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. 2015 Mar 6;16(3):5271-84.
doi: 10.3390/ijms16035271.

Mechanistic studies on the dibenzofuran formation from phenanthrene, fluorene and 9-fluorenone

Shanqing Li  1 , Qingzhu Zhang  2
Affiliations

Mechanistic studies on the dibenzofuran formation from phenanthrene, fluorene and 9-fluorenone

Shanqing Li et al. Int J Mol Sci. .

Abstract

We carried out molecular orbital theory calculations for the homogeneous gas-phase formation of dibenzofuran from phenanthrene, fluorene, 9-methylfluorene and 9-fluorenone. Dibenzofuran will be formed if ∙OH adds to C8a, and the order of reactivity follows as 9-fluorenone > 9-methylfluorene > fluorene > phenanthrene. The oxidations initiated by ClO∙ are more favorable processes, considering that the standard reaction Gibbs energies are at least 21.63 kcal/mol lower than those of the equivalent reactions initiated by ∙OH. The adding of ∙OH and then O2 to phenanthrene is a more favorable route than adding ∙OH to C8a of phenanthrene, when considering the greater reaction extent. The reaction channel from fluorene and O2 to 9-fluorenone and H2O seems very important, not only because it contains only three elementary reactions, but because the standard reaction Gibbs energies are lower than -80.07 kcal/mol.

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Figures

Scheme 1
Scheme 1
Illustrative structural diagrams for phenanthrene, fluorene, 9-methylfluorene, 9‑fluorenone, dibenzofuran and a generic modeling for them.
Figure 1
Figure 1
Dibenzofuran formation paths from phenanthrene (Phe); (A) Reaction scheme, enthalpies were calculated at 1000 K, and energy unit is kcal/mol; (B) Standard Gibbs energy changes for the overall reactions; (C) Activation Gibbs energies for the overall reactions (We accumulate the Gibbs energy change of each elementary reaction in turn, and the maximum value in a reaction route at given temperature is selected for the ∆G‡).
Figure 2
Figure 2
Dibenzofuran and 9-fluorenone formation paths from fluorene (Flu); (A) Reaction scheme, enthalpies were calculated at 1000 K, and energy unit is kcal/mol; (B) Standard Gibbs energy changes for the overall reactions; (C) Activation Gibbs energies for the overall reactions.
Figure 3
Figure 3
Dibenzofuran formation paths from 9-fluorenone (9FO); (A) Reaction scheme, enthalpies were calculated at 1000 K, and energy unit is kcal/mol; (B) Standard Gibbs energy changes for the overall reactions; (C) Activation Gibbs energies for the overall reactions.
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