`"Propionic acid"overset(PCl_(5))toXoverset(C_(6)H_(6))underset(AlCl_(3))toY`.
In the above sequence Y is

Options

A. Phenylethylketone
B. Phenylacetate
C. Ethyl benzene
D. Ethyl benzoate

Answer

To solve the problem, we will follow the steps of the reaction sequence given in the question.

### Step 1: Identify the structure of Propionic Acid
Propionic acid has the molecular formula C3H6O2. Its structure can be represented as:
\[ \text{CH}_3\text{CH}_2\text{COOH} \]
This is a carboxylic acid with three carbon atoms.

### Step 2: Reaction of Propionic Acid with PCl5
When propionic acid reacts with phosphorus pentachloride (PCl5), it undergoes a substitution reaction where the hydroxyl (-OH) group of the carboxylic acid is replaced by a chlorine atom, forming an acyl chloride. The reaction can be represented as:
\[ \text{CH}_3\text{CH}_2\text{COOH} + \text{PCl}_5 \rightarrow \text{CH}_3\text{CH}_2\text{COCl} + \text{POCl}_3 + \text{HCl} \]
The product of this reaction, which we will denote as X, is propionyl chloride:
\[ X = \text{CH}_3\text{CH}_2\text{COCl} \]

### Step 3: Reaction of X (Propionyl Chloride) with Benzene in the presence of AlCl3
Next, we react the acyl chloride (X) with benzene (C6H6) in the presence of aluminum chloride (AlCl3), which acts as a Lewis acid. This reaction is an electrophilic aromatic substitution. The acyl chloride generates an acylium ion (carbocation) which can be represented as:
\[ \text{CH}_3\text{CH}_2\text{CO}^+ \]
The benzene ring, being electron-rich, attacks this electrophile, leading to the formation of a ketone. The reaction can be represented as:
\[ \text{C}_6\text{H}_6 + \text{CH}_3\text{CH}_2\text{CO}^+ \rightarrow \text{C}_6\text{H}_5\text{COCH}_2\text{CH}_3 \]
The product Y formed from this reaction is phenyl ethyl ketone, which can also be written as:
\[ Y = \text{C}_6\text{H}_5\text{COCH}_2\text{CH}_3 \]

### Conclusion
Thus, the final product Y is phenyl ethyl ketone.

### Final Answer
Y is phenyl ethyl ketone.

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