Due to the high chemical stability of ethers, the cleavage of the C-O bond is uncommon in the absence of specialized reagents or under extreme conditions.
Distinguishing between both mechanisms requires consideration of inductive and mesomeric effects that could stabilize or destabilize a potential carbocation in the SN1 pathway.
Usage of hydrohalic acids takes advantage of the fact that these agents are able to protonate the ether oxygen atom and also provide a halide anion as a suitable nucleophile.
However, reactions that would require the formation of unstable carbocations (methyl, vinyl, aryl or primary carbon) proceed via SN2 mechanism.
The formed hydride then attacks the olefinic rest in α position to the ether oxygen, releasing the alkoxide.
Organometallic agents are often handled in etheric solvents, which coordinate to the metallic centers and thereby enhance the reactivity of the organic rests.