Question

problem set | nomenclature and structuring
general instruction: write the appropriate iupac names and structures of the following problem set. write your answer beside the structure/name. make sure to underline the final answer.
alkanes
i.
a)
b)
c)
d)
e)
f)
g)
h)
i)

Answer:

To solve the IUPAC naming for these alkanes, we follow the IUPAC rules for alkanes: identify the parent chain (longest continuous carbon chain), number the chain to give substituents the lowest possible numbers, identify and name the substituents, and assemble the name. Let's solve each part:

Part (a)

Step 1: Identify the parent chain

The longest continuous carbon chain has 7 carbons (heptane).

Step 2: Identify substituents

There are two methyl groups (\( \text{CH}_3 \)): one at carbon 3, one at carbon 4.

Step 3: Assemble the name

Using IUPAC rules, the name is \( \boldsymbol{3,4\text{-dimethylheptane}} \).

Part (b)

Step 1: Identify the parent chain

The longest continuous carbon chain has 7 carbons (heptane), with a cyclopentyl group (cyclopentane ring) attached.

Step 2: Number the chain

The cyclopentyl group is at carbon 1 (since it’s the substituent, we number the main chain to give it the lowest number).

Step 3: Assemble the name

The name is \( \boldsymbol{1\text{-cyclopentylheptane}} \).

Part (c)

Step 1: Identify the parent chain

The longest continuous carbon chain has 9 carbons (nonane).

Step 2: Identify substituents

• Methyl groups (\( \text{CH}_3 \)) at carbons 3, 6, 7.
• Isopropyl group (\( \text{CH(CH}_3\text{)}_2 \)) at carbon 4.

Step 3: Assemble the name

Using alphabetical order for substituents (isopropyl comes before methyl), the name is \( \boldsymbol{4\text{-isopropyl-3,6,7-trimethylnonane}} \).

Part (d)

Step 1: Identify the parent chain

The longest continuous carbon chain has 9 carbons (nonane).

Step 2: Identify substituents

• Methyl groups (\( \text{CH}_3 \)) at carbons 2, 7.
• Ethyl groups (\( \text{C}_2\text{H}_5 \)) at carbons 3, 6.

Step 3: Assemble the name

Using alphabetical order (ethyl before methyl), the name is \( \boldsymbol{3,6\text{-diethyl-2,7-dimethylnonane}} \).

Part (e)

Step 1: Identify the parent chain

The longest continuous carbon chain has 8 carbons (octane).

Step 2: Identify substituents

• Methyl group (\( \text{CH}_3 \)) at carbon 5.
• Ethyl group (\( \text{C}_2\text{H}_5 \)) at carbon 3.
• Isopropyl group (\( \text{CH(CH}_3\text{)}_2 \)) at carbon 6? Wait, re-examining: Wait, the structure has a 3-ethyl, 5-methyl, and a substituent at 6? Wait, no—let’s re-express. Wait, the parent chain is octane. Let’s count again:

Wait, the structure: main chain is 8 carbons. Substituents: ethyl at 3, methyl at 5, and another? Wait, no—maybe I miscounted. Let’s re-express:

Wait, the correct parent chain for (e) is octane. Substituents: 3-ethyl, 5-methyl, and 6-isopropyl? No, let’s do it properly:

Longest chain: 8 carbons (octane). Numbering from the end closest to substituents. Substituents: ethyl at C3, methyl at C5, and isopropyl at C6? No, maybe:

Wait, the structure has:

• Ethyl (\( \text{C}_2\text{H}_5 \)) at C3.
• Methyl (\( \text{CH}_3 \)) at C5.
• Isopropyl (\( \text{CH(CH}_3\text{)}_2 \)) at C6? No, perhaps the correct name is \( \boldsymbol{3\text{-ethyl-5-methyl-6-isopropyloctane}} \)? Wait, no—let’s check again. Wait, maybe the parent chain is 9? No, let’s count the carbons in the main chain. Let’s draw the structure:

The main chain (longest) has 8 carbons. Substituents: ethyl (C2H5) at C3, methyl (CH3) at C5, and isopropyl (CH(CH3)2) at C6. So the name is \( \boldsymbol{3\text{-ethyl-5-methyl-6-isopropyloctane}} \).

Part (f)

Step 1: Identify the parent chain

The longest continuous carbon chain has 8 carbons (octane), with a cycloheptyl group (cycloheptane ring) attached.

Step 2: Identify substituents

• Methyl groups (\( \text{CH}_3 \)) at carbons 3, 4.
• Ethyl group (\( \text{C}_2\text{H}_5 \)) at carbon 5.

Step 3: Assemble the name

The cycloheptyl group is at carbon 1 of the main chain. So the name is \( \boldsymbol{1\text{-cycloheptyl-3,4-dimethyl-5-ethyloctane}} \).

Part (g)

Step 1: Identify the parent chain

The longest continuous carbon chain has 8 carbons (octane), with a cyclohexyl group (cyclohexane ring) attached.

Step 2: Identify substituents

• Methyl groups (\( \text{CH}_3 \)) at carbons 1 (on cyclohexane) and 2 (on cyclohexane).

Step 3: Assemble the name

The cyclohexyl group is part of the parent? Wait, no—wait, the structure has a cyclohexane ring with a butyl chain (4 carbons) and methyl groups. Wait, re-express:

Longest chain: 8 carbons (octane) with a cyclohexyl ring. Substituents: methyl at C1 (cyclohexane), methyl at C2 (cyclohexane). So the name is \( \boldsymbol{1,2\text{-dimethyl-4-cyclohexyloctane}} \)? Wait, no—let’s count the main chain. The main chain is 8 carbons (octane), with the cyclohexyl group attached at carbon 4. The cyclohexane ring has methyl groups at C1 and C2 (relative to the attachment). So the name is \( \boldsymbol{1,2\text{-dimethyl-4-cyclohexyloctane}} \).

Part (h)

Step 1: Identify the parent chain

The longest continuous carbon chain has 10 carbons (decane).

Step 2: Identify substituents

• Ethyl groups (\( \text{C}_2\text{H}_5 \)) at carbons 3, 6.
• Methyl groups (\( \text{CH}_3 \)) at carbons 4, 7.

Step 3: Assemble the name

Using alphabetical order (ethyl before methyl), the name is \( \boldsymbol{3,6\text{-diethyl-4,7-dimethyldecane}} \).

Part (i)

Step 1: Identify the parent chain

The longest continuous carbon chain has 8 carbons (octane), with a cyclohexyl group (cyclohexane ring) attached.

Step 2: Identify substituents

• Methyl group (\( \text{CH}_3 \)) at carbon 3 (on cyclohexane).

Step 3: Assemble the name

The cyclohexyl group is attached at carbon 3 of the main chain? Wait, no—wait, the structure: main chain is 5 carbons? No, wait, re-express:

Longest chain: 8 carbons (octane) with a cyclohexane ring. Wait, no—let’s count: the main chain (non-cyclic) has 5 carbons? No, I think I made a mistake. Wait, the structure for (i) is a cyclohexane ring with a propyl chain (3 carbons) and a methyl group. Wait, no—let’s do it properly:

Parent chain: cyclohexane (6 carbons) with a butyl chain (4 carbons) and a methyl group. Wait, no—longest chain: 8 carbons? No, let’s count the carbons:

• Cyclohexane ring (6 carbons) + 3 carbons (propyl) + 1 carbon (methyl)? No, I think the correct parent chain is octane with a cyclohexyl group. Wait, no—let’s look again:

The structure for (i) is: cyclohexane ring with a methyl group at C3, and a propyl chain (3 carbons) attached. Wait, no—main chain: 8 carbons? No, I think the correct name is \( \boldsymbol{3\text{-methyl-4-cyclohexyloctane}} \)? Wait, no—let’s count the main chain (longest continuous chain):

The longest chain is 8 carbons (octane), with the cyclohexyl group attached at carbon 4. The cyclohexane ring has a methyl group at carbon 3. So the name is \( \boldsymbol{3\text{-methyl-4-cyclohexyloctane}} \).

Final Answers (Underlined)

a) \( \underline{3,4\text{-dimethylheptane}} \)
b) \( \underline{1\text{-cyclopentylheptane}} \)
c) \( \underline{4\text{-isopropyl-3,6,7-trimethylnonane}} \)
d) \( \underline{3,6\text{-diethyl-2,7-dimethylnonane}} \)
e) \( \underline{3\text{-ethyl-5-methyl-6-isopropyloctane}} \) (Note: Verify chain length and numbering)
f) \( \underline{1\text{-cycloheptyl-3,4-dimethyl-5-ethyloctane}} \)
g) \( \underline{1,2\text{-dimethyl-4-cyclohexyloctane}} \)
h) \( \underline{3,6\text{-diethyl-4,7-dimethyldecane}} \)
i) \( \underline{3\text{-methyl-4-cyclohexyloctane}} \)

(Note: For precise naming, always verify chain length, numbering, and substituent positions. The above follows IUPAC rules for alkane nomenclature.)