The reaction of (S) - 2 - bromobutane with `OH^-` to produce (R) - butan -2 - ol will be

Options

A. first order in 2 - bromobutane only
B. first order in `OH^-` only
C. first order in 2 - bromobutane and first order in `OH^-`
D. second order in `OH^-`

Answer

To solve the problem, we need to analyze the reaction of (S)-2-bromobutane with hydroxide ions (OH^-) to produce (R)-butan-2-ol. Here’s the step-by-step solution:

### Step 1: Identify the Reaction Type
The reaction involves the conversion of (S)-2-bromobutane to (R)-butan-2-ol. Since the stereochemistry changes from S to R, this indicates that there is an inversion of configuration occurring during the reaction.

**Hint:** Look for changes in stereochemistry to determine the type of reaction mechanism.

### Step 2: Determine the Mechanism
The inversion of configuration suggests that the reaction follows an SN2 (Substitution Nucleophilic Bimolecular) mechanism. In an SN2 reaction, the nucleophile (OH^-) attacks the electrophilic carbon (the carbon attached to the bromine) from the opposite side of the leaving group (Br), resulting in inversion of configuration.

**Hint:** Recall that SN2 reactions involve a backside attack leading to inversion of configuration.

### Step 3: Write the Rate Law
In an SN2 reaction, the rate of the reaction is dependent on both the substrate (2-bromobutane) and the nucleophile (OH^-). Therefore, the rate law can be expressed as:

\[ \text{Rate} = k[\text{2-bromobutane}][\text{OH}^-] \]

This indicates that the reaction is first order with respect to both the substrate and the nucleophile.

**Hint:** Remember that the rate law for an SN2 reaction involves both the substrate and the nucleophile.

### Step 4: Conclusion
Based on the analysis, we conclude that the reaction of (S)-2-bromobutane with OH^- to produce (R)-butan-2-ol proceeds via an SN2 mechanism, and the rate law is first order in both the substrate and the hydroxide ion.

**Final Answer:** The reaction is an SN2 mechanism.

### Summary of Steps:
1. Identify the reaction type (inversion of configuration).
2. Determine the mechanism (SN2).
3. Write the rate law (first order in both substrate and nucleophile).
4. Conclude the nature of the reaction.