Substituent effects on enthalpies of formation of nitrogen heterocycles: 2-substituted benzimidazoles and related compounds.
The enthalpies of combustion, heat capacities, enthalpies of sublimation and enthalpies of formation of 2-tert-butylbenzimidazole (2tBuBIM) and 2-phenylimidazole (2PhIM) are reported and the results compared with those of benzene derivatives and a series of azoles (imidazoles, pyrazoles, benzimidazoles and indazoles). 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++G(d,p) on B3LYP/6-31G optimized geometries. The comparison of experimental and calculated values of all studied compounds bearing H (unsubstituted), methyl (Me) ethyl (Et), propyl (Pr), isopropyl (iPr), tert-butyl (tBu), benzyl (Bn) and phenyl (Ph) groups show remarkable homogeneity. The remarkable consistency of both the calculated and experimental results allows us to predict with reasonable certainty the missing experimental values. The crystal and molecular structure of the 2-benzylbenzimidazole (2BnBIM) has been determined by X-ray analysis. The observed molecular conformation permits the crystal being built up through N-H...N hydrogen bonds and van der Waals contacts between the molecules. An attempt has been made to relate the crystal structure to the enthalpies of sublimation.
Departamento de Cristalografía, Instituto de Química-Física Rocasolano, C.S.I.C., Serrano 119, E-28006 Madrid, Spain.
Lourdes
L
Infantes
Otilia
O
Mó
Manuel
M
Yáñez
María Victoria
MV
Roux
Pilar
P
Jiménez
Juan Z
JZ
Dávalos
Manuel
M
Temprado
Manuel A V
MA
Ribeiro da Silva
Maria das Dores M C
Md
Ribeiro da Silva
Luísa M P F
LM
Amaral
Pilar
P
Cabildo
Rosa
R
Claramunt
José
J
Elguero
D000465:Algorithms; D001393:Azoles / Q000737:chemistry; D001555:Benzene Derivatives / Q000737:chemistry; D001562:Benzimidazoles / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D007093:Imidazoles / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D009584:Nitrogen / Q000737:chemistry*; D013816:Thermodynamics
C521465:2-tert-butylbenzimidazole; D001393:Azoles; D001555:Benzene Derivatives; D001562:Benzimidazoles; D007093:Imidazoles; C059194:2-phenylimidazole; D009584:Nitrogen