Question

Which of the following IUPAC name is (are) incorrect? (A) 1 -Amino pentan-1-one (B) 2-Methyl pentan-5-ol (C) 3-Carboxy pentane (D) 1 -Bromo-3-chloro-4-iodo cyclohexane

Short answer

The incorrect IUPAC names are options (A) 1-Amino pentan-1-one and (C) 3-Carboxy pentane. The correct names should be 5-Amino pentan-1-one and pentanoic acid (or 3-methyl butanoic acid), respectively.

Step-by-step solution

Check option (A) - 1-Amino pentan-1-one

1-Amino pentan-1-one has both an amino group (-NH2) and a ketone group (C=O) on the pentane chain. According to the IUPAC convention, functional groups should be numbered from the smallest for highest priority. Since carbonyl has higher priority compared to the amino group, the IUPAC name should be 5-Amino pentan-1-one. So, option (A) is incorrect.

Check option (B) - 2-Methyl pentan-5-ol

2-Methyl pentan-5-ol has a methyl group at the second carbon and an alcohol group (OH) at the last carbon. The numbering of the functional groups in the name is correct, and therefore option (B) is correct.

Check option (C) - 3-Carboxy pentane

3-Carboxy pentane has a carboxy group (COOH) at the third carbon. The proper IUPAC term to indicate a carboxyl group on a hydrocarbon chain is "oic acid" and not "carboxy". So, the correct IUPAC name should be pentanoic acid, or 3-methyl butanoic acid if the carboxyl group is placed at the third carbon. Thus, option (C) is incorrect.

Check option (D) - 1-Bromo-3-chloro-4-iodo cyclohexane

1-Bromo-3-chloro-4-iodo cyclohexane has three halogen atoms (bromine, chlorine, and iodine) attached to the cyclohexane ring. The numbering of the halogens is consistent with the IUPAC rules for numbering the functional groups in a cyclohexane ring. The functional groups are correctly ordered alphabetically in the name. So, option (D) is correct. In summary, options (A) and (C) are the incorrect IUPAC names.