Thermochemical Properties (ΔfH°(298 K), S°(298 K), Cp(T)) and Bond Dissociation Energies for C1–C4 Normal Hydroperoxides and Peroxy Radicals

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• 作者：Heng Wang ; Joseph W. Bozzelli
• 刊名：Journal of Chemical & Engineering Data
• 出版年：2016
• 出版时间：May 12, 2016
• 年：2016
• 卷：61
• 期：5
• 页码：1836-1849
• 全文大小：441K
• 年卷期：0
• ISSN：1520-5134

文摘

Structure and thermochemical properties of the normal hydroperoxides, C_nH_2n+1OOH (1 ≤ n ≤ 4), and corresponding peroxy radicals, C_nH_2n+1OO·(1 ≤ n ≤ 4), are determined by density functional M06-2X, multilevel G4, composite CBS-QB3, and CBS-APNO level calculations. Unique to this study is that the Δ_fH°₂₉₈ values are determined using several isodesmic reactions which utilize experimental standard enthalpy data for CH₃OOCH₃ and CH₃CH₂OOCH₂CH₃ as reference species, where previous studies used atomization or work reactions with alcohols or other nonperoxide species. The S°₂₉₈ and C_p(T) (300 ≤ T/K ≤ 1500) from vibration, translation, and external rotation contributions are calculated based on the vibration frequencies and structures obtained from the density functional study. Potential barriers for the internal rotations are calculated at B3LYP/6-31+G(d,p) level, the hindered internal rotation contributions to S°₂₉₈ and C_p(T) are calculated using direct integration over energy levels of the internal rotational potentials. The results show the following Δ_fH°₂₉₈ values (units in kcal mol^–1): CH₃OOH (−31.0), CH₃CH₂OOH (−39.0), CH₃CH₂CH₂OOH (−44.0), CH₃CH₂CH₂CH₂OOH (−48.9),CH₃OO· (2.4), CH₃CH₂OO· (−6.2), CH₃CH₂CH₂OO· (−11.4), and CH₃CH₂CH₂CH₂OO· (−16.6). Bond dissociation energies for the R–OOH, RO–OH, ROO–H, R–OOj, and RO–Oj bonds are reported. The enthalpy values from the use of experimental data as a reference show very good agreement and support the data obtained from calculation methods. They should be used for reference values. Entropy and heat capacity values show good agreement with the calculation literature. The standard entropies for butyl hydroperoxide, propyl peroxy, and butyl peroxy are corrected.