$C{H_2} = C{H_2}\xrightarrow{{B{r_2}}}\mathop {C{H_2}}\limits_{\mathop {|\,\,{\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} }\limits_{Br\,\,\,\,{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} } }  - \mathop {C{H_2}}\limits_{\mathop {|{\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} {\kern 1pt} \,\,}\limits_{Br{\mkern 1mu} {\mkern 1mu} {\mkern 1mu} {\mkern 1mu} \,\,\,\,} } \mathop {\xrightarrow{{alc.}}}\limits_{KOH} $

$\mathop {CH \equiv CH}\limits_{{\text{Acetylene}}}  + 2KBr + 2{H_2}O$