Studies on nitro-1,5-dimethylnaphthalenes and nitro-2,3-dimethylnaphthalenes
The synthesis of nitro-2,3-dimethylnaphthalenes has been undertaken, and fourteen previously unreported dinitro, trinitro, tetranitro and pentanitro derivatives of 2, 3-dimethylnaphthalene have been prepared. The synthesis of nitro-1, 5-dimethylnaphthalenes has also been undertaken, and seven previously unreported mononitro, dinitro, trinitro and tetranitro derivatives of 1, 5-dimethylnaphthalene have been prepared. The positive and negative ion mass spectra, electronic spectra and nuclear magnetic resonance spectra of these compounds have been recorded and discussed in terms of the structures of the compounds. The electron spin resonance spectra of the radical anions of two of the symmetrically substituted compounds have been recorded. The reactions of polynitro-2, 3-dimethyl-naphthalenes with methoxide ion and sulphite ion have been investigated, and the Meisenheimer complexes so formed characterised by NMR spectroscopy. In a number of cases solid Meisenheimer complexes have been isolated. The reaction of 4-nitro-1, 5-dimethylnaphthalene with hydroxide ion was found to produce dinitro derivatives of naphthastilbene and naphthabibenzyl, resulting from coupling via the 1-methyl group. The reactions of polynitro-1, 5-dimethylnaphthalenes with methoxide ion, sulphite ion, diethylamine and triethylamine in dimethylsulphoxide solvent have been investigated in situ by NMR spectroscopy, and benzyl-type ions resulting from abstraction of methyl hydrogen atoms were found to have been produced. The reaction of 2, 4, 6, 8-tetranitro-1, 5- dimethylnaphthalene with methoxide ion in tetrahydrofuran solvent was investigated, and a solid Meisenheimer complex was isolated. The association constants for the formation of charge-transfer complexes between benzene and the polynitro-1, 5-dimethlnaphthalenes and polynitro-2, 3- dimethylnaphthalenes have been determined by nuclear magnetic resonance spectroscopy, and it has been shown that polynitro-1, 5-dimethlnaphthalenes are stronger electron-acceptors than polynitro-2, 3-dimethylnaphthalenes. The rates of nitration of a number of mononitro, dinitro and trinitro derivatives of 1, 5-dimethylnaphthalene and 2, 3-dimethylnaphthalene have been investigated and the rates correlated with theoretical reactivity indices derived from Huckel Molecular Orbital calculations.