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How does adding water to ethylene produce ethanol?

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dissociation of E–N — reaction mechanism Possible energy diagram for the dissociation of a covalent molecule, E–N, into its ions E⁺ and N⁻ (see text).

The production of ethanol from ethylene is achieved through a process known as hydration, which is a type of addition reaction.

In this industrial process, a mixture of ethylene and a large excess of steam is passed over an acidic catalyst at high temperature and pressure. The reaction involves the addition of water across the carbon-to-carbon double bond of the ethylene molecule. By breaking the double bond, the molecule is able to accommodate the additional atoms from the water molecule, resulting in the formation of ethanol ( $C_{2} H_{5} O H$ ).123

While many alkene hydrations follow the Markovnikov rule—where the hydroxyl group attaches to the more highly substituted carbon—ethylene is a symmetric molecule, meaning the hydroxyl group can add to either carbon atom to produce the same product.2