64) Ethyne can be prepared in a single step from:

65) 2,3−dibromobutane, when heated with zinc dust yields:

66) An aqueous solution of patassium salt of fumaric acid is electrolysed. The hydrocarbon produced at the anode is:

67) 2−pentyne can be converted into trans−pent−2−ene by reaction with:

68) How many different isomeric compounds having molecular formula C₅H₁₁Br on reaction with Mg, followed by hydrolysis can yield pentane?