How many of the following compounds will form acetic acid on reaction with acidic `KMnO_(4)` ?
Prop-1- ene, 2-Methylbut-2-ene, 2- Methylpropene,But-2-ene, Cyclohexene.

Answer

To determine how many of the given compounds will form acetic acid upon reaction with acidic KMnO4, we need to analyze each compound based on the oxidation reaction with KMnO4, a strong oxidizing agent.

### Step-by-Step Solution:

1. **Identify the Compounds**:
- Prop-1-ene: CH3-CH=CH2
- 2-Methylbut-2-ene: CH3-C(CH3)=CH2
- 2-Methylpropene: CH3-C(CH3)=CH2
- But-2-ene: CH3-CH=CH-CH3
- Cyclohexene: C6H10 (a cyclic alkene)

2. **Understand the Reaction with KMnO4**:
- KMnO4 cleaves the double bond in alkenes and converts the carbon atoms involved in the double bond to carboxylic acids (COOH) if they contain hydrogen atoms.
- If one of the carbons in the double bond does not have a hydrogen atom, it will be converted to a ketone instead.

3. **Analyze Each Compound**:
- **Prop-1-ene (CH3-CH=CH2)**:
- The double bond is between CH3 and CH2. The carbon in CH2 has a hydrogen. Thus, it will form acetic acid (CH3COOH) and formic acid (HCOOH), which decomposes to CO2.
- **2-Methylbut-2-ene (CH3-C(CH3)=CH2)**:
- The double bond is between the carbon with CH3 and CH2. The CH2 has a hydrogen, leading to the formation of acetic acid (CH3COOH) from one side and a ketone from the other side.
- **2-Methylpropene (CH3-C(CH3)=CH2)**:
- Similar to the previous compound, the double bond involves a carbon with a hydrogen (CH2), leading to the formation of acetic acid (CH3COOH) and a ketone from the other side.
- **But-2-ene (CH3-CH=CH-CH3)**:
- The double bond is between two carbons that both have hydrogen atoms. This will also lead to the formation of acetic acid (CH3COOH) from both sides.
- **Cyclohexene (C6H10)**:
- The double bond is between two carbons in a cyclic structure, both of which have hydrogen atoms. This will also lead to the formation of carboxylic acids from both sides.

4. **Count the Compounds that Form Acetic Acid**:
- **Prop-1-ene**: Forms acetic acid.
- **2-Methylbut-2-ene**: Forms acetic acid.
- **2-Methylpropene**: Forms acetic acid.
- **But-2-ene**: Forms acetic acid.
- **Cyclohexene**: Forms acetic acid.

### Conclusion:
All five compounds will form acetic acid upon reaction with acidic KMnO4.

**Final Answer**: 5 compounds will form acetic acid.