In the following sequence of reactions:
`CH_(3)CH_(2)CH_(2)OHoverset(P+I_(2))rarrAoverset(Mg)underset("dry ether")rarrBoverset(HCHO)rarrCoverset(H_(2)O)rarrD` the compound `D` is:

Options

A. butanal
B. n-butyl alcohol
C. n-propyl alcohol
D. propanal

Answer

To solve the problem step by step, we will analyze each reaction in the sequence provided:

### Step 1: Identify the starting compound
The starting compound is **CH₃CH₂CH₂OH**, which is **1-butanol**.

### Step 2: Reaction with phosphorus and iodine
When 1-butanol reacts with phosphorus (P) and iodine (I₂), it undergoes a halogenation reaction to form **1-bromobutane** (or **1-iodobutane**). The reaction can be summarized as:
\[ \text{CH}_3\text{CH}_2\text{CH}_2\text{OH} + \text{P} + \text{I}_2 \rightarrow \text{CH}_3\text{CH}_2\text{CH}_2\text{I} \]
This compound is now referred to as **A**.

### Step 3: Formation of Grignard reagent
Next, the compound A (1-iodobutane) reacts with magnesium (Mg) in dry ether to form the Grignard reagent:
\[ \text{CH}_3\text{CH}_2\text{CH}_2\text{I} + \text{Mg} \rightarrow \text{CH}_3\text{CH}_2\text{CH}_2\text{MgI} \]
This compound is now referred to as **B**.

### Step 4: Reaction with formaldehyde
The Grignard reagent (B) then reacts with formaldehyde (HCHO). The reaction is as follows:
\[ \text{CH}_3\text{CH}_2\text{CH}_2\text{MgI} + \text{HCHO} \rightarrow \text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{OH} \]
This results in the formation of a new alcohol, which is now referred to as **C**.

### Step 5: Hydrolysis of the Grignard addition product
Finally, the addition product (C) is hydrolyzed with water (H₂O):
\[ \text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{MgI} + \text{H}_2\text{O} \rightarrow \text{CH}_3\text{CH}_2\text{CH}_2\text{CH}_2\text{OH} + \text{Mg(OH)I} \]
This gives us **n-butanol** (or **1-butanol**), which is now referred to as **D**.

### Conclusion
The final compound D is **n-butanol** (or **1-butanol**).

### Summary of Steps:
1. Start with 1-butanol (CH₃CH₂CH₂OH).
2. React with P and I₂ to form 1-iodobutane (A).
3. React A with Mg in dry ether to form the Grignard reagent (B).
4. React B with formaldehyde (HCHO) to form the addition product (C).
5. Hydrolyze C with water to form n-butanol (D).