The total number of secondary H-atoms in the structure given below are `(CH_(3))_(2)CHCH_(2)C_(2)H_(5)`

Options

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

Answer

To determine the total number of secondary hydrogen atoms in the given structure `(CH₃)₂CHCH₂C₂H₅`, we can follow these steps:

### Step 1: Draw the Expanded Structure
First, we need to draw the expanded structure of the compound. The given formula can be expanded as follows:

- `(CH₃)₂` indicates two methyl groups (CH₃).
- `CH` indicates a secondary carbon (attached to two other carbons).
- `CH₂` indicates a methylene group (attached to two other groups).
- `C₂H₅` indicates an ethyl group (CH₂CH₃).

Putting this together, the expanded structure looks like this:
```
CH₃
|
CH₃-C-CH₂-CH₂-CH₃
```

### Step 2: Identify the Carbon Atoms and Their Degrees
Next, we need to identify the degree of each carbon atom in the structure:
- The first two carbon atoms (from the two CH₃ groups) are primary (1°) because each is attached to only one carbon.
- The third carbon (the one connected to the two CH₃ groups) is secondary (2°) because it is attached to two other carbons.
- The fourth carbon (the CH₂ group) is also secondary (2°) because it is attached to two other carbons.
- The last carbon in the ethyl group is primary (1°) because it is attached to only one carbon.

### Step 3: Identify the Hydrogen Atoms
Now, we need to count the hydrogen atoms attached to each carbon:
- The two primary carbons (CH₃) each have 3 hydrogen atoms: 3 + 3 = 6 primary hydrogen atoms.
- The secondary carbon (attached to two CH₃ groups) has 1 hydrogen atom.
- The second secondary carbon (the CH₂ group) has 2 hydrogen atoms.
- The primary carbon in the ethyl group has 2 hydrogen atoms.

### Step 4: Count the Secondary Hydrogen Atoms
Now we can count the secondary hydrogen atoms:
- The secondary carbon (the one connected to the two CH₃ groups) contributes 1 secondary hydrogen atom.
- The other secondary carbon (the CH₂ group) contributes 2 secondary hydrogen atoms.

Thus, the total number of secondary hydrogen atoms is:
1 (from the first secondary carbon) + 2 (from the second secondary carbon) = **3 secondary hydrogen atoms**.

### Final Answer
The total number of secondary hydrogen atoms in the structure `(CH₃)₂CHCH₂C₂H₅` is **3**.

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