Refractive indexes (rip), speed of sound (u) have been measured for binary mixtures of N-formylmorpholine + fluorobenzene, + chlorobenzene, + bromobenzene at 303.15, 308.15 and 313.15 K and at atmospheric pressure over whole composition range. Deviation in refractive index (Delta eta(D)), molar refraction (R-m) and deviation in molar refraction (Delta R-m) have been calculated using measured values of refractive indexes. Deviation in speed of sound (Delta u), deviation in isentropic compressibility (Delta k(s)) and deviation in acoustic impedance (Delta z) have been calculated from measured values of speed of sound. Theoretical refractive index values are calculated using nine relations namely Arago-Biot (A-B), Dale-Glastone (D-G), Lorentz-Lorentz (L-L), Weiner (WR), Heller (Hr), Newton (Nw), Eyring-John (E-J) Eykman (Eyk), Oster (Os) and their average deviation with experimental measured values have been calculated. Theoretical speed of sound is also calculated by using relations like Nomoto's relation, Ideal mixture relation, Junjie's relation, Free length theory relation and their average deviation from experimental values of speed of sound have been calculated. The FT-IR spectra's of pure components and their binaries at three different composition (v/v) 1:4,1:1 and 4:1 have been measured at 298.15 K for interpretation of intermolecular interaction between molecules of binary liquid mixtures. The results revealed negative values for deviation in molar refraction (Delta R-m), deviation in isentropic compressibility (Delta k(s)) and positive value for deviation in refractive index (Delta n(D)), deviation in speed of sound (Delta u) and deviation in acoustic impedance (Delta z). The results support the idea that strong interactions occur between molecules of binary mixtures. All the computed results were fitted with the Redlich-Kister type polynomial equation. (C) 2014 Elsevier B.V. All rights reserved.