides).143 The absence of cine substitution products is a synthetic advantage and would have been taken as a prima facie indication that the displacements are examples of the 5rn1 reaction, had the mechanism been recognized at the time. Operation of the radical ion mechanism in DMSO, or liquid ammonia, in which marginally improved yields are obtained, was confirmed by Swartz and Bunnett,48 but no extension to the scope of the reaction was made. Rossi and coworkers have developed a procedure for one-pot preparation of triarylphosphines starting from elemental phosphorus (Scheme 6).146 As an example of the synthesis of a symmetrical tri-arylphosphine, triphenylphosphine (isolated as its oxide) was obtained in 75% yield, with iodobenzene as the aryl halide (ArX in Scheme 6, steps i-iii only). Unsymmetrical phosphines result from the full sequence of reactions in Scheme 6, and p-anisyldiphenylphosphine (isolated as its oxide) was produced in 55% yield, based on the phosphorus used, when chlorobenzene (ArX) and p-methoxyanisole (AiOC) were used. 

Figure I Density modified displacement of chlorobenzene with 4 % Aerosol MA/OT + 25 % n-butanol (A) corresponds to initial injection of chlorobenzene, (B) and (C) correspond to increasing pore volumes of surfactant/alcohol flood ( (C) is a close-up of the outlet of the cell). Dyed chlorobenzene is outlined in figures above. Note that lines are also visible in B indicating the movement of dyed surfactant/alcohol solution.

Although chlorobenzene is rather inactive in usual reactions, its activity is enhanced by complex formation, and two products are formed by the reaction of stabilized carbanions on the complexed chlorobenzene 207, depending on the conditions [44], The anion of a-methy l propionitrile reacts at the meta position at —78 °C, and the mete-substituted product 208 is obtained by oxidation with I2. However, equilibration (rearrangement) of the carbanion occurs at 25 °C, because the attack of the carbanion is reversible, and the substitution product 209 of the chlorine is obtained. The fluorobenene 210, coordinated by Cr(CO)3, is very reactive. Reaction of y-butyrolactone to the o-lithiated fluorobenzene 211 gives rise to the alkoxide 212, which displaces the fluoride intramolecularly to give the cyclic ether 213 [52], In other words, the complex 211 can be regarded as the 1,2-dipolar synthon 214. However, Cr(CO)3-complexed aromatic bromide and iodide can not be used for the nucleophilic substitution. 

Hallworth and Carless (1 ) discuss several possibilities for the effect of light liquid paraffin on the stability of emulsions with light petroleum or chlorobenzene as the main components. They seem to prefer an explanation previously advanced by them and several other authors for the effect of fatty alcohol, namely that the increased stability is due to the formation of an interfacial complex between the additive and sodium hexadecyl sulphate. The condenced mixed film will resist coalescence primarily by virtue of its rheological properties. With mixed films of the present type, the importance of the film viscoelasticity lies in its ability to maintain electrical repulsion between approaching droplets by preventing lateral displacement of the adsorbed ions. The effective paraffinic oil has chains at least as long as those of the alkyl sulphate and will be associated by van der Waals forces with the hydrocarbon chain of the alkyl sulphate at the interface. 

Nucleophilic substitution of aryl halogen atoms requires significant energy input. Thus, in the Dow process for the synthesis of phenol from chlorobenzene, the chlorine atom is only successfully hydrolysed by aqueous sodium hydroxide at 300 °C under pressure. Displacement by ammonia is achieved at 200 °C over copper(I) oxide and conversion to benzonitrile occurs using copper(I) cyanide in boiling dimethylfor-mamide, HCONMe. ... 

The bimolecular displacement mechanism for nucleophilic aromatic substitution (shown here for chlorobenzene) is ... 

When an aryl halide like chlorobenzene is treated with the very strongly basic amide ion, NH2", in liquid ammonia, it is converted into aniline. This is not the simple displacement that, on the surface, it appears to be. Instead, the reaction involves two stages elimination and then addition. The intermediate is the molecule called benzyne (or dehydrobenzene). 

The additions of aryl halides to PdL2 complexes of Q-phos derivatives were recently reported by Barrios-Landeros and Hartwig179. The addition to Phi, PhBr and PhCl takes place through distinct mechanistic pathways (Scheme 5). Iodobenzene reacts by associative displacement of a phosphine, bromobenzene reacts by rate-limiting dissociation of phosphine, and chlorobenzene reacts by reversible dissociation of phosphine, followed by oxidative addition. 

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