Determination of the enthalpy of evaporation of pentaerythritol esters of various structures using gas chromatographic retention characteristics

Objectives. The work set out to prepare and chromatographically analyze pentaerythritol esters, use gas chromatography to determine the Kováts logarithmic retention indices and enthalpies of sorption, and evaluate the enthalpy of evaporation of pentaerythritol tetraesters based on linear correlations with enthalpies of sorption and logarithmic retention indices. Methods. The synthesis was carried out in an isothermal stirred reactor at T = 393.2 K at a molar ratio of pentaerythritol to carboxy lic acid of 1 : 4 in self-catalysis mode to avoid side reactions that occur during aggressive acid catalysis. The obtained samples were analyzed using Chromatec Analytic hardware and software complex based on a Kristall-2000M chromatograph equipped with a capillary column (60 m × 0.32 mm × 0.5 μm) having BP-1 grafted stationary phase (100 % dimethylpolysiloxane). The analysis conditions were as follows: isothermal mode; column temperature, 433.2–603.2 K; evaporator and detector temperatures, 623.2 K; gas flow split, 1 : 50; carrier gas, helium; volume of injected sample, 0.15 µL; diluent of reaction samples, methanol. Results. For the first time, the values of the Kováts retention indices and enthalpies of sorption were found for 31 pentaerythritol esters of various structures (mono-, di-, tri-, and tetramethanoates; 2-methylpentanoates; 4-methylpentanoates; 2,2-dimethylbutanoates; 2-ethylbutanoates; octanoates; nanoates; and decanoates). The obtained correlation equations were used to estimate the enthalpy of evaporation of pentaerythritol tetraesters (for 7 compounds, data were obtained for the first time). Conclusions. The retention parameters were found as linear dependencies with a high degree of correlation (R 2 > 0.99) in the studied temperature range (433.2–603.2 K). The enthalpies of evaporation calculated based on the enthalpies of sorption and logarithmic retention indices within the limits of error of the correlation dependencies coincide with the literature data and the values predicted by the quantitative structure–property relationship method. The obtained data can be used to design units for separating multicomponent mixtures and identify these compounds.