This paper studies liquid-liquid equilibrium (LLE) of the type 2 systems (water+valeric acid+dibasic ester or monobasic ester or alcohol) at T=(298.2 +/- 0.1) K and p=(101.3 +/- 0.7) kPa. Equilibrium distribution of valeric acid onto (water+solvent) two-phase system is better for more structured diethyl sebacate and ethyl caprylate as compared to less structured diethyl succinate, diethyl malonate, ethyl valerate, and isoamyl alcohol. The two-phase envelope size and the tie line slope on the phase diagrams are varying as follows: ethyl caprylate>diethyl sebacate>ethyl valerate>diethyl succinate approximate to diethyl malonate>isoamyl alcohol. The SERLAS-integrated (solvation energy relation for liquid associated systems-integrated) molecular model with nine physical descriptors, originated from LSER (linear solvation energy relation) principles in conjunction with group-contribution method, is proposed and applied to the prediction of type 2 LLE properties. By combining SERLAS with UNIFAC-Dortmund, we are able to get along with a simultaneous impact of both methods for satisfactorily simulating type 2 phase behaviour so long as solvent effects are concerned. SERLAS, SERLAS-modified, SERLAS-integrated, and UNIFAC-original models have been stringently tested for consistency in reproducing phase equilibrium properties with average deviations inferior to 28.8%, 44.3%, 21.3%, and 30.4%, respectively.