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

• We have ozonized ethyl oleate in a tubular bubble reactor.
• The main ozonation product is the ozonide of ethyl oleate.
• The thermal decomposition of the ozonide of ethyl oleate was studied using DSC.
• We have calculated the theoretical enthalpy of ethyl oleate ozonide decomposition.

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 O3/CC ≈ 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 °C with a decomposition enthalpy of 243.0 kJ/mol at molar ratio O3/CC ≈ 1. It is shown that the decomposition enthalpy of ozonized ethyl oleate is a constant value (≈243 kJ/mol) at any stage of the O3/CC 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.