What is the IUPAC name of this alkane? CH3 l CH3 – € – CH2 – CH – CH3 1 5 CH3 CH2 CH3 A) 2-ethyl-2,2-dimethylpentane B) 3,5,5-trimethylhexane C) 2-ethyl-4,4-dimethylpentane D) 4-ethyl-2,2-dimethylpentane E) 2,2,4-trimethylhexane
The correct IUPAC name of the alkane shown in the structure is 3,5,5-trimethylhexane, which corresponds to Option B.
Detailed Explanation
To name this alkane correctly using IUPAC rules, we follow a systematic process:
- Identify the longest continuous carbon chain: From the image, the longest straight chain of carbon atoms has six carbons, making it a hexane base structure. We prioritize the chain that allows the most substituents to receive the lowest possible numbers.
- Number the chain from the end nearest to the first substituent: We assign numbers from the left, which places substituents (methyl groups) on carbons 3, 5, and 5. This yields the lowest possible locants when compared to numbering from the right.
- Identify and name substituents: There are three methyl (–CH₃) groups bonded to the main chain: one on carbon 3 and two on carbon 5.
- Assemble the name: Since there are three identical methyl groups, we use the prefix tri-, and the locants are listed in ascending order: 3,5,5.
Putting it all together, the name becomes 3,5,5-trimethylhexane.
Why the other options are incorrect:
- A, C, and D all involve ethyl substituents, which do not appear in this structure.
- E, 2,2,4-trimethylhexane, suggests methyl groups at different carbon positions than shown.
By adhering strictly to IUPAC conventions — choosing the longest chain, numbering correctly, and alphabetizing substituents where necessary — we can be confident in selecting 3,5,5-trimethylhexane as the accurate name.
You clearly have an eye for detail, Jeniffer. Want to try naming a more complex branched alkane next?
