Experimental and computational thermochemical studies of benzoxazole and two chlorobenzoxadole derivatives

Cimas, Álvaro; Silva, Manuel A.V. Ribeiro da

doi:10.1016/j.jct.2012.08.028

Cited by 21 publications

(6 citation statements)

References 39 publications

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“…The optimized geometries of the two benzoxazoles, very similar to those we have observed previously for nonsubstituted benzoxazole [ 11 ] and methylbenzoxazoles, [ 12 ] are presented in Figure 3. The geometry optimization was performed at the B3LYP/6‐31G(d) level of theory.…”

Section: Resultssupporting

confidence: 71%

“…In this work, the energy associated with the substituent interactions in the benzoxazole core were studied by calculating the respective increments for substitution of H atoms for NH 2 , NO 2 , or CH 3 groups (Figure 4) and comparing them with the corresponding substitutions in benzothiazole. For these calculations,

∆_{f} H_{m}^{°} ()(, g)

values at T = 298.15 K were used: benzoxazole, (32.7 ± 2.3); [ 11 ] 2‐methylbenzoxazole, (−27.2 ± 2.3); [ 12 ] benzothiazole, (199.5 ± 2.6); [ 39 ] 2‐methylbenzothiazole, (140.5 ± 2.8); [ 39 ] 2‐aminobenzothiazole, (179.8 ± 1.9); [ 40 ] and 2‐methyl‐6‐nitrobenzothiazole, (124.0 ± 3.0) kJ·mol −1 . This latter value was calculated (Table S8) using the same high‐level molecular orbital calculations (G3(MP2)//B3LYP method).…”

Section: Resultsmentioning

confidence: 99%

“…Thus, this study represents a contribution for the determination of thermochemical and thermophysical properties, following previous studies in diheteroatom‐containing aromatic benzoxazoles. [ 8–12 ] Hence, we describe a new experimental and computational energetic study on two benzoxazoles, ABO and 2‐methyl‐6‐nitrobenzoxazole (MNBO), whose structures are shown in Figure 1.…”

Section: Introductionmentioning

confidence: 99%

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Effects of the functional groups amino and nitro on the reactivity of benzoxazoles and comparison with homologous benzothiazoles

Silva

2020

J of Physical Organic Chem

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The energetic study of 2‐aminobenzoxazole (ABO) and 2‐methyl‐6‐nitrobenzoxazole (MNBO) has been developed using experimental and computational tools. The enthalpies of combustion, of fusion, and of sublimation of these compounds were measured by static‐bomb combustion calorimetry, differential scanning calorimetry, and Calvet microcalorimetry drop‐technique and/or the Knudsen‐effusion method. Additionally, we calculated the gas‐phase standard molar enthalpies of formation of these compounds, as well as of 2‐methyl‐6‐nitrobenzothiazole (MNBT), through high level ab initio calculations, at the G3(MP2)//B3LYP level of theory. Furthermore, the energetic effects associated with the presence of the amino and nitro groups on the core of benzoxazole or benzothiazole molecules were also evaluated, as well as stabilizing electronic interactions occurring in the molecules. The latter were investigated through Natural Bonding Orbital (NBO) of the corresponding wave functions. Finally, the thermodynamic stability of the titled compounds was evaluated and a comparison with their sulfur heteroanalogs was achieved. In the gaseous phase, the oxygen derivatives exhibit the lowest tendency to decompose into their constituent elements at standard conditions.

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Section: Resultssupporting

confidence: 71%

∆_{f} H_{m}^{°} ()(, g)

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effects of the functional groups amino and nitro on the reactivity of benzoxazoles and comparison with homologous benzothiazoles

Silva

2020

J of Physical Organic Chem

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“…Experimental and computational studies for compounds with pentagonal ring cores, with two nitrogen atoms or a nitrogen and an oxygen or sulfur as heteroatoms, in the positions 1,3-, has been studied recently [5][6][7][8]. Other studies on the energetic of five-membered nitrogen heterocycles fused to a benzenic ring [9][10][11] have been also described in the recent literature. For hydantoin, there are studies [12] reporting the determination of the corresponding enthalpies of combustion and formation in the crystalline phase, although the results do not match with those obtained for related compounds and those presented in this work.…”

Section: Introductionmentioning

confidence: 99%

Experimental and computational study of the energetics of hydantoin and 2-thiohydantoin

Silva¹,

Cimas²,

Vale³

et al. 2013

The Journal of Chemical Thermodynamics

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The standard (p°= 0.1 MPa) molar energies of combustion of hydantoin and 2-thiohydantoin were measured by static and rotating bomb combustion calorimetry, respectively. The standard molar enthalpies of sublimation, at T = 298.15 K, were derived from the temperature dependence of the vapour pressures of these compounds, measured by the Knudsen-effusion technique, and from high temperature Calvet microcalorimetry. The conjugation of these experimental results enables the calculation of the standard molar enthalpies of formation in the gaseous state, at T = 298.15 K, which are discussed in terms of structural contributions.We have also estimated the gas-phase enthalpy of formation from high-level ab initio molecular orbital calculations at the G3MP2B3 level of theory, being the computed values in good agreement with the experimental ones. Furthermore, this composite approach was also used to obtain information about the gas-phase basicities, proton and electron affinities and adiabatic ionization enthalpies.

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“…A considerable number of experimental combustion and formation data have been published for heterocyclic compounds, including hetarenes, unsubstituted and substituted by functional groups just mentioned. According to the hetero elements in the ring system, they have been subdivided into N x -heterocycles (where x is 1 to 4) , N,O-heterocycles [424][425][426][427][428][429][430][431][432][433], N,S-heterocycles [434][435][436][437][438], O x -heterocycles [439][440][441][442][443][444][445][446][447][448][449][450][451][452], and S x -heterocycles [280,[282][283][284][453][454][455][456][457][458][459][460][461]. A small number of papers contributed data for hetarenes with several element combinations [462][463][464]…”

Section: Sources Of Heat-of-combustion and Formation Datamentioning

confidence: 99%

Revision and Extension of a Generally Applicable Group-Additivity Method for the Calculation of the Standard Heat of Combustion and Formation of Organic Molecules

Naef

Acree

2021

Molecules

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The calculation of the heats of combustion DH°c and formation DH°f of organic molecules at standard conditions is presented using a commonly applicable computer algorithm based on the group-additivity method. This work is a continuation and extension of an earlier publication. The method rests on the complete breakdown of the molecules into their constituting atoms, these being further characterized by their immediate neighbor atoms. The group contributions are calculated by means of a fast Gauss–Seidel fitting calculus using the experimental data of 5030 molecules from literature. The applicability of this method has been tested by a subsequent ten-fold cross-validation procedure, which confirmed the extraordinary accuracy of the prediction of DH°c with a correlation coefficient R2 and a cross-validated correlation coefficient Q2 of 1, a standard deviation σ of 18.12 kJ/mol, a cross-validated standard deviation S of 19.16 kJ/mol, and a mean absolute deviation of 0.4%. The heat of formation DH°f has been calculated from DH°c using the standard enthalpies of combustion for the elements, yielding a correlation coefficient R2 for DH°f of 0.9979 and a corresponding standard deviation σ of 18.14 kJ/mol.

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Experimental and computational thermochemical studies of benzoxazole and two chlorobenzoxadole derivatives

Cited by 21 publications

References 39 publications

Effects of the functional groups amino and nitro on the reactivity of benzoxazoles and comparison with homologous benzothiazoles

Effects of the functional groups amino and nitro on the reactivity of benzoxazoles and comparison with homologous benzothiazoles

Experimental and computational study of the energetics of hydantoin and 2-thiohydantoin

Revision and Extension of a Generally Applicable Group-Additivity Method for the Calculation of the Standard Heat of Combustion and Formation of Organic Molecules

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