Molecular structure, barriers to internal rotation, and the enthalpy of formation of cumene hydroperoxide PhCMe2OOH: a DFT study |
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Authors: | A N Egorova M V Vener I S Zhukov G D Kozak V G Tsirelson |
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Institution: | (1) D. I. Mendeleev University of Chemical Technology of Russia, 9 Miusskaya pl., 125047 Moscow, Russian Federation |
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Abstract: | Conformational analysis of cumene hydroperoxide PhCMe2OOH (1) has been carried out using the density functional methods B3LYP/6-31G(d,p) and B3LYP/6-311+G(3df,2p). Ignoring rotation
of methyl groups, molecule 1 has seven conformers differing in orientation of the — CMe2OOH fragment relative to the benzene ring and in mutual position of atoms in this fragment. The molecular structures, relative
energies, and statistical distribution of the conformers were determined, and intramolecular rotational barriers were estimated.
The enthalpies of formation of all conformers of molecule 1 were calculated using two approximations with inclusion of zero-point vibrational energy and temperature correction. Calculations
using the isodesmic reaction (IDR) scheme made it possible to reduce the systematic error of the determination of the enthalpy
of reactions. The total enthalpy of formation of compound 1 calculated with inclusion of statistical distribution of rotamers equals −19.7±3.6 kcal mol−1. The combination of the B3LYP/6-31G(d,p) approximation and the IDR scheme gives fairly accurate results (relative error is
±0.4 kcal mol−1) as compared to those obtained with the extended basis set 6-311+G(3df,2p).
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1157–1164, June, 2008. |
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Keywords: | molecular structure rotational barrier enthalpy of formation cumene hydroperoxide quantum chemical calculations density functional method |
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