Tenmembered

Ten-membered refers to chemical species containing a ten-atom ring in their core structure. Ten-membered rings are classified as medium-sized rings, larger than common cycloalkanes such as cyclooctane but smaller than macrocycles typically defined as twelve or more atoms. The term applies to carbocyclic rings such as cyclodecane as well as heterocyclic rings in which one or more carbon atoms are replaced by heteroatoms such as oxygen, nitrogen, or sulfur.

Ten-membered rings are flexible and adopt nonplanar conformations that help minimize strain; transannular interactions can be significant and influence reactivity and selectivity. Ring strain in ten-membered rings is generally lower than in smaller rings but higher than in larger rings, contributing to challenges in synthesis and conformational control. Substitution and the presence of heteroatoms further modify strain and conformational preferences.

The unsubstituted carbocycle cyclodecane (C10H20) is a canonical example and exists in multiple rapidly interconverting conformers. Ten-membered heterocycles occur in natural products and synthetic ligands, including oxacycles, azacycles, and thia- and selenacycles, where the ring geometry constrains binding interactions. Ten-membered rings also appear in small macrocyclic lactams and lactones used in medicinal chemistry and materials science.

Synthesis of ten-membered rings commonly uses intramolecular cyclization strategies such as ring-closing metathesis, lactamization, or cycloaddition under high-dilution conditions to favor cyclization over polymerization. Strategies to reduce entropic penalties include preorganization, tethered precursors, or templating by metal ions or noncovalent interactions.

See also cyclodecane, medium-ring chemistry, macrocycle.

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