Substituent and ring effects on enthalpies of formation: 2-methyl- and 2-ethylbenzimidazoles versus benzene- and imidazole-derivatives

Abstract

The enthalpies of combustion, heat capacities, enthalpies of sublimation and enthalpies of formation of 2-methylbenzimidazole (2MeBIM ) and 2-ethylbenzimidazole (2EtBIM ) are reported and the results compared with those of benzimidazole itself (BIM ). Theoretical estimates of the enthalpies of formation were obtained through the use of atom equivalent schemes. The necessary energies were obtained in single-point calculations at the B3LYP/ 6-311 þ G(d,p) on B3LYP/6-31G* optimized geometries. The comparison of experimental and calculated values of benzenes, imidazoles and benzimidazoles bearing H (unsubstituted), methyl and ethyl groups shows remarkable homogeneity. The energetic group contribution transferability is not followed, but either using it or adding an empirical interaction term, it is possible to generate an enormous collection of reasonably accurate data for different substituted heterocycles (pyrazole-derivatives, pyridine-derivatives, etc.) from the large amount of Á f H o m ð gÞ values available for substituted benzenes and those of the parent (pyrazole, pyridine) heterocycles.

Thermochemical properties of two benzimidazole derivatives: 2-Phenyl- and 2-benzylbenzimidazole

“…The aim of the extension of this research is not only to compare the effect of the substituents in the heterocycle of the bicyclic molecules with the corresponding monocyclic heteromolecules, but also to enlarge the knowledge on the energetics of benzimidazoles, some of which are known to have antiviral activity [11][12][13][14][15][16] used in fungicides [17], in therapy of intoxications [18], as protective agents for metal surfaces of printed-circuit boards [18], as inhibitors on steel corrosion [19], in sunscreen cosmetics [20], etc. The work already published concerning these benzazole molecules, involves the energetic properties of 2-R-benzimidazoles, R = methyl [10], ethyl [10], propyl [9] and isopropyl [9]. The present work reports the experimental results of thermochemical properties for two other 2-R-benzimidazole derivatives, with aromatic substituents R = phenyl or benzyl, whose structural formula are represented in figure 1.…”

“…Our research groups have been involved in a systematic experimental and theoretical study about the substituent and ring effects on the energetics of diazole derivatives, derived from imidazole and pyrazole [1][2][3][4][5][6][7][8] and, recently, we extended our research work on bicyclic molecules derived from imidazoles fused to the aromatic ring C [9,10]. The aim of the extension of this research is not only to compare the effect of the substituents in the heterocycle of the bicyclic molecules with the corresponding monocyclic heteromolecules, but also to enlarge the knowledge on the energetics of benzimidazoles, some of which are known to have antiviral activity [11][12][13][14][15][16] used in fungicides [17], in therapy of intoxications [18], as protective agents for metal surfaces of printed-circuit boards [18], as inhibitors on steel corrosion [19], in sunscreen cosmetics [20], etc.…”

Interplay of thermochemistry and Structural Chemistry, the journal (volume 19, 2008) and the discipline

“…Spectroscopic characterization and X-ray single-crystal structure analyses of synthesized compounds were performed. While the enthalpies of formation of benzimidazole and some alkyl derivatives have been measured and compared with corresponding benzene derivatives [124], no such data and resulting interrelations are available for any vinyl or otherwise substituted species with unsaturated substituents such as the above pyridinylvinyl compounds.…”

Thermochemical study of some chloro and bromo alkyl substituted phthalimides: Structural–energetic correlations

“…The wide range of properties and applications of these types of compounds led to the enormous amount of research that has been carried out on the last decades and that still keeps the interest of many world laboratories. The systematic experimental and theoretical study on the energetics of nitrogen aromatic heterocycles has been, for some years, one of the main interests of our research group, as being partially presented in two review papers [1,2] and lately extended to other aromatic nitrogen heterocycles like azols [3][4][5][6][7][8][9], phenylpyridine isomers [10], chloropyridines [11], pyrimidines [12], quinoxalines [13] and quinolines [14,15]. More recently our research interested have focused on non-aromatic nitrogen heterocycles with the piperidine ring [16][17][18][19][20][21][22] and with the phthalimide structure [23,24].…”