Thermodynamic Properties of N-Methyl-Substituted Ethane-1,2-diamines: Experimental and Computational Study

Abstract

Vapor pressures for four N-methyl-substituted ethane-1,2-diamines were measured using the transpiration method. Enthalpies of vaporization were derived from the temperature dependence of the vapor pressures. Consistency of the experimental data was assessed and confirmed with group-additivity (GA) and quantum-chemical (QC) methods. Further confirmation of the results is provided through combined assessment with properties reported in the literature for the parent compound ethane-1,2diamine and a group of alkyl-substituted alkane-1,2-diamines. The effective application of modern QC methods in critical evaluation of enthalpies of vaporization and enthalpies of formation is demonstrated.

Critical Evaluation of Thermodynamic Properties for Halobenzoic Acids Through Consistency Analyses for Results from Experiment and Computational Chemistry

“…Refs. [12][13][14]. The demonstration of consistency between the computations and experiment provides a mutual validation of the two methods, together with an increase in confidence in the overall critical evaluation.…”

“…Uncertainties estimated by Cox and Pilcher 82 are given first and the original uncertainties given by Smith et al 97 e.g., the predictive method of Chickos et al 163 for liquid heat capacity and correlations of the enthalpy of vaporization by Verevkin and co-workers. 12 The correlation of properties involving solids is typically of limited application and has large uncertainties because the property values are strongly dependent on the nature of the crystal packing and intermolecular associations in the solid state. For example, the group-additivity method of Domalski and Hearing 164 for heat capacities at T 5 298.15 K is valid for hydrocarbons only, while the more widely applicable 163 has a reported uncertainty of ;50 J K 21 mol 21 (twice the standard error), which for benzoic acid is 35% of the heat capacity of the crystal at T 5 298.15 K. 33 For these reasons, we have chosen not to attempt the correlation of enthalpies of sublimation for halobenzoic acids, but instead we derive enthalpies of vaporization with the purpose of demonstrating trends for compound families.…”

“…15 and 16). The quality of such computations has improved such that uncertainties for some modern computations on selected systems are comparable to the best experimental results, and these can be used as a check on experimentally derived values of D f H o m (g), 12 and this approach is used in the present work with application to the twelve monohalogenated (F, Cl, Br, and I) benzoic acids. Direct computation of thermodynamic properties in condensed states is an active area of research today, but has not reached the threshold of uncertainty necessary for use in the critical evaluation of experimental results.…”

Comment on “Studies on Thermodynamic Properties of FOX-7 and Its Five Closed-Loop Derivatives”

“… a The Gaussian 09 implementation W1Usc (UCCSD­(T) instead of ROCCSD­(T) along with a small spin contamination correction) of the W1 method was employed for open-shell atoms. b The most reliable experimental values summarized in refs − . c Reference , calculated using the atomization energy approach. …”

Energetics of LOHC: Structure-Property Relationships from Network of Thermochemical Experiments and in Silico Methods

“…However, in order to get the liquid phase ∆ f H o m (liq, 298 K)-values according to Equation (4), vaporization enthalpies of hydrogenated pyrazine derivatives are required. In a series of our recent papers [48][49][50][51][52] we have developed group-additivity parameters for prediction of ∆ g l H o m (298 K)-values of aliphatic nitrogen-containing compounds. Compilation of the group contributions required for estimation of vaporization enthalpies of different cyclic amines is given in Table S6.…”