Matrix isolation spectroscopy is a viable tool for the isolation and characterization of free radicals. In inert media (in particular, rare gases such as argon or neon) at cryogenic temperatures (below 30 K), radicals are immobilized and kinetically stabilized. In some cases, it was also possible to investigate bimolecular reactions of matrix‐isolated radicals with small molecules. The spectroscopic characterization of simple alkyl radicals such as methyl and ethyl, of unsaturated radicals such as allyl and vinyl, and of aromatic radicals is described here.
Matrix isolation spectroscopy is a viable tool for the isolation and characterization of free radicals. In inert media (in particular, rare gases such as argon or neon) at cryogenic temperatures (below 30 K), radicals are immobilized and kinetically stabilized. In some cases, it was also possible to investigate bimolecular reactions of matrix‐isolated radicals with small molecules. The spectroscopic characterization of simple alkyl radicals such as methyl and ethyl, of unsaturated radicals such as allyl and vinyl, and of aromatic radicals is described here.
The phenyl radical (C 6 H 5 C) is the prototypical s-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-C ipso -C bond angle [125.8(3)8 vs. 1208], and a shorter distance [2.713(3) vs. 2.783 (2) ] between the ipso and para carbon atoms.
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.
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