• (iii) is actually the reaction Gabriel pthalimide synthesis

• Gabriel phthalimide synthesis is a chemical reaction that transforms primary alkyl halides into primary amines.

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generally, the reaction uses potassium pthalimide as reactant which by reaction with ethanolic KOH at first produces potassium salt of phthalimide which con heating with a certain alkyl halide(production of N-aikyl pthalimide) followed by hydrolysis in alkaline medium produces the corresponding primary amine, without changing in the number of carbon atoms of the chain.

Other options (i), (ii) and (iv) are not able to prepare of amines will give the same number of carbon atoms in the chain of amines as in the reactant.