Which of the following is a free radical substitution reaction?

Options

A.
B.
C.
D. `CH_3CHO+HCN to CH_3CH(OH)CN`

Answer

To determine which of the given options is a free radical substitution reaction, we need to follow a systematic approach:

### Step 1: Understand Free Radical Substitution Reactions
Free radical substitution reactions typically occur under specific conditions, such as:
- Presence of heat or light
- Presence of peroxides (like H2O2)
- Presence of free radicals
- Under electrical influence (like electrolysis)

### Step 2: Analyze the Options
Without the specific options provided in the question, we will assume that one of the options mentions the presence of light.

### Step 3: Identify the Correct Option
If one of the options indicates that the reaction occurs in the presence of light, this is a strong indicator that it is a free radical substitution reaction.

### Step 4: Confirm the Mechanism
In reactions involving light, the energy from light can initiate the formation of free radicals, which can then lead to substitution reactions.

### Conclusion
Based on the analysis, if option D mentions light, then it is the correct answer for a free radical substitution reaction.

### Final Answer
The correct option indicating a free radical substitution reaction is **D (if it mentions light)**.

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