Nomenclature of Organic Compounds (NCERT) - Free MCQ Practice Test

Option D is correct.

For structure (i), identify the longest continuous carbon chain: it contains 5 carbon atoms, so the parent hydrocarbon is pentane.

Number the carbon chain from the end nearer the substituent so the substituent receives the lowest possible locant. A methyl substituent lies on carbon 3, giving the correct IUPAC name 3-methylpentane.

For structure (ii), the longest continuous carbon chain contains 4 carbon atoms, so the parent hydrocarbon is butane.

Number the chain to assign the lowest locant to the substituent. The methyl group is on carbon 2, giving the correct IUPAC name 2-methylbutane.

Therefore the pair of IUPAC names is 3-methylpentane and 2-methylbutane, matching option D.

To determine the IUPAC name of the given compound, follow these steps:

1. Identify the longest carbon chain: The longest continuous chain has 8 carbon atoms, so the base name is octane.
2. Number the chain: Number the carbon chain from the end nearest to the first substituent to give the substituents the lowest possible numbers.
3. Identify substituents and their positions:
   • At carbon 3, there is a methyl (-CH₃) group.
   • At carbon 4, there is an ethyl (-CH₂CH₃) group.
4. Write the name: Substituents are listed alphabetically regardless of their position numbers.
   • Ethyl comes before methyl alphabetically.
   • Therefore, the name is 4-ethyl-3-methyloctane.

Hence, the correct IUPAC name of the compound is 4-ethyl-3-methyloctane.

Answer: D. 4-ethyl-3-methyloctane

1° - 5, 2° - 1, 3° - 1, 4° - 1

Answer: (b), The IUPAC name of aforementioned compound is 3,3 –dimethyl -1-cyclohexanol.

The order of preference of functional groups is as follows;

The correct name is 3-methylbutan-2-ol since functional group should get lowest number.

4-Hydroxy-2-methylpent-2-en-l-al

2-formyl-3-oxopentanenitrile

Why:

• Treat the –C≡N carbon as C-1 (nitrile = parent suffix -nitrile).

• That gives a five-carbon parent chain (pentanenitrile).

• The terminal aldehyde (original –CHO) is now a formyl substituent at C-2 → 2-formyl.

• The carbonyl (=O) in the chain is a 3-oxo substituent.

• Assemble substituents alphabetically: formyl before oxo → 2-formyl-3-oxopentanenitrile.

For comparison (non-preferred/older style): the same structure can be called 2-cyano-3-oxopentanal (aldehyde as parent), but that is not the preferred IUPAC name under the modern rules.

Option C is not correctly matched.

The name 1,1-dimethylcyclohexane indicates two methyl groups bonded directly to the same ring carbon (a geminal dimethyl substitution on the cyclohexane ring).

The drawn structure, however, corresponds to a single carbon attached to the ring that itself carries two methyl groups; that carbon is an alkyl substituent (the propan-2-yl group, commonly called isopropyl), not two separate methyl substituents on the ring carbon.

By selecting the larger group as parent, the ring is chosen as parent. The correct systematic name is therefore 1-(propan-2-yl)cyclohexane (equivalently propan-2-ylcyclohexane or isopropylcyclohexane), so the given name 1,1-dimethylcyclohexane is incorrect.

Hence the incorrectly matched option is C.

Priority of functional groups is
- COOH > - CHO >>C = O.
Hence, the lUPAC name is 4-formyl-2-oxocyclohexane carboxylicacid.

1-chloro-2,4-dinitrobenzene is the correct iupac name of this compound 

• Chlorine (Cl) is assigned position 1 because it comes first alphabetically.
• Nitro groups (NO₂) are numbered 2 and 4 to give the lowest possible locants.
• The name follows the order: 1-chloro-2,4-dinitrobenzene, listing substituents alphabetically and indicating their positions.