Alkanes Worksheet with molecular structures for naming practice.

To solve the problem of naming the given molecules, we need to follow the IUPAC (International Union of Pure and Applied Chemistry) nomenclature rules for alkanes. Here's a step-by-step explanation for each molecule:

---

General Rules for Naming Alkanes:

1. Identify the longest continuous carbon chain (this determines the base name).
2. Number the carbon atoms in the chain starting from the end that gives the lowest numbers to substituents.
3. Name the substituents (groups attached to the main chain) and indicate their positions using numbers.
4. Combine the names in alphabetical order for multiple substituents.

---

Solutions:

#### a)
```
CH₃—CH₂—CH—CH₃
|
CH₃
```
- The longest chain has 4 carbons → Butane.
- There is a methyl group (CH₃) on the second carbon.
- Name: 2-Methylbutane

#### b)
```
CH₃—CH—CH—CH₃
| |
CH₃ CH₃
```
- The longest chain has 4 carbons → Butane.
- There are two methyl groups (CH₃) on the second and third carbons.
- Name: 2,3-Dimethylbutane

#### c)
```
CH₃—CH—CH—CH₃
| |
CH₃ CH₂—CH₃
```
- The longest chain has 5 carbons → Pentane.
- There is a methyl group (CH₃) on the second carbon and an ethyl group (CH₂—CH₃) on the third carbon.
- Name: 2-Methyl-3-ethylpentane

#### d)
```
CH₃—CH₂—CH—CH₂—CH₃
|
CH₂—CH₂—CH₃
```
- The longest chain has 6 carbons → Hexane.
- There is a propyl group (CH₃—CH₂—CH₂—) on the fourth carbon.
- Name: 4-Propylhexane

#### e)
```
CH₃ CH₃ CH CH CH₂ CH₃
| | | | | |
CH₃ CH₃ CH₃ CH₃ CH₃ CH₃
```
- The longest chain has 6 carbons → Hexane.
- Every carbon in the chain has three methyl groups (CH₃).
- This is a highly branched structure where all carbons have maximum substitution.
- Name: 2,2,3,3,4,4,5,5-Octamethylhexane

#### f)
```
CH₃—CH₂—CH—CH₂—CH₂—CH₃
|
CH₃
```
- The longest chain has 6 carbons → Hexane.
- There is a methyl group (CH₃) on the fifth carbon.
- Name: 5-Methylhexane

#### g)
```
H₃C
|
H₃C—C—CH₃
|
H₃C
```
- The central carbon is bonded to four methyl groups (CH₃).
- This is a saturated hydrocarbon with a tetrahedral structure.
- Name: 2,2-Dimethylpropane (or Neopentane)

#### h)
```
H₂C—CH₃
|
H₃C—CH—CH₂—C—CH₃
|
CH₃
```
- The longest chain has 5 carbons → Pentane.
- There is an ethyl group (CH₃—CH₂—) on the second carbon and a methyl group (CH₃) on the third carbon.
- Name: 2-Ethyl-3-methylpentane

#### i)
```
CH₃
|
H₃C—C—CH₂—C—CH₂—CH₃
| |
CH₃ CH₃
```
- The longest chain has 6 carbons → Hexane.
- There are two methyl groups (CH₃) on the second and fifth carbons.
- Name: 2,5-Dimethylhexane

#### j)
```
H₂C—CH₃
|
H₃C—CH₂—C—CH₂—CH₂—C—CH₃
| |
CH₃ CH₃
```
- The longest chain has 7 carbons → Heptane.
- There is a methyl group (CH₃) on the third and sixth carbons.
- Name: 3,6-Dimethylheptane

---

Final Answers:

1. a) 2-Methylbutane
2. b) 2,3-Dimethylbutane
3. c) 2-Methyl-3-ethylpentane
4. d) 4-Propylhexane
5. e) 2,2,3,3,4,4,5,5-Octamethylhexane
6. f) 5-Methylhexane
7. g) 2,2-Dimethylpropane (or Neopentane)
8. h) 2-Ethyl-3-methylpentane
9. i) 2,5-Dimethylhexane
10. j) 3,6-Dimethylheptane

Boxed Final Answer:
\[
\boxed{
\begin{array}{ll}
\text{a)} & \text{2-Methylbutane} \\
\text{b)} & \text{2,3-Dimethylbutane} \\
\text{c)} & \text{2-Methyl-3-ethylpentane} \\
\text{d)} & \text{4-Propylhexane} \\
\text{e)} & \text{2,2,3,3,4,4,5,5-Octamethylhexane} \\
\text{f)} & \text{5-Methylhexane} \\
\text{g)} & \text{2,2-Dimethylpropane (or Neopentane)} \\
\text{h)} & \text{2-Ethyl-3-methylpentane} \\
\text{i)} & \text{2,5-Dimethylhexane} \\
\text{j)} & \text{3,6-Dimethylheptane} \\
\end{array}
}
\]