Chemical and thermochemical aspects of the ozonolysis of ethyl oleate: Decomposition enthalpy of ethyl oleate ozonide

Neat ethyl oleate was ozonized in a bubble reactor and the progress of the ozonolysis was followed by infrared (FT-IR) spectroscopy and by the differential scanning calorimetry (DSC). The ozonolysis was conducted till a molar ratio O-3/C=C approximate to 1 when the exothermal reaction spontaneously went to completion. A specific thermochemical calculation on ethyl oleate ozonation has been made to determine the theoretical heat of the ozonization reaction using the group increment approach. A linear relationship was found both in the integrated absorptivity of the ozonide infrared band at 1110 cm(-1) and the ozonolysis time as well as the thermal decomposition enthalpy of the ozonides and peroxides formed as a result of the ozonation. The DSC decomposition temperature of ozonated ethyl oleate occurs with an exothermal peak at about 150-155 degrees C with a decomposition enthalpy of 243.0 kj/mol at molar ratio 0(3)/C=C approximate to 1. It is shown that the decomposition enthalpy of ozonized ethyl oleate is a constant value (approximate to 243 klimol) at any stage of the 0(3) /C=C once an adequate normalization of the decomposition enthalpy for the amount of the adsorbed ozone is taken into consideration. The decomposition enthalpy of ozonized ethyl oleate was also calculated using a simplified thermochemical model, obtaining a result in reasonable agreement with the experimental value. (C) 2013 Elsevier Ireland Ltd. All rights reserved.