$\underset{Alkyhalide}{\mathop{R-\,C{{H}_{2}}-C{{H}_{2}}-X}}\,\xrightarrow[Alc.KOH]{Dehydroha\log enation}$ $\underset{Alkene}{\mathop{R-\,CH=C{{H}_{2}}+HX}}$

$\underset{Alkyhalide}{\mathop{R-\,C{{H}_{2}}-C{{H}_{2}}-X}}\,\xrightarrow[Alc.KOH]{E\lim ination}$ $\underset{Alkene}{\mathop{R-\,CH=C{{H}_{2}}+HX}}$

$\underset{Alkyhalide}{\mathop{R-\,C{{H}_{2}}-C{{H}_{2}}-X}}\,\xrightarrow[substitution]{Aq.\,KOH}$  $\underset{Alcohol}{\mathop{R-\,C{{H}_{2}}-C{{H}_{2}}-OH+HX}}\,$