Thermodynamic study of (alkyl esters +α,ω-alkyl dihalides) I: HmE and

Thermodynamic study of (alkyl esters+α,ω-alkyl dihalides) V. for 25 binary mixtures {xCu−1H2u−1CO2CH3+(1−x)α,ω-ClCH2(CH2)v−2CH2Cl}, where u=1 to 5, α=1 and v=ω=2 to 6

“…Hence, in figure 3a and b, respectively, showing equimolar values of H E m and V E m , it can be observed that, as the acid u chain of the methyl ester increases in length, the mixtures become less endothermic, see figure 3a. In contrast, for each ester the mixing enthalpy increases with the value of v. An explanation for the global behaviour would be similar to that given in previous studies [1,2] although some specific aspects can be mentioned. In figure 3a, the values of H E m are compared at intermediate concentration for the same a,x-dichloroalkanes, for the methyl and butyl esters [2].…”

“…Before use, the products were first degassified in an ultrasound bath and then kept for several hours on a 0.3 nm Fluka molecular sieve. The quality of the products was verified by measuring their refractive index n D and density q, at the temperature of 298.15 K. The values obtained for methyl esters and dichloroalkanes are not given in this work since they were slightly different than the values determined and presented previously [1,11].…”

“…In all cases, the k parameter are used as fixed amounts, depending on the property of the mixture to be correlated and calculated as described in detail below. Hence, to correlate the pairs ðx; V E m Þ this parameter is calculated as the quotient of molar volumes at the same working temperature [1,2,11]…”

“…In previous articles [1,2] values of H E m enthalpies and excess volumes V E m were presented for mixtures of ethyl and butyl esters with five a,x-dichloroalkanes, in an attempt to interpret the specific behaviour of these mixtures. From the results obtained, some conclusions were proposed revealing the existence of a set of different effects during the mixing process, even the presence of opposite effects in the dynamic of one specified mixture due to intra and/or intermolecular effects, appears to be evident.…”

“…As mentioned previously, the difficulty to interpret the behaviour of these mixtures has direct repercussions on the attainment of an adequate model to represent their mixing properties. Hence, for mixtures of ethyl esters [1] application of the UNIFAC model using the versions of Dang and Tassios [4] and Gmehling et al [5] produce totally unsatisfactory estimations. In a recent article [2], with mixtures of butyl esters, a global parameter was obtained for the ester/chloride interaction that gave place to substantially better predictions of enthalpies than by using the original parameters of Dang and Tassios [4].…”