The Kirkwood-Frohlich correlation factor (g), Eyring's parameters G and G* and the dipolar excess free energies of dilute solutions of formamide, acetamide, N-methyl acetamide, N,N-dimethyl formamide and N,N-dimethyl acetamide in 1,4-dioxan/benzene were obtained from a measurement of their static dielectric permittivities at 308 K. The fluid structure of these amides is discussed. Both in formamide and acetamide a dimeric linear chain with the individual dipoles more or less parallely oriented is preferred. In N-methyl acetamide, the antiparallel orientation of dipoles at lower concentrations turns into a parallel orientation with increase of concentration. In tertiary amides, with increase of concentration, parallel orientation of dipoles with global value of g tending to unity is observed. The dipolar excess free energy of mixing in a given solvent is of the order primary amide > secondary amide > tertiary amide. © Indian Academy of Sciences.