Enthalpy of Formation of Anisole: Implications for the Controversy on the O鈥揌 Bond Dissociation Enthalpy in Phenol

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• 作者：Ricardo G. Sim玫es ; Filipe Agapito ; Herm铆nio P. Diogo ; Manuel E. Minas da Piedade
• 刊名：Journal of Physical Chemistry A
• 出版年：2014
• 出版时间：November 20, 2014
• 年：2014
• 卷：118
• 期：46
• 页码：11026-11032
• 全文大小：248K
• ISSN：1520-5215

文摘

Significant discrepancies in the literature data for the enthalpy of formation of gaseous anisole, 螖_fH_mp class="stack">op>(PhOCH₃, g), have fueled an ongoing controversy regarding the most reliable enthalpy of formation of the phenoxy radical and of the gas phase O鈥揌 bond dissociation enthalpy, DHp>op>(PhO鈥揌), in phenol. In the present work 螖_fH_mp class="stack">op>(PhOCH₃, g) was reassessed using a combination of calorimetric determinations and high-level (W2-F12) ab initio calculations. Static-bomb combustion calorimetry led to the standard molar enthalpy of formation of liquid anisole at 298.15 K, 螖_fH_mp class="stack">op>(PhOCH₃, l) = 鈭?117.1 卤 1.4) kJ路molp>鈥?p>. The corresponding enthalpy of vaporization was obtained as, 螖_vapH_mp class="stack">op>(PhOCH₃) = 46.41 卤 0.26 kJ路molp>鈥?p>, by Calvet-drop microcalorimetry. These results give 螖_fH_mp class="stack">op>(PhOCH₃, g) = 鈭?70.7 卤 1.4) kJ路molp>鈥?p>, in excellent agreement with 螖_fH_mp class="stack">op>(PhOCH₃, g) = 鈭?70.8 卤 3.2) kJ路molp>鈥?p>, obtained from the W2-F12 calculations. The 螖_fH_mp class="stack">op>(PhOCH₃, g) here recommended leads to 螖_fH_mp class="stack">op>(PhOp>鈥?/sup>, g) = 55.5 卤 2.4 kJ路molp>鈥?p> and DH掳(PhO鈥揌) = 368.1 卤 2.6 kJ路molp>鈥?p>.