The pair of molecules that are metamers among the following is :

Core Logic

In an organic compound, elements like Nitrogen, Sulphur, and Halogens are bonded to Carbon via covalent bonds. During Lassaigne's test, the organic compound is fused with sodium metal. The high temperature and reactive sodium break the covalent bonds and convert these elements into water-soluble ionic sodium salts.

• Carbon and Nitrogen form Sodium Cyanide (NaCN$NaCN$)
• Sulphur forms Sodium Sulphide (Na₂S$Na_2S$)
• Halogens form Sodium Halides (NaX$NaX$)

Step 1: Final Conclusion

The elements are converted from covalent form to ionic form to facilitate their detection using standard inorganic qualitative analysis.

Pattern Recognition

Sodium extract preparation (Lassaigne's fusion) always serves to ionize covalently bonded organic heteroatoms into inorganic sodium salts.

Chapter Mix

Class 11 Chemistry: Organic Chemistry - Some Basic Principles and Techniques

Core Logic

Step 1: Identify the longest carbon chain. The longest continuous chain containing both substituents has 7 carbon atoms (heptane). Step 2: Number the chain to give the lowest possible locants to the substituents. Numbering from left to right gives substituents at positions 3 (ethyl) and 5 (methyl). Numbering right to left gives 3 (methyl) and 5 (ethyl). When locant sets are equivalent (3,5), alphabetical priority governs the numbering. 'Ethyl' comes before 'Methyl', so the ethyl group gets the lower number (3). Substituents: 3-ethyl and 5-methyl.

Step 1: Final Name

The correct IUPAC name is 3-ethyl-5-methylheptane.

Pattern Recognition

Always choose the longest chain first. If numbering from both ends yields the same locant set, default to alphabetical order for deciding which end starts at 1.

Chapter Mix

Class 11 Chemistry: Organic Chemistry - Some Basic Principles and Techniques