Tautomeric properties and gas-phase structure of 3-methyl-2,4-pentanedione

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• 作者：Natalya V. Belova ; Georgiy V. Girichev ; Heinz Oberhammer ; Nguen Hoang Trang ; Sergey A. Shlykov
• 关键词：¦Â-Diketones ; Tautomerism ; Electron diffraction ; Quantum chemical calculations ; Molecular structure
• 刊名：Journal of Molecular Structure
• 出版年：2012
• 出版时间：12 September, 2012
• 年：2012
• 卷：1023
• 期：Complete
• 页码：49-54
• 全文大小：449 K

文摘

The tautomeric and structural properties of 3-methyl-2,4-pentanedione, CH₃C(O)CH(CH₃)C(O)CH₃, have been studied by gas-phase electron diffraction (GED) and quantum chemical calculations (B3LYP and MP2 approximation with different basis sets up to aug-cc-pVTZ). Analysis of GED intensities resulted in the presence of 100(3) % enol tautomer at 274(7)K. Quantum chemical calculations predict enol concentrations from 8 % at MP2/6-31G(d,p) level to 100 % at B3LYP/aug-cc-pVTZ. This would show the failure of the MP2/6-31G(d,p) method. The enol ring possesses C_S symmetry with a strongly asymmetric hydrogen bond. The experimental geometric parameters are reproduced very closely by the B3LYP/aug-cc-pVTZ method.