Dimethylformamide (DMF) aqueous solution is a kind of simple biochemical model of biological molecular aqueous solutions. In this paper, ~1H NMR of DMF-H_2O system was measured at different temperatures to discuss molecular interactions in the mixtures. The association system was modeled on the equilibrium among H_2O, H_2O· DMF, (H_2O)_2 and (DMF)_2·H_2O and calculated by nonlinear least- square fitting. Association equilibrium constant K and the corresponding ΔH and ΔS were obtained by combined GA and levenberg- marquardt algorithm. In addition, DMF-CCl_4 and DMF-BuOH systems were also studied in order to further understand the nature of interactions in DMF-water mixture. Some peculiar phenomena were found and considered to be mainly caused by the special structure of liquid water, the hydrogen-bonding interactions and the conjugate system of amide.

Key words: DIMETHYLFORMAMIDE, WATER, 1HNMR, ASSOCIATION