Gabriel phthalimide synthesis can be used to prepare which of the following compounds
A) ethanamine
B) n methylmethanamine
C) benzene amine
D) N,N,-dimethylmethanamine
E )p-toluidine

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Hint: Gabriel phthalimide synthesis is used to prepare aliphatic primary amines $({\text{R - $NH_2$}})$ from primary alkyl halides ${\text{(R - X)}}$ . Primary amines are those compounds which have one alkyl group (R) and two hydrogens attached to the nitrogen.

Complete answer:Let us first write the chemical formulae of all the compounds given in the question:
$1.$ The chemical formula of ethanamine will be ${\text{$C_2H5$ - $NH_2$}}$ .
$2.$ The chemical formula of n methylmethanamine will be ${\text{$(CH_3)_2$ - NH}}$ .
$3.$ The chemical formula of benzylamine will be ${\text{$C_6H_5$ - $NH_2$}}$ .
$4.$ The chemical formula of N,N,-dimethylmethanamine will be ${\text{($CH_3)_3$ - N}}$ .
$5.$ The chemical formula of p-toluidine will be ${\text{$CH_3$ - $C_6H_4$ - $NH_2$}}$ .
As is clear that benzene amine and p-toluidine are aromatic compounds, thus, options ‘C’ and ‘E’ are ruled out.
Among ethanamine, n methylmethanamine and N,N,-dimethylmethanamine, the primary amine is ethanamine only.
Hence, the correct option is ‘A’.

Additional information: Gabriel phthalimide synthesis is named after the German chemist Siegmund Gabriel. In this reaction, a potassium or sodium salt of phthalimide is reacted with an alkyl halide to form N-alkylated phthalimide which is then reduced using hydrazine hydrate to give primary amine as the final product. This is a very selective reaction for the synthesis of primary amines as the nitrogen is protected by two bonds in the phthalimide and only one site is open to react with the alkyl halide. The protected sites of nitrogen are then reduced by the addition of hydrogen to give primary amines exclusively.

Always first write the chemical formula of the given compounds and find out the compound which is a primary amine. It is important to note that Gabriel phthalimide synthesis is only for aliphatic amines and not for aromatic amines.