Among the following four structures I to IV
(I) `H_(5)C_(2)-overset(CH_(3))overset(|)(C)H-C_(3)H_(7)`
(II) `H_(3)C-overset(O)overset(|)(C)-overset(CH_(3))overset(|)(C)H-CH_(2)H_(5)`
(III) `H-underset(H)underset(|)overset(H)overset(|)(H^(+))`
(IV) `H_(5)C_(2)-overset(CH_(3))overset(|)(C)H-C_(2)H_(5)`
In is true that

Options

A. only II and IV are chiral compounds
B. all four are chiral compounds
C. only I and II are chiral compounds
D. only IIII is a chiral compound

Answer

To determine which of the given structures are chiral, we need to identify the presence of chiral centers in each structure. A chiral center is typically a carbon atom that is bonded to four different groups. Let's analyze each structure step by step.

### Step 1: Analyze Structure I
**Structure I:** `H_(5)C_(2)-overset(CH_(3))overset(|)(C)H-C_(3)H_(7)`

1. Identify the carbon atoms and their substituents.
2. The central carbon (C) is bonded to:
- Ethyl group (C2H5)
- Methyl group (CH3)
- Propyl group (C3H7)
- Hydrogen (H)

3. Since all four groups attached to this carbon are different, this carbon is a chiral center.

**Conclusion for Structure I:** Chiral.

### Step 2: Analyze Structure II
**Structure II:** `H_(3)C-overset(O)overset(|)(C)-overset(CH_(3))overset(|)(C)H-CH_(2)H_(5)`

1. Identify the central carbon atoms.
2. The carbon attached to the carbonyl (C=O) is bonded to:
- Methyl group (CH3)
- Ethyl group (C2H5)
- Hydrogen (H)
- Carbonyl group (C=O)

3. All four groups are different, making this carbon a chiral center.

**Conclusion for Structure II:** Chiral.

### Step 3: Analyze Structure III
**Structure III:** `H-underset(H)underset(|)overset(H)overset(|)(H^(+))`

1. This structure has a carbon atom bonded to:
- Three hydrogen atoms (H)
- One positive charge (H+)

2. Since there are three identical hydrogen atoms, this carbon does not have four different groups.

**Conclusion for Structure III:** Not chiral.

### Step 4: Analyze Structure IV
**Structure IV:** `H_(5)C_(2)-overset(CH_(3))overset(|)(C)H-C_(2)H_(5)`

1. The central carbon is bonded to:
- Ethyl group (C2H5)
- Methyl group (CH3)
- Ethyl group (C2H5)
- Hydrogen (H)

2. Since there are two identical ethyl groups, this carbon does not have four different groups.

**Conclusion for Structure IV:** Not chiral.

### Final Conclusion
From the analysis:
- Structure I is chiral.
- Structure II is chiral.
- Structure III is not chiral.
- Structure IV is not chiral.

Thus, the correct answer is that only structures I and II are chiral.