The Markovnikov rule is best applicable to the reaction between

Options

A. `C_2H_4+HCl`
B. `C_3H_6+Br_2`
C. `C_3H_6+HBr`
D. `C_3H_8+Cl_2`

Explanation

To answer the question regarding the applicability of the Markovnikov rule, we can follow these steps:

### Step 1: Understand the Markovnikov Rule
The Markovnikov rule states that when an unsymmetrical alkene reacts with a protic acid (like HCl, HBr, or HI), the hydrogen atom from the acid will attach to the carbon atom of the alkene that has the greater number of hydrogen atoms already attached. This results in the formation of the more stable carbocation intermediate.

### Step 2: Identify the Reaction Type
The Markovnikov rule is primarily applicable to the addition reactions of hydrogen halides (HX) to alkenes. In these reactions, the alkene acts as a nucleophile and attacks the electrophilic hydrogen of the acid.

### Step 3: Consider Examples
For example, when propene (an unsymmetrical alkene) reacts with HBr, the hydrogen will add to the carbon with more hydrogen atoms (the terminal carbon), leading to the formation of isopropyl bromide rather than n-propyl bromide.

### Step 4: Conclusion
Thus, the Markovnikov rule is best applicable to the reaction between unsymmetrical alkenes and hydrogen halides (HX).

### Final Answer
The Markovnikov rule is best applicable to the reaction between unsymmetrical alkenes and hydrogen halides (like HCl, HBr, or HI).

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