`CH_(3)-overset(O)overset(||)(C)-CH_(3)overset(X_(2))underset(OH^(ɵ))toCHX_(3)+CH_(3)-overset(O)overset(||)(C)-O^(ɵ)`
The rate of haloform reaction reaction is fastest with

Options

A. `X_(2)=Cl_(2)`
B. `X_(2)=Br_(2)`
C. `X_(2)=I_(2)`
D. All at same rate `r_(Cl_(2))=r_(Br_(2))=r_(I_(2))`

Explanation

To solve the question regarding the rate of the haloform reaction, we need to understand the mechanism and factors affecting the reaction rate. Here’s a step-by-step solution:

### Step 1: Understand the Haloform Reaction
The haloform reaction involves the conversion of a methyl ketone (such as acetone) into a haloform (like iodoform, chloroform, or bromoform) in the presence of halogens (X₂) and a base (like NaOH). The general reaction can be represented as:

\[ RCOCH_3 + 3X_2 + 4NaOH \rightarrow RCOONa + 3NaX + CHX_3 + 3H_2O \]

### Step 2: Identify the Rate Determining Step
In the haloform reaction, the rate-determining step is the formation of the enolate ion from the ketone. This step is crucial because it determines how quickly the reaction proceeds.

### Step 3: Analyze the Role of Halogens
The rate of the haloform reaction does not depend on the concentration of halogens (X₂). This means that whether we use chlorine (Cl₂), bromine (Br₂), or iodine (I₂), the rate of enolate formation remains the same.

### Step 4: Compare the Reactivity of Halogens
While the rate of the reaction is independent of halogen concentration, the reactivity of the halogens does play a role in the overall reaction. Iodine is generally more reactive in the haloform reaction compared to chlorine and bromine due to the stability of the iodoform product (CHI₃) and the lower bond dissociation energy of the I-I bond.

### Step 5: Conclusion
Given that the rate-determining step is the formation of the enolate ion and that the reactivity of the halogens does not affect this step, the fastest reaction will be with the halogen that forms the most stable haloform product. In this case, the reaction is fastest with iodine (I₂) because it forms iodoform (CHI₃), which is a stable product.

### Final Answer
The rate of the haloform reaction is fastest with iodine (I₂).

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