1 -Chloro-2,4-dinitrobenzene, nucleophilic

The hydroxy-nitro dye Naphthol Yellow S (6.233 Cl Acid Yellow 1) was discovered in 1879 by Caro and is still manufactured. It is produced by sulphonation of 1-naphthol to give l-naphthol-2,4,7-trisulphonic acid, followed by replacement of the 2- and 4-sulpho groups in nitric acid medium. Nucleophilic substitution of l-chloro-2,4-dinitrobenzene with 4-aminodiphenylamine-2-sulphonic acid gives Cl Acid Orange 3 (6.234). 

When the decomposition of the zwitterionic intermediate is rate-determining, the effect of the solvent is crucial since it may produce changes in the mechanisms and in the rate-determining step. A recent study of the kinetics of the reactions of 1-chloro-, 1-fluoro- and l-phenoxy-2,4-dinitrobenzene with piperidine, n-butylamine and benzylamine in ethyl acetate and THF indicated that these reactions resemble those in dipolar aprotic solvents when primary amines are the nucleophiles (i.e. that shown in equation 1, with... 

SjvAr reactions of nitroaromatics such as l-chloro-2,4-dinitrobenzene and 2,4,6-trinitroanisole with amines are accelerated in micelles or microemulsions49. As with anionic nucleophiles, the rate enhancement is mainly the effect of a high local concentration of both reactants18,31. 

There has been a useful review of phase-transfer catalysis in nucleophilic aromatic substimtion. A comparison has been reported of the reactions with nucleophiles of l-chloro-2,4-dinitrobenzene (substimtion) and 4-nitrophenyl diphenyl phosphate (dephosphorylation) in neutral micelles of dodecyl (10) and (23) polyoxyethylene glycol. In the substimtion reaction considerable amounts of ether may be formed by reaction with alkoxide ions at the micellar surface. Differences in reactivity of the two substrates are probably due to differences in their location in the micellar structures. ... 

Nucleophilic displacement of 2-chloro-3-phenylquinoxaline with methylamine at 100°-150° and with sodium phenoxide in excess of phenol of 100° gives the expected 2-methylamino- and 2-phenoxy-3-phenylquinoxalines.155 2-Chloroquinoxaline and its 3-phenyl derivative undergo ring closure with aminoacetaldehyde dimethylacetal to an imidazo[l,2-a]quinoxaline.136 Nucleophilic substitution of 2-chloro-quinoxaline with hydroxide ion in water is accelerated by cationic micelles and retarded by anionic micelles. These results were correlated with reactions of l-chloro-2,4-dinitrobenzene, and the characteristics of their transition states were discussed.137... 

SAMPLE SOLUTION (a) Sodium ethoxide is a source of the nucleophile CH3CH20" which displaces chloride from 1-chloro-2,4-dinitrobenzene. 

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... 

This method cannot be applied to polynitro amines, since these are so weakly basic that they can be diazotised only under special conditions in strongly acidic media (Section 6.7.1, p. 922). In such cases use may be made of the susceptibility to nucleophilic displacement of halogen when activated by ortho and para nitro groups. Thus the valuable reagent 2,4-dinitrophenylhydrazine (Expt 6.93) is readily prepared by reacting l-chloro-2,4-dinitrobenzene with hydrazine. Reaction with ammonia similarly gives 2,4-dinitroaniline (cognate preparation in Expt 6.93). 

Dinitration of p-chloro(trifluoromethyl)benzene will take place at the ring positions ortho to the chlorine. Compound A is 2-chloro-5-(trifluoromethyl)-l,3-dinitrobenzene. Trifluralin is formed by nucleophilic aromatic substitution of chlorine by dipropylamine. Trifluralin is N, A-dipropyl-4-(trifluoromethyl)-2,6-dinitroaniline. 

Plazek [28,28b] and Plazek and Talik [28a] stated recently that the reactivity of halogens in nitro derivatives of pyridine is much higher than in the similar benzene derivatives. Thus, at 20°C where only 0.5% of chloro-2,4-dinitrobenzene was subjected to nucleophilic displacement of chlorine by the amino group, the figure was 98.3% for 2-chloro-3,5-dinitropyridine. 

S. D. Ross [30] studied the nucleophilic displacement reaction in aromatic systems by examining the rate of reaction of chloro-2,4-dinitrobenzene with n-butyl-... 

The simplest example of an aromatic nucleophilic substitution is the SnAt reaction between l-chloro-2,4-dinitrobenzene and piperidine, the two-step mechanism of which, given in Eq. (5-26), is now fully established [501-503], It involves formation of a Meisenheimer-type zwitterionic intermediate via a dipolar activated complex, followed... 

However, nucleophilic substitution is helped by the presence of electron-withdrawing groups in the molecule. Consequently, l-chloro-4-nitrobenzene is hydrolysed to 4-nitrophenol at 200 °C and 4-nitroaniline can be produced using ammonia in ethanol at 150 °C. The presence of two nitro groups further activates the halogen and l-chloro-2,4-dinitrobenzene reacts easily with a variety of nucleophiles. 

Ionization constants of 2-carboxypiperazine and the three dicarboxylic acids have been determined (1684), and the nucleophilic reactivity of piperazine compared to other amines in reactions with l-chloro-2,4-dinitrobenzene has been measured (1685). The rate of quaternization of l-ethoxycarbonyl-4-methylpiperazine with allyl bromide (/ = 2.25 1/mol min) and methyl iodide (10A = 1.22) have been measured in acetone-water solution (1686). The composition and structure of the 2-methylpiperazine-carbon disulfide complex has been investigated it was a mixture of l-dithiocarboxy-3-methylpiperazine (138) and the 2-methylpiperazine salt of l,4-bis(dithiocarboxy)-2-methylpiperazine (1687). 

As in other nucleophilic substitutions, electron-withdrawing groups (NO2, CN, CO2H, SO3H) in ortho and para positions increase the reactivity of the aryl hahde to hydrolysis. For instance, chlorobenzene is best hydrolysed above 300 °C, whereas l-chloro-2,4-dinitrobenzene gives a 95% yield of 2,4-dinitrophenol at 100 °C . 

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