Identify (X), (Y) andc (Z) in the given reaction :
`CH_(3)CHO overset(K_(2)Cr_(2)O_(7))underset(H_(2)SO_(4))to(X) overset(PCl_(5))to(Y)overset(C_(6)H_(6))underset(anh.AlCl_(3))to(Z)`

Options

A. `(X)=HCOOH, (Y)=COCl_(2),(Y)=COCl_(2), (Z)=C_(6)H_(5)Cl`
B. `(X)=CH_(3)COOH, (Y)=CH_(3)COCl, (Z)=C_(6)H_(5)COCH_(3)`
C. `(X)=CH_(3)COOH, (Y)=CH_(3)CH_(2)CH_(2)Cl, (Z)=C_(6)H_(5)CH_(2)CH_(2)CH_(3)`
D. `(X)=CH_(3)COCH_(3), (Y)=CH_(3)CHClCH_(3), (Z)=C_(6)H_(5)COCH_(3)`

Answer

To identify (X), (Y), and (Z) in the given reaction sequence, we will analyze each step of the reaction carefully.

### Step 1: Identify (X)
The starting compound is acetaldehyde (CH₃CHO). When acetaldehyde is treated with potassium dichromate (K₂Cr₂O₇) in the presence of sulfuric acid (H₂SO₄), it undergoes oxidation.

- **Reaction:**
\[ CH₃CHO + [O] \rightarrow CH₃COOH \]
- **Product (X):** Acetic acid (CH₃COOH)

### Step 2: Identify (Y)
Next, acetic acid (X) reacts with phosphorus pentachloride (PCl₅). This reaction typically converts carboxylic acids into acyl chlorides.

- **Reaction:**
\[ CH₃COOH + PCl₅ \rightarrow CH₃COCl + POCl₃ + HCl \]
- **Product (Y):** Acetyl chloride (CH₃COCl)

### Step 3: Identify (Z)
Now, acetyl chloride (Y) reacts with benzene (C₆H₆) in the presence of anhydrous aluminum chloride (AlCl₃), which is a Lewis acid catalyst. This reaction is known as the Friedel-Crafts acylation, where an acyl group is introduced into the benzene ring.

- **Reaction:**
\[ CH₃COCl + C₆H₆ \xrightarrow{AlCl₃} C₆H₅COCH₃ + HCl \]
- **Product (Z):** Acetophenone (C₆H₅COCH₃)

### Summary of Products
- (X) = Acetic acid (CH₃COOH)
- (Y) = Acetyl chloride (CH₃COCl)
- (Z) = Acetophenone (C₆H₅COCH₃)

### Final Answer
- (X) = Acetic acid
- (Y) = Acetyl chloride
- (Z) = Acetophenone