The number of secondary hydrogens in 2 , 2- dimethylbutane is :

Options

A. 8
B. 6
C. 4
D. 2

Explanation

To determine the number of secondary hydrogens in 2,2-dimethylbutane, we can follow these steps:

### Step 1: Understand the Structure of 2,2-Dimethylbutane
2,2-Dimethylbutane is a branched alkane. The base structure is butane, which consists of a straight chain of four carbon atoms. The "2,2-dimethyl" indicates that there are two methyl (CH₃) groups attached to the second carbon of the butane chain.

### Step 2: Draw the Structure
1. Start with the butane backbone:
```
C1 - C2 - C3 - C4
```
2. Add the methyl groups to the second carbon:
```
CH3
|
CH3 - C2 - C3 - C4
|
CH3
```

### Step 3: Identify the Types of Carbons
- **Primary Carbons**: Carbons attached to only one other carbon.
- **Secondary Carbons**: Carbons attached to two other carbons.
- **Tertiary Carbons**: Carbons attached to three other carbons.
- **Quaternary Carbons**: Carbons attached to four other carbons.

### Step 4: Analyze Each Carbon
1. **C1**: Attached to one carbon (C2) → Primary
2. **C2**: Attached to three carbons (C1, C3, and two CH₃ groups) → Tertiary
3. **C3**: Attached to two carbons (C2 and C4) → Secondary
4. **C4**: Attached to one carbon (C3) → Primary

### Step 5: Count the Secondary Hydrogens
Secondary hydrogens are the hydrogens attached to secondary carbons. In this structure:
- **C3** is the only secondary carbon and has two hydrogens (since it is connected to two other carbons).

### Conclusion
The number of secondary hydrogens in 2,2-dimethylbutane is **2**.

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