Equilibrium structure of maleic anhydride from gas-phase electron diffraction (GED) and quantum-chemical studies

✍ Scribed by Natalja Vogt; Ekaterina P. Altova; Nikolai M. Karasev

• Publisher: Elsevier Science
• Year: 2010
• Tongue: English
• Weight: 365 KB
• Volume: 978
• Category: Article
• ISSN: 0022-2860
• DOI: 10.1016/j.molstruc.2010.02.037

✦ Synopsis

Thermal-average and equilibrium molecular structure Gas-phase electron diffraction Anharmonic corrections to experimental bond lengths and rotational constants Quantum-chemical calculations of structure and force field a b s t r a c t

The molecular structure of maleic anhydride was reinvestigated by the gas-phase electron diffraction (GED) method because it was determined with large uncertainties in a previous study. To take into account vibrational effects, the corrections to the experimental bond lengths (r a ) were calculated using quadratic and cubic force constants from high-level ab initio calculations (MP2/aug-cc-pVTZ). The determined equilibrium structural parameters (r e (C-C) = 1.485(1) Å, r e (C@C) = 1.332(1) Å, r e (C-O) = 1.386(1) Å, r e (C@O) = 1.192(1) Å, \ e (C-C@C) = 107.8(1)°, \ e (O@C-C) = 129.2(2)°) are very close to the parameters of the r s structure from a previous microwave spectroscopic (MW) study. Some aspects of the combined analysis of GED and MW data are discussed. The agreement of the experimental rotational constants, B ðiÞ 0 (MW), corrected for anharmonic effects, B ðiÞ e (MW), with the rotational constants derived from the determined equilibrium geometry, is better than with B ðiÞ e values from quantum-chemical calculations.