The reaction,
$\mathrm{RX}+\mathrm{R}-\mathrm{ONa}⟶\mathrm{R}-\mathrm{O}-\mathrm{R}+\mathrm{NaX}$ is called

William son syntheisis is a General laboratory method used to prepare all kinds of ethers, symmetrical and unsymmetrical. It involves the reaction of RONa or ROK with alkyl halides and give ether. The order of R-X reactivity is Primary highest and tertiary the least. Tertiary RX will give alkenes as product.