Question

IUPAC name of
\( \text{CH}_3 - \text{CH}(\text{OH}) - \text{CH}_2 - \text{CH}(\text{OH}) - \text{CH}(\text{C}_2\text{H}_5) \)
\( | \)
\( \text{CH}_3 - \text{CH}_2 \)

Hint:

Always be careful with terminal \( \text{C}_2\text{H}_5 \) or \( \text{C}_3\text{H}_7 \) groups in condensed structures. They often hide the true longest chain. Expanding them explicitly helps avoid selecting a shorter parent chain.

Answer 1

Step 1: Understanding the Concept:
To name the organic compound properly, we must determine the longest continuous carbon chain containing the principal functional groups (hydroxyl groups, \( -\text{OH} \)) and assign the lowest possible numbers to these groups.
Step 2: Key Formula or Approach:
The approach involves expanding the condensed formula, tracing the longest chain containing both \( -\text{OH} \) groups, numbering it to give the \( -\text{OH} \) groups the lowest locants, and naming the substituents alphabetically.
Step 3: Detailed Explanation:
Let's analyze the structure given:
It is a continuous chain from the left: \( \text{CH}_3 - \text{CH}(\text{OH}) - \text{CH}_2 - \text{CH}(\text{OH}) - \text{CH} \) ...
Attached to this last \( \text{CH} \) carbon is a \( (\text{C}_2\text{H}_5) \) group.
The vertical line \( | \) pointing down to \( \text{CH}_3 - \text{CH}_2 \) indicates that there is another ethyl group attached to the same \( \text{CH} \) carbon.
Starting from the left (methyl end), we trace through the carbons:
C-1: \( \text{CH}_3 \)
C-2: \( \text{CH}(\text{OH}) \)
C-3: \( \text{CH}_2 \)
C-4: \( \text{CH}(\text{OH}) \)
C-5: \( \text{CH} \)
From C-5, we have two identical ethyl groups (\( -\text{CH}_2\text{CH}_3 \)). One of these groups will form part of the main parent chain, making it C-6 and C-7.
The parent chain is therefore 7 carbons long (Heptane).
The remaining ethyl group on C-5 acts as a substituent.
Now, let's establish the numbering direction.
Numbering from left to right gives the principal functional groups (the two \( -\text{OH} \) groups) positions 2 and 4.
Numbering from right to left would give the \( -\text{OH} \) groups positions 4 and 6.
The lowest locant set is (2,4), so we number from left to right.
Substituent: An "ethyl" group at position 5.
Principal functional groups: Two hydroxyl groups "diol" at positions 2 and 4.
Combining these parts: 5-ethyl + heptane + 2,4-diol = 5-Ethylheptane-2,4-diol.
Step 4: Final Answer:
The IUPAC name is 5-Ethylheptane-2,4-diol.