Complete catalytic hydrogenation of napthalene gives decalin `(C_(10)H_(18))`. The number of isomers of decalin formed and the total number of isomers of decalin possible are respectively.

Options

A. 1,2
B. 2,2
C. 2,4
D. 3,4

Answer

To solve the problem regarding the catalytic hydrogenation of naphthalene to form decalin, we will break it down into steps to find the number of isomers formed and the total number of isomers possible.

### Step 1: Understanding the Reaction
Naphthalene (C₁₀H₈) undergoes complete catalytic hydrogenation to form decalin (C₁₀H₁₈). The process involves the addition of hydrogen (H₂) across the double bonds of naphthalene.

### Step 2: Identifying the Structure of Decalin
Decalin can exist in two structural forms:
1. **Cis-decalin**: In this form, the two hydrogen atoms on the carbon atoms that are part of the bridge (the two carbons that are connected directly) are on the same side of the ring.
2. **Trans-decalin**: In this form, the hydrogen atoms on the bridge carbons are on opposite sides of the ring.

### Step 3: Determining the Number of Isomers Formed
When naphthalene is completely hydrogenated, it can yield both cis and trans forms of decalin. However, under certain conditions (like higher temperatures), the trans isomer is more thermodynamically stable and may be favored.

Thus, during the complete hydrogenation of naphthalene, we primarily obtain:
- **1 Isomer formed**: The trans-decalin is the major product when considering stability.

### Step 4: Total Number of Isomers of Decalin
The total number of isomers of decalin includes both the cis and trans forms. Therefore:
- **Total Number of Isomers Possible**: 2 (cis and trans).

### Final Answer
The number of isomers of decalin formed is **1**, and the total number of isomers of decalin possible is **2**.

### Summary
- Number of isomers formed: **1**
- Total number of isomers possible: **2**