`C_(5)H_(10)overset(H_(2)//Ni)rarr(X) overset(Cl_(2)//hv)rarr 3` monochloro structural isomers for compound `C_(5)H_(10)` how many pairs of geometrical isomers are possible

Options

A. 1
B. 2
C. 3
D. None

Answer

To solve the problem step by step, we will analyze the reactions and the isomers formed.

### Step 1: Identify the starting compound
The starting compound is \( C_5H_{10} \). This compound can be an alkene, as it has the general formula for alkenes (\( C_nH_{2n} \)).

### Step 2: Hydrogenation of \( C_5H_{10} \)
When \( C_5H_{10} \) undergoes hydrogenation in the presence of \( H_2 \) and nickel (Ni), it converts into an alkane, specifically \( C_5H_{12} \). This reaction adds hydrogen across the double bond of the alkene.

**Reaction:**
\[ C_5H_{10} + H_2 \xrightarrow{Ni} C_5H_{12} \]

### Step 3: Identify structural isomers of \( C_5H_{12} \)
The next step is to identify the structural isomers of \( C_5H_{12} \). The possible structural isomers for pentane (\( C_5H_{12} \)) include:
1. n-Pentane (straight chain)
2. Isopentane (2-methylbutane)
3. Neopentane (2,2-dimethylpropane)

### Step 4: Chlorination of \( C_5H_{12} \)
When \( C_5H_{12} \) is treated with chlorine (\( Cl_2 \)) in the presence of light (hv), it undergoes free radical substitution to form monochloro derivatives.

The three structural isomers of \( C_5H_{12} \) will lead to different monochloro products based on the positions of the chlorine atom.

### Step 5: Count the monochloro structural isomers
For each structural isomer of \( C_5H_{12} \):
- n-Pentane can yield 1 monochloro isomer.
- Isopentane can yield 3 different monochloro isomers due to the different positions of chlorine.
- Neopentane can yield 1 monochloro isomer.

Thus, the total number of monochloro structural isomers is:
1 (from n-pentane) + 3 (from isopentane) + 1 (from neopentane) = 5 monochloro structural isomers.

### Step 6: Determine pairs of geometrical isomers
Geometrical isomers are relevant for alkenes, not alkanes. However, if we consider the original alkene \( C_5H_{10} \) before hydrogenation, we can find geometrical isomers.

For example, consider the alkene:
- 2-Pentene can exist as cis and trans isomers.

Thus, for the alkene \( C_5H_{10} \):
- 2-Pentene has 1 pair of geometrical isomers (cis and trans).

### Conclusion
The total number of pairs of geometrical isomers possible for the compound \( C_5H_{10} \) is 1.

### Final Answer
**1 pair of geometrical isomers.**