o-Phenylene halocarbenonitrenes and o-phenylene chlorocarbenocarbene: A combined experimental and computational approach
Date
2005Author
Enyo, T.Arai, N.
Nakane, N.
Nicolaïdes, Andrew N.
Tomioka, H.
Source
Journal of Organic ChemistryVolume
70Issue
19Pages
7744-7754Google Scholar check
Keyword(s):
Metadata
Show full item recordAbstract
Computations find that o-phenylene(halo)carbenonitrenes 2-XN, X = F, Cl, Br, have quinoidal singlet biradical ground states such as the parent o-phenylenecarbenonitrene (2-HN). Compared to the parent 2-HN, halogen substitution stabilizes the A″ states relative to the A′ ones. Halogen substitution also affects the barrier and exothermicity of the ring-opening reaction (to form unsaturated nitriles 4-XN, X = F, Cl, Br), but it has a smaller effect on the ring-closing reaction (to form benzo(aza) cyclobutadiene 3-XN, X = F, Cl, Br). Attempts to generate and observe the o-phenylene(halo)carbenonitrenes 2-XN, X = F, Cl, Br, using matrix isolation spectroscopy under conditions similar to those of the successful observation of 2-HN failed. Instead, the observed photoproducts were a mixture of 3-XN and 4-XN. In each case, the major product of the mixture appears to be the thermodynamically more stable one. In the case of X = Br, the observed mixture contains an additional component that is postulated to be Z-6-BrN. o-Phenylenechlorocarbenocarbene is also computed to have a quinoidal singlet biradical ground state and relatively stabilized A″ excited states. Attempts to generate the biscarbene under matrix isolation conditions led to the detection of benzochlorocyclobutadiene (3-ClC), small amounts of the ring-open product (dienediyne 4-ClC), and cycloalkyne 5-ClC. Computations suggest that the formation of 5-ClC implies the generation of Z-6-ClC, which is analogous to the formation of Z-6-BrN from 2-BrN. © 2005 American Chemical Society.
Collections
Cite as
Related items
Showing items related by title, author, creator and subject.
-
Article
Rates of activation and scanning electron microscopy of polyarylamide-derived chars
Tomlinson, J. B.; Freeman, J. J.; Sing, K. S. W.; Theocharis, Charis R. (1995)Fibrous activated carbons were prepared from Kevlar® (poly (p-phenylene terephthalamide)) and Nomex® (poly (m-phenylene isophthalamide)) by carbonisation in nitrogen and subsequent activation in steam of carbon dioxide to ...
-
Article
Halogen derivatives of m-phenylene(carbeno)nitrene: A switch in ground-state multiplicity
Enyo, T.; Nicolaïdes, Andrew N.; Tomioka, H. (2002)m-Phenylene-coupled carbenonitrenes [(3-nitrenophenyl)methylene (2-H), (3-nitrenophenyl)fluoromethylene (2-F), (3-nitrenophenyl)chloromethylene (2-Cl), (3-nitrenophenyl)bromomethylene (2-Br)] have been investigated ...
-
Article
Adsorption of nitrogen and water vapour by activated Nomex® chars
Freeman, J. J.; Tomlinson, J. B.; Sing, K. S. W.; Theocharis, Charis R. (1995)Fibrous activated carbons were prepared from Nomex® poly(m-phenylene isophthalamide), in the form of a commercially available woven textile. After carbonisation in nitrogen and activation in either carbon dioxide or steam ...