The reaction between alcoholic KOH and alkyl halide is called the Williamson ether synthesis. In this reaction, an alkyl halide reacts with an alkoxide ion, which is generated by the reaction of an alcohol with KOH, to form an ether. The general equation for this reaction is:

```

RX + RO-K+ → ROR' + KX

```

where RX is the alkyl halide, RO-K+ is the alkoxide ion, ROR' is the ether, and KX is the salt byproduct.

The mechanism of the Williamson ether synthesis involves a nucleophilic substitution reaction. The alkoxide ion acts as a nucleophile and attacks the alkyl halide, displacing the halide ion and forming an ether. The reaction proceeds via an SN2 mechanism, which means that the reaction rate is dependent on the concentration of both the alkoxide ion and the alkyl halide.

The Williamson ether synthesis is a versatile reaction that can be used to synthesize a wide variety of ethers. It is commonly used in organic chemistry for the synthesis of symmetrical and unsymmetrical ethers. The reaction conditions are mild, and the yields are typically high.