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Generation of Fluorinated m ‐Benzyne Derivatives in Neon Matrices
Author(s) -
Wenk Hans Henning,
Sander Wolfram
Publication year - 2002
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/1099-0690(200212)2002:23<3927::aid-ejoc3927>3.0.co;2-r
Subject(s) - aryne , chemistry , radical , photodissociation , neon , trimethylsilyl , trifluoromethyl , singlet state , matrix isolation , photochemistry , intramolecular force , medicinal chemistry , computational chemistry , stereochemistry , infrared spectroscopy , organic chemistry , argon , excited state , alkyl , physics , nuclear physics
The fluorinated m ‐didehydrobenzenes 5‐H‐, 5‐deuterio‐, 5‐(trifluoromethyl)‐, 5‐(trimethylsilyl)‐, and 5‐iodo‐2,4,6‐trifluoro‐1,3‐didehydrobenzene 6b − 6f were generated by UV photolysis of the corresponding 1,3‐diiodobenzene derivatives 4b − 4f in solid neon at 3 K. The photolysis of 1 proceeds stepwise via the phenyl radical intermediates 5b − 5f . The radicals 5 and m ‐benzynes 6 were identified by comparison of their experimentally measured IR spectra with those produced by DFT calculations. The formation of mono‐ and diradicals 5 and 6 , respectively, is reversible, and annealing of the matrix at 7.5 K results in a decrease in all IR absorptions assigned to the radical products and in back‐formation of the diiodobenzenes. The influence of the substituents in the 5‐position on the geometries and the electronic structures of the diradicals 6 is discussed. The calculations indicate that the singlet‐triplet splittings of the substituted m ‐benzynes 6b − 6f are larger and the C 1 −C 3 distances shorter than those in the parent m ‐benzyne (C 6 H 4 ). (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)