Abstract: The article presents a brief review of recent worldclass studies on vapor-liquid equilibrium (VLE) from the esters synthesis point of view, especially biodiesel production, by reactive distillation and a retrospective review of the key works of the Department of Chemical Thermodynamics and Kinetics (former Department of Theory of Solutions) of Institute of Chemistry of St. Petersburg University in the area of theoretical and experimental investigation of VLE in the systems with an esterification reaction. New experimental data on VLE in the system with reaction of ethyl acetate synthesis (acetic acid–ethanol–ethyl acetate–water) under isobaric conditions (atmospheric pressure) are reported. The activity coefficients, excess Gibbs energy and molar Gibbs energy of mixing of the components of reacting mixture were estimated. The chemical equilibrium constant was determined based on the experimental VLE data. The VLE data were correlated using the UNIFAC model, and it was found that the experimental and calculated data were in a sufficient agreement.