Journal of Chemical Software
Online ISSN : 1883-8359
Print ISSN : 0918-0761
ISSN-L : 0918-0761
Evaluation of Enthalpies of Benzene—Monosubstituted Benzene interactions by Semi-Empirical MO Calculations. Their Relationship to the Experimental Enthalpies Determined by GLPC
Tadashi ENDOTakahiro IIDANobuhide FURUYAYumiko YAMADAMasato M. ITO
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1999 Volume 5 Issue 2 Pages 81-92

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Abstract

Enthalpies of benzene—monosubstituted benzene interactions were evaluated by semi-empirical MO calculations of heats of formation for (i) the benzene (PhH) dimer and (ii) benzene—monosubstituted benzene (PhX) pairs. Calculation methods, initial intermolecular distances (rI), and so on were investigated for the benzene dimer. The interaction enthalpy and optimized geometry calculated with PM3 were consistent with the previous experimental and theoretical results. As initial arrangements of PhH—PhX systems, one parallel (P) and four vertical arrangements (Vr , Vp , Vm , and Vb) were chosen (Figure 1). In the case of Vp or Vm arrangement where the lowest H atom at the para or meta position to substituent X in PhX was located above the centroid of PhH, calculated enthalpies of the interactions (ΔΔHf) between PhH and PhX had close correlation with experimental ones (ΔΔHt) determined by gas-liquid partition chromatography (GLPC), with the correlation coefficient (ρ) as large as 0.94 (Figure 5); differences between the experimental ΔΔHt values and the ΔΔHt values calculated from the correlation equation were less than ca. 0.1 kcal mol-1 . With the other arrangements except for Vp, no appreciable relationship was observed between the ΔΔHf and ΔΔHt (Figures 2, 3, and 4).

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© 1999 by the Chemical Software Society of Japan
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