ArylCHCHPh

ArylCHCHPh is a shorthand motif used in organic chemistry to denote a structural fragment in which two aryl groups are connected by a two-carbon core. The exact nature of the two-carbon linkage can vary with context: in many descriptions the fragment is intended as Ar-CH-CH-Ph, a diarylethane-type skeleton with a single carbon–carbon bond, while in other contexts the same notation may imply a vinyl linkage such as Ar-CH=CH-Ph (a stilbene skeleton). The term emphasizes the presence of an aryl group on each end of the two-carbon bridge and a CH or CH– unit in the middle.

Structure and stereochemistry: If the bridge is a single C–C bond (diarylethane), rotation about the bond can lead to different conformers, and in suitably substituted systems this rotation can be hindered enough to generate conformational or atropisomeric separation. If the bridge is a double bond (stilbene-like), geometric isomerism (E/Z) is typically present, with trans (E) isomer usually favored in simple cases due to lower steric hindrance and greater planarity, enabling extended conjugation between the two aryl rings.

Occurrence and significance: Motifs of this type are common in natural products, dyes, liquid crystals, and organic electronic materials. Stilbene derivatives are notable for their extended π-conjugation and have applications in nonlinear optics and photoresponsive systems. Diarylethanes appear in various synthetic targets and can serve as precursors to more complex biaryl structures.

Synthesis and reactivity: General approaches to building Ar–CH–CH–Ar frameworks include cross-coupling strategies that assemble the two aryl fragments with a two-carbon linker, as well as redox- or cycloaddition-based methods to install the CH–CH unit. Reactions of this motif can involve electrophilic aromatic substitution, hydrogenation to the saturated diarylethane, or oxidation to the stilbene variant.

See also: stilbene, diarylethane, biaryl compounds.