Thermochemical Properties of Diphenylalkanes

Abstract

The standard (p°) 0.1 MPa) molar enthalpies of vaporization ∆ 1 g H°m at the temperature T ) 298.15 K for diphenylmethane, (4-methylphenyl)phenylmethane, 1,1-diphenylethane, 1,1-bis(4-methylphenyl)ethane, 2-methyl-1,1-diphenylpropane, 1,1-diphenylpropane, and 1,1-diphenylbutane were obtained from the temperature dependence function of vapor pressure measured in a flow system. Standard molar enthalpies of formation ∆ f H°m(l) at the temperature T ) 298.15 K were measured using combustion calorimetry for 1,1-diphenylethane and 2-methyl-1,1-diphenylpropane. These experimental results together with the data available from the literature were used for the calculation of strain enthalpies of diphenylalkanes using the group-contribution procedure. The estimated strain enthalpies of the compounds studied were negligible within the boundaries of experimental uncertainties of about 1-2 kJ‚mol -1 . Thus no new strain corrections are needed for the prediction of the ∆ f H°m(g) of similarly shaped molecules by using groupadditivity procedures.

Relationships among strain energies of mono- and poly-cyclic cyclohexanoid molecules and strain of their component rings

“…The sample masses of amines were reduced to vacuum, taking into consideration the density value ρ (293) = 0.915 g · cm −3 for bis-piperidino-methane and The enthalpies of vaporization or sublimation of amines (see figure 1) were determined by using the method of transference in a saturated N 2 -stream. (7) To derive the standard molar enthalpy of vaporization…”

“…(1)(2)(3) At present, the group-additivity methodology (1,2) has successfully contributed to the further development of quantitative organic chemistry and correlation analysis. Our recent determinations of the gaseous enthalpies of formation f H o m (g) of ethers, (4) esters, (4) nitriles, (5) amines, (6) carboxylic acids, (7) and carboxylic acids derivatives (8) have contributed to the general development of the group-additivity procedure. However, prediction of f H o m (g) for the cyclic molecules is still thwarted due to numerous individual ring-corrections terms, which have to be measured experimentally.…”

Vapor pressures and enthalpies of vaporization of azides

“…When functional substituents are adjacent to geminal C-atom, their interactions unavoidable lied to stabilization or destabilization of a molecule [29][30][31]. Stabilization may occur due to electron delocalization from electron-releasing substituents (e.g.…”

“…The correlation of the enthalpies of vaporization with the number of C-atoms within the series of homologues is well documented. Vaporization enthalpies D g l H m ð298:15 KÞ appear to be a linear function of the number of carbon atoms of the alkanes [27][28][29][30][31][32][33] or nitriles [28]. The plot of D g l H m ð298:15 KÞ against the number of C-atoms in the alkyl chain of alkyl-azides (N C ) is presented in figure 3.…”

Thermochemistry of 2- and 4-biphenylmethanol

“…In the case of hole 1 t = 2.447 (8 independent measurements) and for hole 2 t = 2.365 (9 independent measurements) [36]. These results in conjunction with D f H m (C 6 H 6 , g) = (82.6 ± 0.7) kJ AE mol À1 [40], D f H m (C 12 H 10 , g) = (178.4 ± 2.6) kJ AE mol À1 [41][42][43][44], and D f H m (C 6 H 5 CH 2 OH, g) = À (99.2 ± 1.3) kJ AE mol À1 [40,[45][46][47][48] were used to assess DFT predictions for the enthalpy of reaction (10). This assessment also served as a test to the thermodynamic consistency of the experimental and theoretical data.…”