Sorption Of Esters Research Articles

Retention Indices and Enthalpies of Sorption of Esters of Neopentyl Glycol on DB-1 Stationary Phase

The logarithmic retention indices and the enthalpies of sorption at the average temperature of an experiment and 298.2 K are determined via gas–liquid chromatography using DB-1 stationary phase for esters of neopentyl glycol and С2–С6 monobasic carboxylic acids of linear and branched structure at 423.2–523.2 K. The temperature dependences of the studied compounds’ retention indices are obtained, and the linearity of these dependences in the investigated range of temperatures is demonstrated. The values obtained for the enthalpies of sorption are analyzed.

Variation in the sorption energy of esters ofn-perfluoroalkanoic acids on chromatographic phases of different polarity

The contributions of methylene and difluoromethylene units of six homologous and six pseudohomologous series of esters ofn-perfluoroalkanoic acids to the differential molar free energy, enthalpy, and entropy of sorption on stationary phases of different polarities in glass capillary columns under isothermal conditions were calculated. The features observed characterize the peculiarities of the sorption of esters of polyfluorinated carboxylic acids on phases of different polarities and make it possible to estimate the enthalpy and entropy contributions to the energy of sorption of the esters, the effect of the temperature of the analysis and the length of the alkyl or polyfluoroalkyl chain on the retention parameters of the compound analyzed. The inversion of the retention order of trifluoroacetates and pentafluoropropionates in XE-60 nitrile-containing phase was found.

Polar and protective properties of esters

1. A number of esters used as aviation oils and hydraulic fluids have been investigated with respect to polar and electron donor-acceptor properties at an interface with metal. It has been shown that the majority of the esters are high in dielectric permeability and that they decrease the electron work function of metals, being electron donors and being sorbed at the > CO = group. 2. The least polar of the esters is the pentaerythritol ester of C5–C9 acids, which increases the electron work function. The sorption of esters on metal is in the nature of a physical adsorption. Satisfactory protective properties and the capability for rapid removal of an electrolyte from a metal surface are provided by the esters of mmethylcyclohexanol, adipic acid, and 2-ethylhexanol (No. 7), the monodecyl ester of diphenic acid (No. 8), and the didecyl ester of benzylsuccinic acid (No. 9). 3. Esters can be utilized as components of combination corrosion inhibitors, but all of the esters that were investigated are inferior in this respect to fatty acids.