Thermodynamic Analysis of Strain in the Five-Membered Oxygen and Nitrogen Heterocyclic Compounds

Abstract

Cyclopentane is conventionally strained. Replacement of a carbon atom by a heteroatom obviously impacts angular strain in the five-membered ring compounds. Changes of strains in the five-membered cycles are also caused by a double bond or atttached benzene rings. We studied the thermochemical properties of Indane, 2,3-dihydrobenzofuran, indoline, N-methyl-indoline, carbazole, and N-ethyl-carbazole to obtain a better quantitative understanding of the energetics associated with these compounds containing five-membered ring units. We used combustion calorimetry, transpiration method, and high-level first-principles calculations to derive gaseous enthalpies of formation of the five-membered heterocyclic compounds. Our new values together with the selected values for parent heterocyclic compounds, available from the literature, were used for calculation of the strain energies H(S) of five-membered C-, N-, and O-containing cycles. Quantitative analysis of the resulting stabilization or destabilization of a molecule due to interaction of benzene rings with the heteroatom has been performed.

Benchmark thermodynamic properties of 1,3-propanediol: Comprehensive experimental and theoretical study

“…However, the enthalpy of formation of 1,3-propanediol calculated from atomization procedure (equation (8)) was slightly lower than those from isodesmic reactions. Similar deviations have been observed for different series of compounds systematically [30,31,37]. In order to refine the atomisation results and provide an alternative approach to isodesmic reactions, a simple correction procedure has been suggested in our recent work [30].…”

“…The first one is around À465 kJ Á mol À1 from references [5,7], and the second group with the level of À480 kJ Á mol À1 from Knauth and Sabbah [6] and from the current work (see table 4). Our recent experiences with the high-level quantum-chemical calculations [30,31,[37][38][39] provide us a confidence to resolve the contradictions with 1,3-propanediol by using any suitable composite method, e.g. the G3MP2.…”

“…Since a significant discrepancy among available experimental enthalpies of formation for this compound has been found, any additional arguments to support the reliability of our new measurements are required. A valuable test of consistency of the experimental data could provide highlevel quantum-chemical calculations [30,31]. We have used the composite method G3MP2 for calculation of the gaseous enthalpy of formation of 1,3-propanediol for comparison with the experimental data.…”

A VUV Photoionization Study of the Combustion-Relevant Reaction of the Phenyl Radical (C6H5) with Propylene (C3H6) in a High Temperature Chemical Reactor

“…24 The aromatic, bicyclic indane molecule as well as its α-methylstyrene (2-phenylpropene) and 1-phenylpropene isomers are considered as important reaction intermediates and toxic byproducts in the combustion of fossil fuel ( Figure 1). 11,12,[25][26][27][28][29][30][31][32] The reaction of the phenyl radcial (C 6 H 5 ) with propylene (C 3 H 6 ) presents a potential synthetic routes to synthesize C 9 H 10 isomers and to access the C 9 H 11 potential energy surface.…”

Thermodynamic Evaluation of Potential Organic Hydrogen Carriers

“…[28] The data for the enthalpy of compound 17 (N-ethylcarbazole) were taken from Ref. [29]. The group contribution method suggested by Benson and Russ [30] was used for the hydrogenated forms of compounds 7 and 8 (decalin, tetradecahydroantracene) and the dehydrogenated form of compound 11 (4H-pyran), because no experimental data were available.…”