Provide the correct IUPAC name for the following compound

Provide the correct IUPAC name for the following compound. Include stereochemistry if appropriate: Br

The Correct Answer and Explanation is:

The correct IUPAC name for the compound is:
(2S,4S)-2-bromo-3-ethyl-4-methylhexane

Explanation

To determine the correct IUPAC name for the given compound, we follow a systematic, step-by-step process:

1. Identify the Parent Carbon Chain:
The first step is to find the longest continuous chain of carbon atoms. By examining the structure, we can trace a chain of six carbon atoms. This chain starts from the methyl group on the far left, proceeds through the two chiral centers, and ends with the ethyl group on the right. Any other potential path results in a shorter chain. Therefore, the parent alkane is hexane.

2. Number the Parent Chain:
The chain must be numbered to give the substituents the lowest possible locants (positions). We have two options for numbering the six-carbon chain:

• Numbering from left to right: This places the substituents at positions 2 (bromo), 3 (ethyl), and 4 (methyl). The locant set is (2,3,4).
• Numbering from right to left: This places the substituents at positions 3 (methyl), 4 (ethyl), and 5 (bromo). The locant set is (3,4,5).

According to IUPAC rules, we compare the locant sets at the first point of difference. Since 2 is lower than 3, the correct numbering is from left to right. The base name is therefore 2-bromo-3-ethyl-4-methylhexane.

3. Determine the Stereochemistry (R/S Configuration):
The compound has two chiral centers at carbons C2 and C4. We must determine the absolute configuration (R or S) for each using the Cahn-Ingold-Prelog (CIP) priority rules.

• Configuration at C2:
  1. Assign priorities: The four groups on C2 are: -Br (bromo), -CH(ethyl)CH(methyl)CH2CH3 (the rest of the chain at C3), -CH3 (methyl), and an implied -H (hydrogen). Priorities are assigned based on atomic number:
     • Priority 1: -Br (highest atomic number)
     • Priority 2: -CH(…) (group at C3)
     • Priority 3: -CH3
     • Priority 4: -H (lowest atomic number)
  2. Determine configuration: The bromine atom is on a wedge (coming out of the page), so the lowest priority group (-H) is on a dash (going into the page). We trace the path from priority 1 to 2 to 3. This path (Br → C3 → CH3) is counter-clockwise, so the configuration at C2 is S.
• Configuration at C4:
  1. Assign priorities: The four groups on C4 are: -CH(ethyl)CH(Br)CH3 (the rest of the chain at C3), -CH2CH3 (ethyl), -CH3 (methyl), and an implied -H.
     • Priority 1: -CH(…) (group at C3)
     • Priority 2: -CH2CH3 (ethyl)
     • Priority 3: -CH3 (methyl)
     • Priority 4: -H
  2. Determine configuration: The methyl group is on a wedge, so the lowest priority group (-H) is on a dash. Tracing the path from priority 1 to 2 to 3 (C3 → ethyl → methyl) gives a counter-clockwise direction. Therefore, the configuration at C4 is also S.

4. Assemble the Full IUPAC Name:
Finally, we combine all the components. The stereochemical descriptors are placed in parentheses at the beginning of the name, followed by the substituents listed in alphabetical order (bromo, ethyl, methyl), and ending with the parent chain name.

The complete and correct IUPAC name is (2S,4S)-2-bromo-3-ethyl-4-methylhexane