Question

What changes are observed when the following reagents are added to alkanes, alkenes and alkynes? Write your answer in a tabular form. Reagents : (i) Bromine in CCl

4
​
(ii) Baeyer's reagent (iii) Ammoniacal solution of AgNO
3
​
and (iv) Ammoniacal solution of Cu
2
​
Cl
2
​
C

Answer 1

Alkanes are generally inert to the given reagents under normal conditions, while alkenes and alkynes show discoloration with bromine in CCl4 and Baeyer's reagent, indicating addition reactions. Alkynes also form precipitates with ammoniacal AgNO3 and Cu2Cl2.

Step-by-step explanation:

Reactions of Hydrocarbons with Specific Reagents

Here are the typical reactions observed when specific reagents are added to alkanes, alkenes, and alkynes:

HydrocarbonBromine in CCl4Baeyer's reagentAmmoniacal AgNO3Ammoniacal Cu2Cl2

Alkanes

No reaction (under normal conditions)No reactionNo reactionNo reaction

Alkenes

Decolorization of bromine, indicating addition across the double bondDecolorization indicating the oxidation of the double bondNo reactionNo reaction

Alkynes

Decolorization of bromine, indicating addition across the triple bondDecolorization indicating the oxidation of the triple bondA precipitate of silver acetylide is formedA precipitate of copper acetylide is formed

Let's discuss these observations:

• Alkanes show very little reactivity with these reagents under normal conditions since they have only single bonds which are relatively inert to addition reactions.
• Alkenes undergo addition reactions as they have a double bond that can react with bromine (as in bromination) and can be oxidized by Baeyer's reagent (dilute KMnO4), resulting in the disappearance of their respective colors.
• Alkynes, with their triple bonds, also undergo addition reactions with bromine and are oxidized by Baeyer's reagent. Furthermore, alkynes form precipitates when treated with ammoniacal solutions of AgNO3 or Cu2Cl2 due to the formation of silver or copper acetylides, respectively.

Answer 2

We can see here:

Bromine in
`CCl_(4)`

Alkanes: No reaction (No color change observed)

Alkenes: Decolorizes bromine solution (from red to colorless)

Alkynes: No reaction (No color change observed)

Baeyer's reagent

Alkanes: No reaction (No color change observed)

Alkenes: Forms a colored complex or precipitate

Alkynes: Forms a colored complex or precipitate

Ammoniacal of
`AgNO_(3)`

Alkanes: No reaction (No color change observed)

Alkenes: Forms a silver mirror (Silver mirror test)

Alkynes: No reaction (No color change observed)

Ammoniacal of
`CuCl_(2)`

Alkanes: No reaction (No color change observed)

Alkenes: No reaction (No color change observed)

Alkynes: Reddish-brown or reddish-orange precipitate is formed.

Alkanes are a type of hydrocarbon, which means they consist solely of hydrogen and carbon atoms bonded together in a specific manner.