The SN mechanism in aromatic compounds. Part 41. Thermochemical calculations and experimental measurements of methanolysis of 1-fluoro-2,4-dinitrobenzene, picryl chloride, and picryl fluoride
Abstract
Rates and Armenius parameters for methanolysis of 1-fluoro-2,4-dinitrobenzene, picryl chloride, and picryl fluoride have been determined, and shown to be in satisfactory agreement with the results of a fundamental method of thermochemical calculation successfully applied previously to a wide range of SNAr reactions. These calculations also shed light on the sources of the large difference in nucleophilic strength of OMe– and MeOH, selected for the comparison of anionic and neutral forms of a nucleophile. The experimental results also lead to a comparison of the leaving group mobility of F and Cl in reactions with MeOH as nucleophile; as well as the activating power of an o-NO2 group, when there is an NO2 group in the other ortho-position. In the reaction of picryl chloride, the secondary reaction between product chloride ion and picryl methyl ether (demethylation) was avoided by carrying out the reaction in the presence of silver ion.