Benchmark Thermodynamic Properties of Methyl- and Methoxybenzamides: Comprehensive Experimental and Theoretical Study

Abstract

The enthalpies of formation of 2-, 3-, and 4-CH3-benzamide, as well as for 2-CH3O-benzamide were measured by using combustion calorimetry. Vapor pressures of the isomeric CH3- and CH3O-benzamides were measured by using the transpiration method. The enthalpies of sublimation/vaporization of these compounds at 298 K were obtained from temperature dependencies of vapor pressures. The enthalpies of solution of the isomeric CH3- and CH3O-benzamides were measured with solution calorimetry. The enthalpies of sublimation of m- and p-substituted benzamides were independently derived with help of a solution calorimetry based procedure. The enthalpies of fusion of the CH3-benzamides were derived from DSC measurements. Thermochemical data on CH3- and CH3O-benzamides were collected, evaluated, and tested for internal consistency. A simple incremental procedure has been suggested for a quick appraisal of vaporization enthalpies of substituted benzamides. The high-level G4 quantum-chemical method was used for mutual validation of the experimental and theoretical gas phase enthalpies of formation. A remarkable ability of the G4 based atomization procedure to calculate reliable enthalpies of formation has been established for the set of aliphatic and aromatic amides. An outlook for the proper validation of the G4-AT procedure was discussed.

Thermochemistry of Substituted Benzamides and Substituted Benzoic Acids: Like Tree, Like Fruit?

“…This work complements our previous studies of the thermodynamic properties of amides and benzoic acid derivatives . We have performed experimental and computational studies of the substituted benzamides presented in Figure .…”

“…It is well established that values of the intramolecular interactions of substituents in the 1,3‐ and 1,4‐positions on the benzene ring are very close in size. A very good linear correlation between the 3‐R‐benzamides and 3‐R‐benzoic acids was observed when they were correlated separately.…”

Calculation of Five Thermodynamic Molecular Descriptors by Means of a General Computer Algorithm Based on the Group-Additivity Method: Standard Enthalpies of Vaporization, Sublimation and Solvation, and Entropy of Fusion of Ordinary Organic Molecules and Total Phase-Change Entropy of Liquid Crystals

“…Experimental data of vaporization enthalpies have essentially been extracted for this work from the large collection of Acree, Jr. and Chickos [ 8 ] and Chickos et al [ 10 , 11 , 12 , 13 , 14 ], supplemented by recent data from a number of further authors publishing experimental vaporization values of several acetophenones [ 23 ], aliphatic tertiary amines [ 24 ], azidomethyl- N -nitrooxazolidines [ 25 ], benzamides [ 26 ], benzocaine [ 27 ], bisabolol and menthol [ 28 ], crown ethers [ 29 ], N , N -dialkyl monoamides [ 30 ], fenpropidin and phencyclidine [ 31 ], flavors [ 32 ], long-chain fluorinated alcohols [ 33 ], whiskey- and metha-lactone [ 34 ], halogenated fluorenes [ 35 ], ibuprofen and naproxen [ 36 ], imidazo[1,2- a ]pyrazine and phthalazine [ 37 ], insect pheromones [ 38 ], morpholines [ 39 ], organo(thio)phosphates [ 40 ], dialkyl phthalates [ 41 ], nitrogen heteroaromatics [ 42 ], phenylimidazoles [ 43 ], 2-acetylthiophene [ 44 ], dicarboxylic n -pentyl esters [ 45 ], and cyclic amines, ethers and alcohols [ 46 ]. The result of the atom-group parameters, based on 3581 compounds, is summarized in Table 1 .…”

Calculation of Five Thermodynamic Molecular Descriptors by Means of a General Computer Algorithm Based on the Group-Additivity Method: Standard Enthalpies of Vaporization, Sublimation and Solvation, and Entropy of Fusion of ordinary Organic Molecules and Total Phase-Change Entropy of Liquid Crystals

“…Experimental data of vaporization enthalpies have essentially been extracted for this work from the large collection of W. E. Acree Jr. and J. S. Chickos [8] and J. S. Chickos et al [10][11][12][13][14], supplemented by recent data from a number of further authors publishing experimental vaporization values of several acetophenones [23], aliphatic tertiary amines [24], azidomethyl-N-nitro-oxazolidines [25], benzamides [26], benzocaine [27], bisabolol and menthol [28], crown ethers [29], N,N-dialkyl monoamides [30], fenpropidin and phencyclidine [31], flavors [32], long-chain fluorinated alcohols [33], whiskey-and methalactone [34], halogenated fluorenes [35], ibuprofen and naproxen [36], imidazo[1,2-a]pyrazine and phthalazine [37], insect pheromones [38], morpholines [39], organo(thio)phosphates [40], dialkyl phthalates [41], nitrogen heteroaromatics [42], phenylimidazoles [43], 2-acetylthiophene [44], dicarboxylic n-pentyl esters [45], and cyclic amines, ethers and alcohols [46]. The result of the atom-group parameters, resting on 3581 compounds, is summarized in Table 1.…”

“…This precondition has been thoroughly followed when selecting experimental data from literature. Again, as in the previous chapter, the main contribution of experimental sublimation values has been provided by the compendium of W. E. Acree Jr. et al [8], supplemented by a number of later publications, referencing the heat of sublimation of acetophenones [23], substituted benzamides [26], crown ethers [29], long-chain fluorinated alcohols [33], halogenated fluorenes [35], tricyclic nitrogen heteroaromatics [42], polyphenylbenzenes [47], adamantylideneadamantane [48], cyclic N,N'-thioureas [49], indole-3-carboxylic acids [50], vanillyl alcohol [51], alkanoylphenols [52], adamantanes [53], six-membered ring aliphatics [54], fluoroquinolones [55], oxazolidinones [56], nitrogen-containing substituted adamantanes [57], 2,7-di-t-butylfluorene [58] and nitroimidazoles [58]. (row B and F at the bottom of Table 2) exhibit a higher scatter of the experimental data in comparison with the heat-of-vaporization data.…”