Experimental standard molar enthalpies of formation of some 4-alkoxybenzoic acids

The present work is part of a research program on the energetics of the linear 4-n-alkoxybenzoic acids, aiming the study of the enthalpic effect of the introduction of an alkoxy chain in the position 4- of the benzoic acid ring. In this work, we present the results of the thermochemical research on 4-n-alkoxybenzoic acids with the alkoxy chain length n = 2, 4, and 8.The standard ($p^{°}=0.1\text{MPa}$) molar enthalpy of formation of crystalline 4-ethoxybenzoic acid, 4-butoxybenzoic acid, and 4-(octyloxy)benzoic acid was measured, at T = 298.15 K, by static-bomb calorimetry. These values, combined with the values of standard molar enthalpies of sublimation, were used to derive the standard molar enthalpies of formation in the gaseous phase.

4-Alkoxybenzoic acid	$-{\mathrm{\Delta }}_{\text{c}}{U}_{\text{m}}^{°}(\text{cr})/(\text{kJ}·{\text{mol}}^{-1})$	$-{\mathrm{\Delta }}_{\text{f}}{H}_{\text{m}}^{°}\text{(cr})/(\text{kJ}·{\text{mol}}^{-1})$	$-{\mathrm{\Delta }}_{\text{f}}{H}_{\text{m}}^{°}(\text{g})/(\text{kJ}·{\text{mol}}^{-1})$
4-Ethoxybenzoic acid	4362.7 ± 1.3	605.5 ± 1.8	482.2 ± 2.0
4-Butoxybenzoic acid	5677.3 ± 2.0	647.1 ± 2.5	518.1 ± 2.6
4-(Octyloxy)benzoic acid	8269.0 ± 3.3	767.9 ± 3.9	604.9 ± 4.1
Keywords:
本文献已被 ScienceDirect 等数据库收录！