Identifying the parent chain in IUPAC nomenclature

Steps:

• Examine the given name "3-2-bromo-methylbutane" for errors in structure and numbering.
• Identify the base hydrocarbon chain: "methylbutane" indicates a butane chain with a methyl substituent.
• Recognize that "3-2-bromo" is invalid numbering; the parent is the longest chain, which is butane with a methyl at position 2.
• Correct the name by removing the invalid bromo prefix, yielding 2-methylbutane as the base structure.

Why A is correct:

• In IUPAC rules, the parent chain is the longest continuous carbon chain; here, it's a 4-carbon butane with a methyl branch at carbon 2, forming 2-methylbutane.

Why the others are wrong:

• B: "2-bromo" is incomplete, lacking the full hydrocarbon name required for a compound.
• C: Repeats the original invalid name with improper hyphenation and numbering.
• D: "Bromo-methylbutane" omits locants, violating IUPAC specificity for substituent positions.

Final answer: A