Mechanism of the Kolbe-Schmitt reaction with lithium and sodium phenoxides

Russian Journal of Physical Chemistry (Impact Factor: 0.56). 08/2007; 81(9):1392-1397. DOI: 10.1134/S0036024407090087

ABSTRACT The mechanisms of the carboxylation reactions of lithium and sodium phenoxides are investigated by means of the DFT method
with a CEP-31 + G(d) basis set. The introduction of diffusion functions does not affect the outcome of the calculations. As a consequence, the
results of this investigation are in good agreement with the findings obtained by means of the LANL2DZ basis set. Lithium
phenoxide yields only salicylic acid in the Kolbe-Schmitt reaction. The reaction of sodium phenoxide can proceed in the ortho and para positions, but the para-substituted product can be expected at a very low concentration in the reaction mixture. The deviation of lithium and sodium
phenoxides from the mechanisms of carboxylations of other alkali metals is a consequence of the small ionic radii of lithium
and sodium.

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Available from: Zoran Marković, May 17, 2014
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    ABSTRACT: This work is an extension of our investigations of the Kolbe--Schmitt reaction mechanism. The last step in the para route of the carboxylation reaction of alkali metal phenoxides is investigated at the B3LYP/LANL2DZ level of theory. Among several examined pathways, two mechanisms are proposed: the one involving a successive rearrangement of hydrogen and the other one based on the formation of free radicals. The former pathway is energetically comparable to the last step of the carboxylation reaction in the ortho position, whereas the latter pathway requires higher activation energy. Bearing in mind that the Kolbe--Schmitt reaction is performed at high temperatures, we assume that both reaction paths are plausible.
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