An Accurate Molecular Structure of Phenyl, the Simplest Aryl Radical

The phenyl radical (C6H5.) is the prototypical σ‐type aryl radical and one of the most common aromatic building blocks for larger ring molecules. Using a combination of rotational spectroscopy of singly substituted isotopic species and vibrational corrections calculated theoretically, an extremely accurate molecular structure has been determined. Relative to benzene, the phenyl radical has a substantially larger C‐Cipso‐C bond angle [125.8(3)° vs. 120°], and a shorter distance [2.713(3) Å vs. 2.783(2) Å] between the ipso and para carbon atoms. Radical structure: Using a combination of rotational spectroscopy and vibrational corrections calculated theoretically, an extremely accurate molecular structure of the phenyl radical has been determined. Relative to benzene, the phenyl radical has a substantially larger C‐Cipso‐C bond angle (125.8(3)° vs. 120°), and a shorter distance (2.713(3) Å vs. 2.783(2) Å) between the ipso and para carbon atoms.