In the given reaction
`overset(Br)overset(|)(CH_2)-(CH_2)_(3)-CH_2OH underset("Toluene" 140^@C)overset(NaOH)(rarr)(X)`
'X' will be

Options

A. `overset(OH)overset(|)(CH_2)-(CH_2)_(4)-CH_2OH`
B. `CH_2=CH-(CH_2)_(3)-CH_2OH`
C. `CH_3-overset(OH)overset(|)(CH)-(CH_2)_(3)-CH_2OH`
D.

Answer

To solve the given reaction, we need to analyze the reactants and the conditions provided:

1. **Identify the Reactants**:
The reactant is 1-bromobutane (CH2Br-CH2-CH2-CH2OH) in the presence of NaOH and toluene at 140°C.

2. **Understanding the Role of NaOH**:
NaOH is a strong base, which can participate in acid-base reactions. In this case, it will deprotonate the alcohol (OH group) to form an alkoxide ion (O-).

3. **Deprotonation**:
The hydroxyl group (OH) will lose a proton (H+) due to the strong basicity of NaOH, resulting in the formation of the alkoxide ion:
\[ CH2Br-CH2-CH2-CH2OH \xrightarrow{NaOH} CH2Br-CH2-CH2-CH2O^{-} \]

4. **Nucleophilic Substitution**:
The alkoxide ion (O-) is a strong nucleophile and will attack the carbon atom bonded to bromine (Br) in a nucleophilic substitution reaction (S_N2 mechanism). This will result in the substitution of bromine with the alkoxide ion:
\[ CH2Br-CH2-CH2-CH2O^{-} \rightarrow CH2O-CH2-CH2-CH2O \]

5. **Formation of a Six-Membered Ring**:
The alkoxide ion can also lead to the formation of a cyclic ether (a six-membered ring) through an intramolecular reaction. The oxygen from the alkoxide ion attacks the carbon adjacent to the bromine, leading to the formation of a six-membered cyclic ether:
\[ \text{Cyclic Ether: } \text{(C6H12O)} \]

6. **Final Product**:
The final product 'X' formed from this reaction is a six-membered cyclic ether, specifically 1,4-dioxane.

Thus, the answer for 'X' is **1,4-dioxane**.