Vapor Pressure and Heat of Vaporization of Molecules That Associate in the Gas Phase

Abstract

A model of the temperature dependence of the vapour pressure and the heat of vaporization of associated liquids whose vapours contain associates is presented for two cases: dimers and linear associates in the gas phase. The results are analytic generalizations of the Clausius-Clapeyron equation, valid with accuracy of 0.1-1%, as demonstrated with 11 liquids: formic and acetic acids, methanol, ethanol, n-propanol, n-butanol, water, benzene, toluene, heptane, and isooctane. The model involves only readily available handbook parameters: the room-temperature vaporization heat, vapour pressure, heat capacities, 2 nd virial coefficient, and heat of dissociation of the dimers in the gas phase.

Sensing Magnetic Field and Intermolecular Interactions in Diamagnetic Solution Using Residual Dipolar Couplings of Zephycandidine

“…It is necessary to points out, that in Figure 5 c, the ced H /ced ratio for acetic acid- d 6 is smaller than that of metnanol- d 4 despite nearly identical Δ χ ax ( Table 1 ) and acetic acid being a stronger proton donor than methanol. This observation mirrors similar discrepancy observed for the ced determined experimentally from thermodynamic studies (see Figure 4 and discussion above) and suggest that experimental difficulties are related to presence of hydrogen-bonded dimers in the gas phase [ 40 , 41 , 42 , 46 ].…”

“…The reason for a relatively small ced/μ sol ratio in the case of acetic acid compared to other protic solvents (i.e., methanol and ethanol) could be explained by the underestimated experimental value of ced (427 Jcm −3 ), taken from reference [ 39 ]. The difficulties of evaluating reliable values of ced for carboxylic acids (acetic acid and formic acid in particular) from thermodynamic experiments are well documented and are related to the presence of both monomers and dimers in the gas phase [ 40 , 41 , 42 ]. This problem is illustrated in the Supplementary Material Table S3 which compares values of ced estimated for acetic acid in various sources [ 33 , 39 , 43 , 44 , 45 ].…”

Combined Experimental and Theoretical Studies on the Prediction of the Isobaric Vapor–Liquid Association Phenomena for Binary and Ternary Mixtures of Water, Ethanoic Acid, and Propanoic Acid

“…Wisniak and co-workers have developed a strategy for the correlation, prediction, and test of the two- and three-component systems containing the associating aliphatic acid components including homogeneous dimer and trimer and heterogeneous dimer. − In these works, although the association systems containing aliphatic acid monomer were considered to form homogeneous and heterogeneous dimer and trimer, and even polymer in vapor and liquid phases, all of the fundamental theoretical principles are based on a hypothesis without rigid calculation and simulation. In recent years, the study of aliphatic acid in association systems has aroused the interest of many researchers through molecular dynamics (MD) and quantum chemical (QC) simulation. − The association phenomena of ethanoic acid systems were investigated through combining MD and QC simulations by Ma’s group …”

An adsorption-precipitation model for the formation of injector external deposits in internal combustion engines

“…18 in Ref. [49]. A typical gasoline injector surface temperature (Ttip) is in the range 120-190 ○ C [50], therefore, during each cycle, the boiling temperature of the leaked droplet changes from well below the average surface temperature to well above it.…”

“…We present this derivation in order to analyse the limits of validity of Eq (49). There are two cases in which Eq (49) would fail.…”