The molecular structure of ortho- and meta-fluorobenzaldehyde by joint analysis of gas electron diffraction, microwave spectroscopy and ab initio molecular orbital calculations

Abstract The molecular structures of gaseous o -fluorobenzaldehyde and m -fluorobenzaldehyde have been determined by a joint analysis of gas electron diffraction data, rotational constants from microwave spectroscopy, and constrained by results from ab initio calculations (at HF/6-331G∗∗ level). The torsion of the formyl group has been treated as a large-amplitude motion. The most important structure parameters ( r g )) from the joint analysis with estimated total errors (in parentheses) are for o -fluorobenzaldehyde: ( C  C ) mean = 1.3999(2) A , C  F = 1.334(5) A , C  C ( O = 1.515(6) A , C  O = 1.216(3) A , ∠CC F C = 122.0(2)°, ∠CC CHO C = 120.3(6)° and for m -fluorobenzaldehyde: ( C  C ) mean = 1.394(2) A , C  F = 1.346(4) A , C  C ( O = 1.494(4) A , C  O = 1.201(2) A , ∠CC F C = 122.3(1)°, and ∠CC CHO C = 120.6(3)°. The scaled molecular force fields have been determined.