In `S_(N)1` reaction of `(S)-2` bromobutane with water, two substitution products are formed one has the same relative configuration as the reactant and the other has the inverted configuration. This is in most `S_(N)1` reactions, the racemic product is non-50:50 mixture i.e, racemization takes place the inverted product is more than 50% . the formation of different composition of the product is due to following steps involved in `S_(N)` reactions.
`R-X " " to R^(+) X^(-) to R^(+) " " "solvent" X^(-) " " to R^(+)+X^(-)`
`{:("Undissociated Molecule", "Intimate ion pair", "solvent-separated ion pair", "dissociated ions"),(I,II,III,IV):}`
Which type of intermediate is formed in the reaction of (S)-2 bromobutane with water ?

Options

A. `sp^(3)` hybridized
B. `sp^(2)` hybridized
C. sp hybridized
D. A transition state

Answer

To solve the question regarding the type of intermediate formed in the reaction of (S)-2-bromobutane with water in an SN1 reaction, we can follow these steps:

### Step 1: Understand the Reaction Mechanism
In an SN1 reaction, the mechanism involves two main steps: the formation of a carbocation intermediate and then the nucleophile attacks the carbocation. The first step is the rate-determining step where the leaving group (in this case, bromide) departs, forming a carbocation.

**Hint:** Remember that SN1 reactions are characterized by the formation of a carbocation intermediate after the leaving group departs.

### Step 2: Identify the Starting Material
The starting material is (S)-2-bromobutane. This compound has a bromine atom (the leaving group) attached to the second carbon of the butane chain.

**Hint:** Identify the stereochemistry of the starting material, as it will help in understanding the product configurations.

### Step 3: Formation of the Carbocation
When (S)-2-bromobutane undergoes an SN1 reaction, the bromine atom leaves, resulting in the formation of a carbocation. For 2-bromobutane, this carbocation will be a secondary carbocation, which is generally stable.

**Hint:** Secondary carbocations are formed in SN1 reactions, and they are sp² hybridized due to the planar structure of the carbocation.

### Step 4: Nucleophilic Attack
After the formation of the carbocation, water (the nucleophile) can attack the positively charged carbon. Since the carbocation is planar, the nucleophile can attack from either side, leading to the formation of two different products: one with the same configuration as the reactant and one with inverted configuration.

**Hint:** The planar nature of the carbocation allows for attack from both sides, leading to racemization.

### Step 5: Conclusion on the Type of Intermediate
The intermediate formed during the reaction of (S)-2-bromobutane with water is a carbocation, specifically an sp² hybridized carbocation. This is because the carbon atom in the carbocation has three substituents and is trigonal planar.

**Final Answer:** The type of intermediate formed in the reaction of (S)-2-bromobutane with water is an sp² hybridized carbocation.