18 C-H and 7 C- C sigma bond are in

Options

A. cyclohexane
B. 3,3-dimethylpentane
C. 2,2,3-trimethylpentane
D. n-heptane

Answer

To determine which compound contains 18 C-H bonds and 7 C-C sigma bonds, we will analyze the structures of the given compounds step by step.

### Step 1: Understand the Requirements
We need to find a compound that has:
- 18 C-H bonds
- 7 C-C sigma bonds

### Step 2: Analyze Cyclohexane
1. **Structure of Cyclohexane**: Cyclohexane has a ring structure with 6 carbon atoms.
2. **C-H Bonds**: Each carbon in cyclohexane is bonded to 2 hydrogen atoms. Therefore, the total number of C-H bonds is:
\[ \text{C-H bonds} = 6 \text{ (carbons)} \times 2 \text{ (hydrogens per carbon)} = 12 \]
3. **C-C Bonds**: Cyclohexane has 6 C-C bonds (one between each pair of adjacent carbons).
4. **Conclusion**: Cyclohexane has 12 C-H bonds and 6 C-C bonds, so it does not satisfy the requirements.

### Step 3: Analyze 3,3-Dimethylpentane
1. **Structure of 3,3-Dimethylpentane**: It has a backbone of 5 carbon atoms with 2 methyl groups on the third carbon.
2. **C-C Bonds**: The total number of C-C bonds can be counted as follows:
- There are 5 main carbon atoms plus 2 from the methyl groups, leading to a total of 7 C-C bonds.
3. **C-H Bonds**: Count the hydrogen atoms:
- Each of the 5 main carbons contributes a certain number of hydrogens depending on their bonding.
- After counting, we find that it has fewer than 18 C-H bonds.
4. **Conclusion**: 3,3-Dimethylpentane does not satisfy the requirement.

### Step 4: Analyze 2,2,3-Trimethylpentane
1. **Structure of 2,2,3-Trimethylpentane**: It has a backbone of 5 carbon atoms with 3 methyl groups attached.
2. **C-C Bonds**: Counting the C-C bonds gives us:
- 7 C-C bonds.
3. **C-H Bonds**: Counting the hydrogen atoms, we find:
- 18 C-H bonds.
4. **Conclusion**: 2,2,3-Trimethylpentane satisfies both requirements.

### Step 5: Analyze n-Heptane
1. **Structure of n-Heptane**: It has a straight chain of 7 carbon atoms.
2. **C-C Bonds**: Counting the C-C bonds gives us:
- 6 C-C bonds.
3. **C-H Bonds**: Counting the hydrogen atoms gives us:
- Fewer than 18 C-H bonds.
4. **Conclusion**: n-Heptane does not satisfy the requirement.

### Final Conclusion
The compound that contains 18 C-H bonds and 7 C-C sigma bonds is **2,2,3-Trimethylpentane**.

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