Nucleophilic attacks on LL (Low LUMO) substrates. Part 3. Molecular stacking of 9-methylenefluorene derivatives as a source of zero-order reactions

Shmaryahu Hoz, Zeev Gross, Oov Speizman

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3 Scopus citations

Abstract

The reactions of the three activated dibenzfulvene derivatives 9-dicyanomethylene-, 9-dinitromethylene-, and 9-nitromethylene-fluorene (FDCN, FDN, and FN respectively) with NaOH in water containing 1% dioxane were followed at 25°C. The reactions were found to be zero-order in the substrate and zero-order within a run in the hydroxide. Overall, the reaction was first-order in the hydroxide. Under these conditions zero-order kinetics are also obtained for the reaction of CN- with FDCN. 'Normal' first-order kinetics were obtained under these conditions for the reaction of OH- with 1,1-diphenyl-2,2-dinitroethylene as well as for FDN when the dioxane concentration was increased to 25% (v/v). It is suggested that owing to their planar structure these substrates undergo efficient stacking in the solution with only a small fraction left as a free reactive monomer at the saturation concentration. A relatively rapid equilibrium between the monomer and the aggregate maintains a constant monomer concentration in the solution. A Tyndall effect of the aggregated particles could not be observed with the naked eye. The particles also pass through a Whatman No. 1 filter paper. However, other observations such as solvent and temperature effects on the absorbance in the u.v. range strongly support the suggested explanation.

Original languageEnglish
Pages (from-to)1143-1146
Number of pages4
JournalJournal of the Chemical Society, Perkin Transactions 2
Issue number8
DOIs
StatePublished - 1985

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