Which of the following will give positive tollen's test ?

Options

A. `CH_(3)-CH_(3)`
B. `CH_(2)=CH_(2)`
C. `CH-=CH`
D.

Answer

To determine which of the given compounds will give a positive Tollen's test, we need to follow these steps:

### Step 1: Understand Tollen's Test
Tollen's test is a qualitative test used to identify aldehydes and terminal alkynes. The reagent used is ammoniacal silver nitrate (Ag(NH3)2NO3). When aldehydes or terminal alkynes react with this reagent, they produce a characteristic silver mirror or a white precipitate, respectively.

### Step 2: Analyze the Given Compounds
The options provided are:
1. Ethane (C2H6)
2. Ethene (C2H4)
3. Ethyne (C2H2)
4. Benzene (C6H6)

### Step 3: Identify the Functional Groups
- **Ethane**: This is an alkane (C-C single bonds) and does not contain any functional groups that can react with Tollen's reagent.
- **Ethene**: This is an alkene (C=C double bonds) and also lacks the necessary functional groups for a reaction with Tollen's reagent.
- **Ethyne**: This is a terminal alkyne (C≡C triple bond with a hydrogen at one end). Terminal alkynes can react with Tollen's reagent to produce a white precipitate.
- **Benzene**: This is an aromatic hydrocarbon and does not react with Tollen's reagent.

### Step 4: Conclusion
Among the options, only **ethyne (C2H2)** will give a positive Tollen's test by forming a white precipitate (silver acetylide) when reacted with the Tollen's reagent.

### Final Answer
The compound that will give a positive Tollen's test is **Ethyne (C2H2)**.

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