Tautomeric Properties and Gas-Phase Structure of 3-Chloro-2,4-pentanedione

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• 作者：Natalya V. Belova ; Heinz Oberhammer ; Georgiy V. Girichev ; Sergey A. Shlykov
• 刊名：Journal of Physical Chemistry A
• 出版年：2008
• 出版时间：April 10, 2008
• 年：2008
• 卷：112
• 期：14
• 页码：3209 - 3214
• 全文大小：253K
• 年卷期：v.112,no.14(April 10, 2008)
• ISSN：1520-5215

文摘

The tautomeric properties of DER=0>-chlorinated acetylacetone, 3-chloro-2,4-pentanedione CH₃C(O)-CHCl-C(O)CH₃, have been investigated by gas electron diffraction (GED) and quantum chemical calculations (B3LYPand MP2 approximations with different basis sets up to cc-pVTZ). Analysis of the GED intensities resultedin the presence of 100(2)% enol tautomer at 269(8) K. The following skeletal geometric parameters (r_h1values) of the molecule, which possesses C_s symmetry, were derived: r(C=C) = 1.378(3) Å, r(C-C) =1.450(3) Å, r(C=O) = 1.243(3) Å, r(C-O) = 1.319(3) Å, r(O-H) = 1.001(4) Å, r(C-Cl) = 1.752(4) Å,C-C=C = 121.3(1.0)deg.gif">, C=C-O = 119.9(1.2)deg.gif">, C-C=O = 119.1(1.2)deg.gif">. Due to very small contributionsof the keto tautomer in -chlorinated acetylacetone and its parent species, the effect of -chlorination ontautomeric properties cannot be derived from experimental data. Quantum chemical calculations (B3LYP/6-31G**, B3LYP/cc-pVTZ, and MP2/cc-pVTZ) predict that -chlorination of acetylacetone has no pronouncedeffect on the tautomeric properties. On the other hand, similar calculations for 1-chloro-1,3-butanedion, ClC(O)-CH₂-C(O)CH₃, demonstrate that chlorination in one ddle"> position destabilizes the enol tautomer. In bothchlorinated species the enol form is strongly preferred.