A systematic study on the intradiffusion and structure of N,N-dimethylformamide–water mixtures: by experiment and molecular dynamics simulation

Abstract

Intradiffusion coefficients of N,N-dimethylformamide (D_DMF) and water (D_W) in DMF–water mixtures were measured as a function of temperature, pressure and composition for the first time using the pulsed field gradient spin echo nuclear magnetic resonance technique. Then, molecular dynamics simulations for the abovementioned system at the same conditions were also conducted. The experimental D_DMF and D_W exhibited minimums at a DMF mole fraction (x_DMF) of 0.250–0.328, which indicates that two kinds of DMF–water complexes formed, namely DMF·3H₂O and DMF·2H₂O. The simulated D_DMF and D_W achieved a good agreement with the experimental values of this work, except at x_DMF = 0.250 or 0.328 that the overestimation is considerably large. We believe this phenomenon is due to the extremely strong DMF–water hydrogen bonding at such compositions, which is further supported by the followed calculation results of radial distribution functions, average number of hydrogen bonds and total potential energies. Finally, molecular dynamics trajectories of present simulation have successfully captured the hydrogen-bonded DMF–water complexes at the atomic level.