Halogeno-2,4-dinitrobenzenes

However, this sequence may be altered as a result of changes in the nucleophilic agent and the solvent. Thus Hammond and Parks [23] noticed the rate of reaction of halogeno-2,4-dinitrobenzenes with aniline in ethanol to be the highest with fluorine and the lowest with chlorine F> Br> Cl. When N-methylaniline in nitrobenzene solution was used the sequence was Br>Cl>F - as mentioned above (Fierens and Halleux [24]). 

Temperature can also influence the rate of this nucleophilic displacement and alter the rate of reaction of different halogens. Brieux and Deulofeu [25] made the important observation that the temperature change may. affect the rate of reaction of various halogens differently. Thus the halogeno-2,4-dinitrobenzenes react with piperidine at the rates which can be arranged ... 

Interestingly, the nucleophilicity parameters were shown to apply fairly well for reactions with the four l-halogeno-2,4-dinitrobenzenes in water and in methanol. An exception was for reaction with the azide ion, which showed lower than expected reactivity in the substitution reaction [20]. Inclusion of an extra parameter increases the applicability of the equation so that Mayr [60] has shown that Equation 6.2, where S is a nucleophile specific slope parameter, allows the reactivities of very many nucleophiles... 

According to Beckwith, Miller and Leahy [22], the rates of the nucleophilic displacement of halogeno-2-dinitrobenzenes with sodium methoxide or sodium p- nitrophenate for the F, Cl, Br and I derivatives can be expressed by the figures 2880, 1, 0.690, 0.154 respectively. 

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