Dilute aqueous `KMnO_4` at room temperature reacts with R-CH=CH-R to give

Options

A. `R - CHO`
B. `R - COOH`
C. `RCHOH - CHOHR`
D. `CO_2 + H_2O`

Answer

To solve the problem, we need to understand the reaction of dilute aqueous KMnO4 with an alkene (R-CH=CH-R). This reaction is commonly known as the Baeyer's test for unsaturation.

### Step-by-Step Solution:

1. **Identify the Reactant**: The reactant is an alkene represented as R-CH=CH-R, where R can be any organic group.

2. **Understand the Reagent**: Dilute aqueous KMnO4 is known as Baeyer's reagent. It is used to oxidize alkenes.

3. **Reaction Mechanism**: When the alkene reacts with dilute KMnO4, the double bond (C=C) is oxidized. The reaction involves the addition of hydroxyl (–OH) groups across the double bond.

4. **Product Formation**: The result of this reaction is the formation of a diol (glycol), specifically a vicinal diol where two hydroxyl groups are added to the adjacent carbon atoms. The structure of the product will be R-CHOH-CHOH-R.

5. **Conclusion**: Therefore, the product formed from the reaction of R-CH=CH-R with dilute aqueous KMnO4 is R-CHOH-CHOH-R, which corresponds to option 3.

### Final Answer:
The correct answer is option 3: R-CHOH-CHOH-R.