Question

Which of the following alkyl halide produces white precipitate of AgCl most readily
on reaction with aqueous AgNO,?
:ci:
CHCI
CHCI
8
(2)
(3)
(4)
OCH
NO.​

Answer 1

Answer:

Silver nitrate solution can be used to find out which halogen is present in a suspected halogenoalkane. The most effective way is to do a substitution reaction which turns the halogen into a halide ion, and then to test for that ion with silver nitrate solution.

The halogenoalkane is warmed with some sodium hydroxide solution in a mixture of ethanol and water. Everything will dissolve in this mixture and so you can get a good reaction. The halogen atom is displaced as a halide ion:

R−X+OH−→R−OH+X−(1)

with X is any haligen atom.

The tertiary halide produces a precipitate almost instantly.

The secondary halide gives a slight precipitate after a few seconds. The precipitate thickens up with time.

The primary halide may take considerably longer to produce a precipitate.

It is more difficult to explain the reason for this, because it needs a fairly intimate knowledge of the mechanisms involved in the reactions. It reflects the change in the way that the halide ion is produced as you go from primary to secondary to tertiary halogenoalkanes.

Answer 2

Answer:

CH2=CHCH2Cl is allyl chloride, which when combined with cold AgNO3 produces a white precipitate of AgCl.

Explanation:

• A suspected halogenoalkane can be examined with a silver nitrate solution to determine which halogen is present. The best method is to perform a substitution process that converts the halogen into a halide ion, and then use silver nitrate solution to check for that ion.
• R−X+OH−→R−OH+X−
• Warm sodium hydroxide solution is added to a mixture of ethanol and water to warm the halogenoalkane. In this mixture, everything will dissolve, allowing for a favorable reaction.
• The silver nitrate test is sensitive enough to pick up halide ions at relatively low quantities. Nitric acid solution is added to the mixture to make it acidic. By doing this, unreacted hydroxide ions are kept from interacting with the silver ions. Next, a solution of silver nitrate is added.

#SPJ2