Worksheet showing various alkyne structures for naming practice.

To solve the problem of naming the alkynes in the provided worksheet, we need to follow the IUPAC nomenclature rules for alkynes. Here's a step-by-step explanation of how to name each compound:

General Rules for Naming Alkynes:

1. Identify the longest carbon chain that contains the triple bond (C≡C).
2. Number the carbon chain starting from the end closest to the triple bond.
3. Name the parent chain based on the number of carbons in the longest chain containing the triple bond. The suffix for alkynes is "-yne".
4. Locate and name any substituents (e.g., methyl groups, ethyl groups) and indicate their positions using numbers.
5. Indicate the position of the triple bond by giving the lower possible number to the first carbon of the triple bond.

Step-by-Step Solution for Each Compound:

#### 1. First Compound:
```
HC≡C-CH(CH₃)-CH₃
```
- Longest chain: 4 carbons (butane).
- Triple bond: Located between C-1 and C-2.
- Substituent: Methyl group (CH₃) at C-2.
- Name: 2-Methylbut-1-yne.

#### 2. Second Compound:
```
CH₃-CH(CH₃)-C≡C-CH₃
```
- Longest chain: 5 carbons (pentane).
- Triple bond: Located between C-3 and C-4.
- Substituent: Methyl group (CH₃) at C-2.
- Name: 2-Methylpent-3-yne.

#### 3. Third Compound:
```
CH₃-CH(CH₃)-C≡C-CH(CH₃)-CH₃
```
- Longest chain: 6 carbons (hexane).
- Triple bond: Located between C-3 and C-4.
- Substituents: Two methyl groups (CH₃) at C-2 and C-5.
- Name: 2,5-Dimethylhex-3-yne.

#### 4. Fourth Compound:
```
CH₃-CH₂-C≡C-CH(CH₃)-CH₂-CH₃
```
- Longest chain: 7 carbons (heptane).
- Triple bond: Located between C-3 and C-4.
- Substituents: Methyl group (CH₃) at C-5 and ethyl group (CH₂CH₃) at C-7.
- Name: 5-Methyl-7-ethylhept-3-yne.

#### 5. Fifth Compound:
```
CH₃-O-CH(CH₃)-CH₂-C≡CH
```
- Longest chain: 5 carbons (pentane).
- Triple bond: Located between C-4 and C-5.
- Substituents: Methyl group (CH₃) at C-3 and methoxy group (OCH₃) at C-2.
- Name: 2-Methoxy-3-methylpent-4-yne.

#### 6. Sixth Compound:
```
CH₃-CH₂-C≡C-C(CH₃)₂-CH₃
```
- Longest chain: 6 carbons (hexane).
- Triple bond: Located between C-3 and C-4.
- Substituents: Two methyl groups (CH₃) at C-5.
- Name: 5,5-Dimethylhex-3-yne.

#### 7. Seventh Compound:
```
CH₃-CH₂-CH(CH₃)-CH₃
| |
C≡C CH₃
```
- Longest chain: 5 carbons (pentane).
- Triple bond: Located between C-2 and C-3.
- Substituents: Methyl group (CH₃) at C-4 and two methyl groups (CH₃) at C-3.
- Name: 3,3,4-Trimethylpent-2-yne.

#### 8. Eighth Compound:
```
CH₃-CH₂-CH₂-CH(CH₃)-CH₂-C≡C-CH₂-CH₃
```
- Longest chain: 9 carbons (nonane).
- Triple bond: Located between C-6 and C-7.
- Substituent: Methyl group (CH₃) at C-4.
- Name: 4-Methylnon-6-yne.

Final Answer:

\[
\boxed{
\begin{array}{l}
1. \text{2-Methylbut-1-yne} \\
2. \text{2-Methylpent-3-yne} \\
3. \text{2,5-Dimethylhex-3-yne} \\
4. \text{5-Methyl-7-ethylhept-3-yne} \\
5. \text{2-Methoxy-3-methylpent-4-yne} \\
6. \text{5,5-Dimethylhex-3-yne} \\
7. \text{3,3,4-Trimethylpent-2-yne} \\
8. \text{4-Methylnon-6-yne}
\end{array}
}
\]