Heats of vaporization of esters by the gas chromatography–calorimetry method

Abstract

A recently developed gc–calorimetry procedure involving a combination of gas chromatography and heat of solution measurements has been used to measure heats of vaporization of 17 esters, including methyl 2,2-dimethylpropanoate, butyl acetate, glyceryl triacetate, diethyl phthalate, methyl 9-octadecenoate, and 12 methyl esters of C3- to C15-fatty acids. Comparison with measurements of ΔHv reported in the literature indicates that the gc–calorimetry method often has smaller uncertainties in measurements (0.25 to 1.00 kJ mol−1) and more consistent methylene increments for the series of fatty acid methyl esters. Two of the experimental ΔHv measurements which differ appreciably from recent literature values have been verified by vaporization calorimetry.

Transpiration method: Vapor pressures and enthalpies of vaporization of some low-boiling esters

“…In the similar way vapor pressures were measured by the static method [18]. However, the molar enthalpy of vaporization of methyl butanoate g l H m (298.15 K) = 43.7 ± 0.3 kJ mol −1 measured in this work (see Table 2) agrees well within error bars with the most of available indirect results presented in Table 2, and is also in a close agreement with the direct calorimetric results reported in the literatures [12][13][14].…”

“…3. The results measured using the ebulliometry [22] and using static diaphragm manometry [18] are very consistent with each other and with our new results from the transpiration method (see Table 1) and appropriate enthalpies of vaporization derived from these three techniques are in a close agreement (see Table 2) and also with the direct calorimetric results [13,14,20].…”

“…4. The enthalpies of vaporization derived from the ebulliometry spread from 46 to 49 kJ mol −1 (see Table 2) but their average is in a good agreement with the calorimetric measurements [13,20] and data obtained using static diaphragm manometry [18]. Our new enthalpy of vaporization value for methyl hexanoate from the transpiration method is also consistent with those from other techniques.…”

“…of vaporization from their results. That is why the original published experimental results [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27] were treated using Eqs.…”

A correlation for heat of vaporization of pure compounds

“…Vetere [28] ΔH v /RT c =A+BT r +CT r D 24 Somayajulu I [29] ΔH v =A(1/T r − 1)+B(1− T r ) 3/8 +C(1− T r ) 18 [24], [54], [55], [56], [57], [58], [ [24], [41], [54], [57], [58], [59], [70], [71], [ [24], [38], [41], [54], [57], [72], [103], [104], [ [46], [49], [58], [70], [117], [118], [119], [120], [121], [122], [123], [ [38], [49], [58], [72], [74], [109], [110], [127], [132], [133], …”