The reaction intermediates involved in the addition of HBr to propene in the presence of an organic peroxide are
(a) free radicals
(b)carbocations
(c)carbanions
(d)carbenes

Options

A. free radicals
B. carbocations
C. carbanions
D. carbenes

Explanation

To determine the reaction intermediates involved in the addition of HBr to propene in the presence of an organic peroxide, we can analyze the reaction mechanism step by step.

### Step 1: Understanding the Role of Organic Peroxides
Organic peroxides (R-O-O-R) undergo homolytic cleavage to form free radicals. This means that the bond between the oxygen atoms breaks evenly, resulting in two alkoxy radicals (R-O•).

**Hint:** Organic peroxides generate free radicals when they decompose.

### Step 2: Formation of Alkoxy Radicals
When the organic peroxide decomposes, it produces two alkoxy radicals (R-O•). These radicals are highly reactive and can initiate further reactions.

**Hint:** Look for the radicals produced from the cleavage of peroxides.

### Step 3: Reaction of Alkoxy Radicals with HBr
The alkoxy radical (R-O•) reacts with HBr. During this reaction, homolytic cleavage occurs again, resulting in the formation of an alcohol (ROH) and a bromine radical (Br•).

**Hint:** Identify how radicals interact with HBr to generate new radicals.

### Step 4: Addition of Bromine Radical to Propene
Now, we have propene (CH3-CH=CH2) and a bromine radical (Br•). The bromine radical will add to one of the carbons in the double bond. According to the anti-Markovnikov rule, the bromine radical will attach to the carbon that has more hydrogen atoms, leading to the formation of a new radical.

**Hint:** Remember the anti-Markovnikov rule when considering where the bromine radical will add.

### Step 5: Formation of the New Radical
After the bromine radical adds to propene, we form a new radical intermediate (the radical is now located on the carbon that was previously a double bond). This radical can further react with another molecule of HBr.

**Hint:** Recognize that the addition of radicals can create new radical intermediates.

### Step 6: Final Product Formation
The new radical formed will react with another HBr molecule, leading to the addition of a hydrogen atom to the radical site. This results in the formation of the final product, 1-bromopropane (CH3-CH2-CH2Br), and regenerates another bromine radical.

**Hint:** The final product is formed through the reaction of the radical with HBr.

### Conclusion
The entire reaction mechanism involves the formation and reaction of free radicals. Therefore, the correct answer to the question regarding the reaction intermediates involved in the addition of HBr to propene in the presence of an organic peroxide is:

**(a) free radicals**