The equilibrium structure of trans-glyoxal from experimental rotational constants and calculated vibration–rotation interaction constants

Abstract

A total of six high-resolution FT-IR spectra for trans-glyoxal-d₂, trans-glyoxal-d₁ and trans-glyoxal-¹³C₂ were recorded with a resolution ranging from 0.003 to 0.004 cm⁻¹. By means of a simultaneous ground state combination difference analysis for each of these isotopologues using the Watson Hamiltonian in A-reduction and I^r-representation the ground state rotational constants are obtained. An empirical equilibrium structure is determined for trans-glyoxal using these experimental ground state rotational constants and vibration–rotation interaction constants calculated at the CCSD(T)/cc-pVTZ level of theory. The least-squares fit yields the following structural parameters for trans-glyoxal: r_e(C–C) = 1.51453(38) Å, r_e(C–H) = 1.10071(26) Å, r_e(CO) = 1.20450(27) Å, α_e(CCH) = 115.251(24)°, and α_e(HCO) = 123.472(19)° in excellent agreement with theoretical predictions at the CCSD(T)/cc-pVQZ level of theory.