Question

Statement: The reagents \[{\text{NaN}}{{\text{H}}_{\text{2}}}\] and excess of chlorine are required to prepare 1,1,2,2-tetrachloropropane from 1,2-dichloropropane.
If the given statement is true enter 1 if false enter 0.

Answer 1

Hint: Alkynes are prepared by dehydrohalogenation of dihalogen derivatives of alkanes in presence of a strong base. Alkynes on halogenation gives tetra halogen derivatives.

Complete step by step answer:
You can classify halogen derivatives of alkanes into mono halogen derivatives, di halogen derivatives, tri halogen derivatives, tetra halogen derivatives and poly halogen derivatives. mono halogen derivatives, di halogen derivatives, tri halogen derivatives, tetra halogen derivatives and poly halogen derivatives of alkanes contain one, two, three, four and several halogen atoms. Halogen can be either fluorine or chlorine or bromine or iodine.
\[{\text{NaN}}{{\text{H}}_{\text{2}}}\] is soda amide. It is a strong base. It is used for the dehydrohalogenation of haloalkanes. During dehydrohalogenation, hydrogen halide molecules are eliminated and carbon-carbon multiple bonds are obtained. Mono halogen derivative of alkane loses one molecule of hydrogen halide and forms an alkene. Dihalogen derivative of alkane loses two molecules of hydrogen halide and forms an alkyne.
1,2-dichloropropane is the dichloro derivative of alkane. When 1,2-dichloropropane is treated with \[{\text{NaN}}{{\text{H}}_{\text{2}}}\] , it loses two molecules of hydrogen chloride to form propyne (an alkyne).

When propyne is treated with excess chlorine, 1,1,2,2-tetrachloropropane is obtained. Two chlorine molecules are added to \[{\text{C}} \equiv {\text{C}}\] triple bond.

Thus, when 1,2-dichloropropane reacts with \[{\text{NaN}}{{\text{H}}_{\text{2}}}\] and excess of chlorine, the product obtained is 1,1,2,2-tetrachloropropane.

Hence, the given statement is true. So, enter 1.

Note: Soda amide can also be used to abstract the most acidic proton of terminal alkynes. When a terminal alkyne loses an acidic proton, it forms an acetylide ion. This acetylide ion acts as a nucleophile and can attack carbonyl compounds to form carbon-carbon bonds.