3.2.1. Bimolecular dehydration of 1-butanol to DNBE
The theoretical r H0 1,(l) = −7.8 ± 9.8 kJ mol−1 estimated from the standard heats of formation presents a low absolute value suggesting that the exothermicity of the bimolecular dehy- dration of 1-butanol to di-n-butyl ether and water is very low, being almost an athermic reaction. This fact agree with the experimentally determined r H0 1,(l) = −0.3 ± 2.9 kJ mol−1 and is also in agreement with the constancy of Keq,1 with tem- perature (see Table 1). Furthermore, the experimental rH01,(l) found in this work is in the trend shown by values of other lin- ear symmetrical dialkyl ether found in the literature (Bringué et al., 2008, 2007; Casas et al., 2013) (Table 4). From the experi- mental rH01,(l) in Table 3 and fH0j,(l) of 1-butanol and water in Table 2 a value of f H0 DNBE,(l) = −370.5 ± 10.9 kJ mol−1 at 298.15K for DNBE can be obtained. This value agrees with that obtained by Colomina et al. (1965) from combustion enthalpies, enforcing the reliability of the experimental equi- librium data obtained for the main reaction.