Chemistry - GOC Question with Solution | TestHub

Terminal alkynes have ${\mathrm{pK}}_{\mathrm{a}}$ around 25, while ammonia has ${\mathrm{pK}}_{\mathrm{a}}$ about 38. Amide ion therefore removes the terminal proton and forms an acetylide. Liquid ${\mathrm{NH}}_3$ is a suitable medium for ${\mathrm{NaNH}}_2$. Water and ethanol protonate/consume amide and acetylide, preventing isolation of the stated product. Thus $\mathrm{B}$ is correct. ${\mathrm{NaHCO}}_3$ in the original equation was too weak a base and has been replaced, with the by-products balanced accordingly.