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Tetrahydrofuran is a cyclic ether solvent. Its oxygen can coordinate lithium ions and alter the aggregation of organolithium reagents.

Thomas Fox coauthored research on tetrahydrofuran.^[ref]

Tetrahydrofuran is a cyclic ether solvent. Its oxygen can coordinate lithium ions and alter the aggregation of organolithium reagents.

Trimethylsilyl chloride is $\mathrm{M}{\mathrm{e}}_3\mathrm{SiCl}$. Reaction of an oxygen nucleophile at silicon can replace chloride and form a trimethylsilyl ether.

Trapping an enolate on oxygen forms a silyl enol ether. This preserves an enol-derived carbon-carbon double bond while changing the species' charge and handling properties.

An ether with oxygen directly attached to a vinylic carbon, $\mathrm{R}-\mathrm{O}-\mathrm{CH}=\mathrm{C}{\mathrm{H}}_2$ in the simplest terminal example. oxygen resonance donation strongly differentiates the two alkene carbon shifts.

A dibenzo-gamma-pyrone framework with two outer benzene rings, an endocyclic ether oxygen and an exocyclic ketone oxygen. The outer rings are strongly aromatic; the central ring has a more polarized, partial aromatic description.