orthophenylenediyl

Orthophenylenediyl, or o-phenylene-1,2-diyl, is a divalent aryl fragment derived from benzene by removing two adjacent hydrogen atoms at the 1,2-positions. As such, it represents a reactive arylene unit that can function as a diyl (two attachment points) or as a short-lived diradical intermediate in organic reactions. In structural terms the unit is a benzene ring bearing two neighboring open valences, which may be realized as a singlet or triplet species depending on substitution and environment.

In practice orthophenylenediyl is typically generated or trapped as a transient intermediate. It is studied in matrix isolation, low-temperature experiments, and through the use of stabilizing substituents or protective groups that prevent rapid dimerization or rearrangement. It can also act as a bridging fragment that links two aryl groups, yielding ortho-linked diaryl systems in synthetic routes to polyarylenes and related materials.

Because of its high reactivity, the orthophenylenediyl is mainly of interest in physical organic chemistry and materials science, where it serves as a conceptual model for understanding the behavior of arylene diradicals and as a building block in designing rigid, planar conjugated frameworks. Related concepts include phenylene, arylene, and xylylene species, and the study of such 1,2-diyl fragments informs approaches to controlled assembly of aromatic polymers.