Dehydrohalogenation of Dihalides

$$\begin{aligned}\text{R--CHX--CH}_2\text{X} \xrightarrow{\text{Alc. KOH, } \Delta} \text{R--C(X)=CH}_2 \xrightarrow{\text{NaNH}_2} \text{R--C}\equiv\text{CH}\end{aligned}$$

Concept: Vicinal or geminal dihalides undergo stepwise double elimination of hydrogen halide ($$\text{HX}$$) to introduce a triple bond.