Answer :
ethyne can be converted into propyne as follows :
LIQUID NH3 _ +
HC = CH + NaNH2 ---------------------> HC = C Na + NH3
196 K
_ +
HC = C Na + CH3 + Br --> HC = C - CH3 + NaBr
LIQUID NH3 _ +
HC = CH + NaNH2 ---------------------> HC = C Na + NH3
196 K
_ +
HC = C Na + CH3 + Br --> HC = C - CH3 + NaBr