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

Department of Chemistry, University of Porto, Oporto, Porto, Portugal
The Journal of Chemical Thermodynamics (Impact Factor: 2.3). 11/2005; 37(11):1168-1176. DOI: 10.1016/j.jct.2005.02.008

ABSTRACT The standard (p∘ = 0.1 MPa) molar enthalpy of formation for gaseous 2-phenylbenzimidazole (2-PhBIM) and 2-benzylbenzimidazole (2-BzBIM) were derived from the standard molar enthalpies of combustion, at T = 298.15 K, measured by static bomb calorimetry, and the standard molar enthalpy of sublimation, at T = 298.15 K, measured by Calvet microcalorimetry in the case of 2-phenylbenzimidazole or derived from the variation of the vapour pressures, determined by the Knudsen effusion technique, with temperatures between (393 and 412) K for 2-benzylbenzimidazole. Heat capacities, in the temperature ranges from (268.15 to 322.10) K for 2-phenylbenzimidazole and (270.15 to 316.02) K for 2-benzylbenzimidazole, were also measured with a differential scanning calorimeter. View Within Article

  • [Show abstract] [Hide abstract]
    ABSTRACT: Heat capacities (Cp,m) of solid anhydrous 1,10-phenanthroline (phen) and 2,9-dimethyl-1,10-phenanthroline (dmphen) were determined by differential scanning calorimetry using the three step method over the temperature range from 298K to about 5K (for phen) and 40K (for dmphen) below their melting temperatures. No further solid–solid phase transition occurs in the temperature range examined. In addition, the average melting temperature, molar enthalpy and molar entropy of fusion for phen and dmphen were also determined to be (391.1±0.1K, 11.8±0.1kJmol−1, and 30.0±0.3JK−1mol−1) and (435.9±0.3K, 17.6±0.3kJmol−1, and 40.3±0.6JK−1mol−1), respectively. The experimental heat capacity data were obtained and the respective second-order polynomial fitting equations were derived:Cp,m(phen,cr)/(J K−1 mol−1)=(−3905 ± 16)+(22.0 ± 1.0) (T/K)−(0.0289 ± 0.0015) (T/K)2 from 298.2 to 360.2 K, R2=0.9935; Cp,m(dmphen,cr)/(J K−1 mol−1)=(−2808 ± 14)+(17.1 ± 1.0) (T/K)−(0.0229 ± 0.0014) (T/K)2 from 298.2 to 393.2K, R2=0.9953.In particular the Cp,m values at T=298.15K for phen and dmphen were found to be (115±18 and 253±30)JK−1mol−1, respectively, where the associated uncertainties are twice the standard deviations of the mean.
    Thermochimica Acta 12/2007; 466(1):69-71. DOI:10.1016/j.tca.2007.10.001 · 2.11 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: We have investigated the energetic, structural, and other physical–chemical properties (aromaticity, intrinsic strain, hydrogen bond interaction) of 1,4-anthraquinone (1), its better known isomer 9,10-anthraquinone (2) and the derivatives 9-hydroxy-1,4-anthraquinone (3) and 9-methoxy-1,4-anthraquinone (4). In particular, the standard enthalpy of formation in the gas phase at 298.15 K of 1,4-anthraquinone was determined [ $\Updelta_{\text{f}}^{{}} H_{\text{m}}^{\text{o}} \left( {{\text{g}},{\mathbf{1}}} \right) \, = \, - 4 4. 9 { } \pm { 5}. 7\;{\text{kJ}}\;{\text{mol}}^{ - 1} ]$ Δ f H m o ( g , 1 ) = − 4 4.9 ± 5.7 kJ mol − 1 ] . Using isodesmic/homodesmotic reaction schemes, we have experimentally estimated: (i) the stabilization energy of 1 (162.2 ± 7.2 kJ mol−1) and 2 (193.2 ± 5.2 kJ mol−1), (ii) strength of intramolecular hydrogen bonding in 3 (HB = 79.8 ± 10.8 kJ mol−1), and (iii) additional strain energy due to peri-oxygen interaction in 4 (−34.2 ± 7.6 kJ mol−1). A computational study of these species, at the B3LYP/6-311++G(3df,2p) level, sheds light on structural, aromatic, intrinsic strain, or hydrogen bond effects and further confirmed the consistency of the experimental results.
    Structural Chemistry 12/2013; 24(6). DOI:10.1007/s11224-013-0295-0 · 1.90 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Molecular crystals of 2-phenylbenzimidazole, C13H10N2, exhibit a one-dimensional incommensurate structure. The Structure has been solved by charge flipping and refined using the superspace formalism in the (3 + 1) D superspace group C2/c(0b0) s0 with modulation wave-vector q = 0.368b*. The unit cell contains 8 molecules, each one disorderly occupying two configurations related by inversion center. The refinement based on a molecular model with two rigid-body parts per molecule includes up to second order Fourier amplitudes for the modulation. The displacive modulation involves a significant intra-molecular twist between the phenyl and the benzimidazole parts.
    Zeitschrift für Kristallographie 01/2006; 221(4):281-287. DOI:10.1524/zkri.2006.221.4.281 · 1.26 Impact Factor