Gas Electron Diffraction and Quantum-Mechanical Study of Dimethyloxalate

Authors: Vishnevskiy Yu.¹; Ivanov A.¹; Oberhammer H.¹; Vilkov L.²

Source: Structural Chemistry, Volume 16, Number 1, February 2005 , pp. 41-46(6)

Publisher: Springer

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Abstract:

The geometrical structure and conformation of dimethyloxalate, CH₃OC(O)–C(O)OCH₃, have been studied by gas electron diffraction (GED) and quantum-chemical calculations (MP2 and B3LYP methods with 6-31G* and cc-pVTZ basis sets). The GED analysis with a dynamic model (T = 323 K) results in a mixture of two planar conformers, anti (C_2h symmetry) and syn (C_2v symmetry) orientation of the two C=O bonds. The energy difference between these conformers is 0.02(0.18) kcal/mol and barrier to internal rotation around the C–C bond is 0.44(0.41) kcal/mol. The CH₃ groups occupy synperiplanar positions with respect to the C=O bonds. The following main geometrical parameters for the anti conformer (Å and degrees) have been derived: r_g(C–C) = 1.532(3), r_g(C=O) = 1.203(2), r_g(C_sp3–O) = 1.436(3), r_g(C_sp2–O) = 1.333(3), ang

(C_sp2–C_sp2–O) = 111.9(1.9), ang

(C_sp2–O–C_sp3) = 116.3(1.6), ang

(O–C= O) = 127.0(1.8).

Keywords: Dimethyloxalate; gas electron diffraction; ab initio and DFT calculations

Document Type: Research article

DOI: http://dx.doi.org/10.1007/s11224-005-1079-y

Affiliations: 1: Department of Chemistry, Moscow State University, Moscow, 119899, Russia, 2: Department of Chemistry, Moscow State University, Moscow, 119899, Russia, Email: lvvilkov@phys.chem.msu.ru

Publication date: 2005-02-01