Condiser the reactions,
(i) `(CH_(3))_(2)CH-CH_(2)Broverset(C_(2)H_(5)OH)rarr(CH_(3))_(2)CH-CH_(2)OC_(2)H_(5)+HBr`
(ii) `(CH_(3))_(2)CH-CH_(2)Broverset(C_(2)H_(5)O^(-))rarr(CH_(3))_(2)CH-CH_(2)OC_(2)H_(5)+Br^(-)`
The mechanism of reactions (i) and (ii) are respectively :

Options

A. `S_(N))2 and S_(N)`2
B. `S_(N)2 and S_(N)`1
C. `S_(N)1 and S_(N)2`
D. `S_(N) 1 and S_(N)1 `

Answer

To determine the mechanisms of the given reactions, we will analyze each reaction step by step.

### Step 1: Analyze Reaction (i)
The first reaction is:
\[ (CH_3)_2CH-CH_2Br \overset{C_2H_5OH}{\rightarrow} (CH_3)_2CH-CH_2OC_2H_5 + HBr \]

1. **Identify the Reactant**: The reactant is a haloalkane, specifically a primary alkyl halide since the carbon attached to the bromine is connected to only one other carbon.

2. **Mechanism Type**: The reaction involves the substitution of the bromine atom with an ethoxy group (from ethanol). Since the alkyl halide is primary, it is less sterically hindered, making it more favorable for an SN2 mechanism.

3. **SN2 Mechanism**: In the SN2 mechanism, the nucleophile (ethanol in this case) attacks the carbon atom from the opposite side of the leaving group (Br), resulting in a simultaneous bond formation and bond breaking. This leads to an inversion of configuration at the carbon center.

### Step 2: Analyze Reaction (ii)
The second reaction is:
\[ (CH_3)_2CH-CH_2Br \overset{C_2H_5O^-}{\rightarrow} (CH_3)_2CH-CH_2OC_2H_5 + Br^- \]

1. **Identify the Reactant**: Similar to the first reaction, the reactant is again a primary alkyl halide.

2. **Mechanism Type**: Here, the nucleophile is the ethoxide ion (C2H5O^-), which is a strong nucleophile. The reaction also involves substitution of the bromine atom with the ethoxy group.

3. **SN2 Mechanism**: Since the ethoxide ion is a strong nucleophile and the alkyl halide is primary, this reaction also proceeds via the SN2 mechanism. The nucleophile attacks the carbon atom from the opposite side of the bromine, leading to the formation of the ether and the release of bromide ion.

### Conclusion
Both reactions proceed via the SN2 mechanism due to the nature of the alkyl halide (primary) and the strong nucleophiles involved.

### Final Answer
The mechanisms of reactions (i) and (ii) are respectively:
**SN2 and SN2**.