Vibrational spectrum of m-benzyne: a matrix isolation and computational study.
m-Benzyne (2) was generated in low-temperature matrices and IR spectroscopically characterized from four different precursors. To assign the IR absorptions, the perdeuterated derivative 2-d(4) was also investigated. By comparison with CCSD(T) calculations all vibrations between 200 and 2500 cm(-)(1) with a predicted relative intensity >2% could be assigned. All experimental and theoretical results are in accordance with a biradicaloid structure for 2, while there is no evidence for a bicyclic closed-shell structure. While benzyne 2 is stable under the conditions of matrix isolation at low temperature, flash vacuum pyrolysis at high temperatures or UV irradiation results in the rearrangement to cis-enediyne. A mechanism involving ring opening accompanied by hydrogen migration is proposed.
Sander
Wolfram
W
Lehrstuhl für Organische Chemie II der Ruhr-Universität, D-44780 Bochum, Germany.
Exner
Michael
M
Winkler
Michael
M
Balster
Andreas
A
Hjerpe
Angelica
A
Kraka
Elfi
E
Cremer
Dieter
D