When an alkylhalide is dissolved in ethanol the following reaction beings to occur .
`R - X + EtOH `
`overset(S_N2"mechanism")rarrR-O-Et+HCI `
The overall order of reaction is .

Options

A. One
B. Two
C. Three
D. Four

Answer

To determine the overall order of the reaction when an alkyl halide (R-X) reacts with ethanol (EtOH) via an SN2 mechanism, we can follow these steps:

### Step 1: Understanding the Reaction
The reaction given is:
\[ R - X + \text{EtOH} \rightarrow R - O - \text{Et} + \text{HCl} \]
This indicates that an alkyl halide (R-X) is reacting with ethanol (EtOH) to form an ether (R-O-Et) and hydrochloric acid (HCl).

### Step 2: Identifying the Mechanism
The problem states that the reaction follows an SN2 mechanism. In an SN2 reaction, the nucleophile attacks the substrate in a single concerted step, leading to the formation of a transition state.

### Step 3: Determining the Rate Law
In an SN2 reaction, the rate of the reaction depends on the concentration of both the substrate (alkyl halide, R-X) and the nucleophile (ethanol, EtOH). Therefore, the rate law can be expressed as:
\[ \text{Rate} = k [R-X][EtOH] \]

### Step 4: Calculating the Overall Order of Reaction
The overall order of a reaction is determined by the sum of the powers of the concentration terms in the rate law. In this case:
- The order with respect to R-X is 1 (since it is raised to the power of 1).
- The order with respect to EtOH is also 1.

Thus, the overall order of the reaction is:
\[ 1 + 1 = 2 \]

### Conclusion
The overall order of the reaction when an alkyl halide reacts with ethanol via an SN2 mechanism is **2**.

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