1) we can convert 1- pentyne to pentanal by adding H2SO4 and HgSO4 at 60 C°.
2)Then we make oxidation by KMnO4 to convert pentanal to pentanoic acid.
3) Finally, We add ethylamine and heat to obtain N-ethyl pentanamide.
Note: please find the attached photo as I have used ChemDraw program to draw the reactions.
