Dielectric investigation of hydrogen-bonding in hydroxynitrotoluenes and nitroresorcinols

The dipole moments of hydroxynitrotoluenes and nitroresorcinols have been measured in dioxan and benzene (and carbon tetrachloride with two of the nitroresorcinols). The values of µ/D (±ca. 0.05), with dioxan first, are: 3-hydroxy-2-nitrotoluene (I) 4.0, 3.2; 4-hydroxy-2-nitrotoluene (II) 4.0, 3.8; 5-hydroxy-2-nitrotoluene (III) 5.25, 4.9; 6-hydroxy-2-nitrotoluene (IV) 5.25, 4.75; 4-hydroxy-3-nitrotoluene (V) 3.3, 3.45; 2-nitroresorcinol 2.9, 2.25 and 2.45 (CCl4); 2,4-dinitroresorcinol 4.9, 3.4 and 4.05 (CCl4); 4,6-dinitroresorcinol 2.7 (dioxan). The solvent effects with (II), (III) and (IV) are attributed to intermolecular hydrogen bonding with dioxan, and this conclusion is supported by the measured infra-red OH stretching frequencies for these compounds, which decrease in passing from benzene to dioxan. The results for (V) are consistent with specific attachment of the dioxan molecule to the intramolecular hydrogen bonded system. It is suggested that (II), (IV) and (V) exist mainly in the cis-configuration in benzene solution. The solvent effects with 2-nitroresorcinol and 2,4-dinitroresorcinol are attributed largely to fission of the intramolecular hydrogen bonds and formation of intermolecular hydrogen bonds with the solvent molecules.