Study of complex properties of binary system of ethanol-methanol at   extreme concentrations
  At low concentrations of methanol in ethanol-methanol binary system, the molecular interactions are seen to be uniquely complex. It is observed that the ethanol aggregates are not strictly hydrogen-bonded complexes; dispersion forces also play a dominant role in the self- association of ethanol molecules. On the addition of small amount of methanol to ethanol, the dipolar association of ethanol is destroyed. The repulsive forces between the two moieties dominate the behavior of the binary system at lower concentration of methanol. At higher concentration of methanol (> 30%), the strength and extent (number) of formation of hydrogen bonds between ethanol and methanol increases. The geometry of molecular structure at high concentration favors the fitting of component molecules with each other. Intermolecular interactions in the ethanol-methanol binary system over the entire concentration range were investigated in detail using broadband dielectric spectroscopy, FTIR, surface tension and refractive index studies. Molecular Dynamics simulations show that the hydrogen bond density is a direct function of the number of methanol molecules present, as the ethanol aggregates are not strictly hydrogen-bond constructed which is in agreement with the experimental results. 
K Nilavarasi, Thejus R Kartha and V Madhurima
physics.chem-ph cond-mat.soft