Chemical structure of a branched hydrocarbon with methyl and ethyl substituents.

1. Identify the longest continuous carbon chain: The longest chain contains 8 carbon atoms, so the parent hydrocarbon is octane.
2. Number the carbon atoms in the longest chain to give the substituents the lowest possible numbers: Numbering from left to right gives substituents at positions 3, 4, and 5; numbering from right to left also gives substituents at positions 3, 4, and 5 — both are equivalent.
3. Identify and name the substituents:
- At carbon 3: a tert-butyl group (C(CH₃)₃)
- At carbon 4: an ethyl group (CH₂CH₃)
- At carbon 5: a propyl group (CH₂CH₂CH₃)
4. List substituents in alphabetical order (ignoring prefixes like di-, tri-, tert-): ethyl, propyl, tert-butyl.
5. Assign locants and write the full name: 4-ethyl-5-propyl-3-(tert-butyl)octane.
6. Check for correct naming conventions: Since “tert-butyl” is treated alphabetically under “b”, the correct alphabetical order is ethyl, propyl, tert-butyl. However, IUPAC rules require that complex substituents be named as alkyl groups with their own locants if necessary. The tert-butyl group is acceptable as is.
7. Final IUPAC name: 4-Ethyl-5-propyl-3-(1,1-dimethylethyl)octane (preferred over “tert-butyl” in strict IUPAC).
8. Alternatively, using common names accepted by IUPAC: 4-Ethyl-5-propyl-3-tert-butyloctane.
9. Verify structure matches name: The main chain is octane; substituents are correctly placed on C3, C4, and C5.
10. Confirm no lower numbering is possible: Both directions yield the same set of locants (3,4,5), so it’s optimal.