Biphasic aldol condensation of n-butyraldehyde (nBAL), catalyzed by aqueous sodium hydroxide solution, is a part of the 2-ethyl hexanol synthesis process. In this study, the intrinsic reaction rate is obtained in the industrially relevant range 110-150 degrees C and 0.76-1.9 M NaOH, which is in the mass transfer regime dominated by the reaction in the film. A stirred cell is used to obtain stable interface between the organic and aqueous phases. The reaction dominated mass transfer regime was confirmed by the plateau region experiment and calculations of mass transfer. As a result, considering nBAL solubility and diffusivity, the rate was found to be 1st order in both nBAL and NaOH concentrations, along with 13.5 +/- 0.4 kcal/mol activation energy. The kinetic parameter sensitivity using different models for solubility, diffusivity and salt effect was also studied. This work demonstrates that, using penetration theory, it is possible to determine intrinsic reaction kinetics in the mass transfer regime, governed by reaction in the film. The results of the present work will be useful for the design and optimization of reactors for the commercial biphasic aldol condensation of nBAL. (C) 2013 Elsevier Ltd. All rights reserved.