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Question: In the following reaction, ether linkage is cleaved by \(PC{l_5}\) \(R - O - R' + PC{l_5} \to RCl...

In the following reaction, ether linkage is cleaved by PCl5PC{l_5}
R−O−R′+PCl5→RCl+R′Cl+POCl3R - O - R' + PC{l_5} \to RCl + R'Cl + POC{l_3}
If C5H12O{C_5}{H_{12}}O (ether) forms 2-chloropropane as one of the products, then ether
A) 1-ethoxypropane
B) 2-ethoxypropane
C) 1-methoxybutane
D) 2-methoxypropane

Explanation

Solution

Given the molecular formula of the ether in the question is C5H12O{C_5}{H_{12}}O and when this ether is cleaved byPCl5PC{l_5}, we get 2-chloropropane as one of the products. You must know the chemical formula of 2-chloropropane and it is CH3−CH(Cl)−CH3C{H_3} - CH(Cl) - C{H_3}. Do the chemical reaction of C5H12O{C_5}{H_{12}}O with PCl5PC{l_5} and examine the products.

Complete step by step solution:
In the question, it is given that ether linkage (R−O−R’R-O-R’) is cleaved by PCl5PC{l_5} as follows:
R−O−R′+PCl5→RCl+R′Cl+POCl3R - O - R' + PC{l_5} \to RCl + R'Cl + POC{l_3}
Now, the molecular formula of the given ether in the question is C5H12O{C_5}{H_{12}}O
When C5H12O{C_5}{H_{12}}O is cleaved by PCl5PC{l_5}, we get 2-chloropropane as one of the products.
As you know, the molecular formula of 2-chloropropane is: CH3−CH(Cl)−CH3C{H_3} - CH(Cl) - C{H_3}. Thus, it has three carbon atoms and seven hydrogen atoms. Consequently, we are left with C2H5{C_2}{H_5} unit from the ether C5H12O{C_5}{H_{12}}O, after getting 2-chloropropane as one of the products. Since ether group is R−O−R’R - O - R’, the required R for the given ether will be C2H5{C_2}{H_5} and R’{R’} will be the hydrocarbon unit from 2-chloropropane. Hence, the chemical name of the ether C5H12O{C_5}{H_{12}}O will be 2-ethoxypropane.
Now, we can write the required chemical equation between given ether, C5H12O{C_5}{H_{12}}O and PCl5PC{l_5} as follows:

Hence, C5H12O{C_5}{H_{12}}O (ether) is 2-ethoxypropane.

Thus, option B is the correct answer.

Note: Phosphorus pentachloride, PCl5PC{l_5} is used as a chlorinating agent. The reaction of cleavage of ethers refers to the chemical substitution reaction. Due to the higher stability of ethers, the cleavage of the C-O linkage is not done easily. Specific reagents are required for cleavage of ethers and PCl5PC{l_5} is that one reagent. It should also be noted from the given chemical reaction in question that dialkyl ethers on reacting with phosphorus pentachloride form alkyl chlorides.