Comparison of hydrogen bonding with gas-phase and broensted basicity of N(1),N(1)-dimethylformamidines. Substituent effects

Substituent effects observed for series of N(1),N(1)-dimethylformamidines in the hydrogen bonding reaction (as delta Delta G-HB with 4-fluorophenol) in non polar solvent (CCl4) have directly been compared with those found in the proton transfer reaction in the gas phase (as delta Delta GB) and polar solvent (as delta Delta G-alc in azeotropic ethanol). Significant differences between the aryl and alkyl subfamilies are observed. For aryl groups almost linear relations are found. There are only slight differences between the transmission of substituent field/inductive and resonance effects to the reaction centre in the hydrogen bonding and proton transfer reactions. For alkyl (simple alkyl, heteroalkyl and arylalkyl) groups no good relations are found. Hydrogen bonding basicity of alkyl groups depends on substituent steric, polarizability and field/inductive effects. Gas-phase basicity depends on substituent polarizability and field/inductive effects and Broensted basicity depends mainly on substituent field/inductive effect.