Solved Naming Hydrocarbons Worksheet Name: Name the | Chegg.com - Free Printable

Let's go through each of the given hydrocarbon structures and name them according to IUPAC nomenclature. We’ll analyze the structure, identify the longest carbon chain, check for multiple bonds or branches, and assign the correct name.

---

1.

```
H H H
| | |
H - C - C - C - H
| | |
H H H
```

- This is a straight-chain alkane with 3 carbon atoms.
- All single bonds → alkane
- The prefix for 3 carbons is "prop", suffix "-ane"

✔ Name: Propane

---

2.

```
H H H H
| | | |
H - C = C - C - C - H
| | | |
H H H H
```

- Longest chain: 4 carbon atoms
- Double bond between C1 and C2
- Alkene → suffix "-ene"
- Numbering starts from the end nearest the double bond → double bond at C1-C2, so it’s but-1-ene

✔ Name: But-1-ene

---

3.

```
H
|
H - C ≡ C - C - H
| |
H H
```

- Longest chain: 3 carbon atoms
- Triple bond between C1 and C2
- Alkyne → suffix "-yne"
- Numbering from left to right: triple bond at C1-C2, so it’s prop-1-yne

✔ Name: Prop-1-yne

---

5.

```
H H H
| | |
H - C - C - C - H
| | |
H H - C - H
|
H
```

- Let’s draw this clearly:
- Main chain: 4 carbons (butane)
- A methyl group (-CH₃) attached to C2
- So: butane with a methyl on carbon 2

But wait — let’s number properly:

- If we number from left to right:
Carbon 1 – CH₃
Carbon 2 – CH(CH₃)
Carbon 3 – CH₂
Carbon 4 – CH₃

→ That gives 2-methylbutane

But wait — actually, the longest chain is 4 carbons, but there's a branch on C2.

Wait — let's count again:

The structure:
```
H H H
| | |
H - C - C - C - H
| | |
H H - C - H
|
H
```

So the bottom carbon (attached to C2) is a methyl group.

So main chain: 4 carbons → butane

Substituent: methyl group on carbon 2

✔ Name: 2-Methylbutane

But wait — is that correct? Let’s confirm:

- Chain: C1–C2–C3–C4
- At C2, there’s an extra CH₃
- So yes, 2-methylbutane

But note: 2-methylbutane is also known as isopentane

✔ Name: 2-Methylbutane

---

6.

```
H CH₃ H
| | |
H - C - C - C - H
| | |
H H H
```

- Longest chain: 3 carbons → propane
- Methyl group (-CH₃) on C2
- So: 2-methylpropane

Note: This is also called isobutane

✔ Name: 2-Methylpropane

---

7.

```
H H H H H
| | | | |
H - C - C = C - C - C - H
| | | | |
H H H H H
```

- Longest chain: 5 carbon atoms
- Double bond between C2 and C3
- Alkene → suffix "-ene"
- Numbering: Start from left → double bond at C2-C3 → pent-2-ene

✔ Name: Pent-2-ene

---

✔ Final Answers:

| Number | Structure | IUPAC Name |
|--------|-----------|------------|
| 1 |  | Propane |
| 2 |  | But-1-ene |
| 3 |  | Prop-1-yne |
| 5 |  | 2-Methylbutane |
| 6 |  | 2-Methylpropane |
| 7 |  | Pent-2-ene |

---

🔍 Summary of Rules Used:

1. Find the longest continuous carbon chain.
2. Identify functional groups (double/triple bonds).
3. Number the chain to give the lowest numbers to substituents or multiple bonds.
4. Name substituents (e.g., methyl, ethyl) and add them as prefixes.
5. Use suffixes:
- -ane for alkanes
- -ene for alkenes
- -yne for alkynes

Let me know if you'd like diagrams or further explanation!