Class 11 NEET Chemistry Organic Chemistry Some Basic Principles And Techniques Part 1

Concept: In IUPAC nomenclature, the principal characteristic group (–COOH) gets the lowest possible locant, and the chain is numbered from the end nearest to –COOH.Explanation:Write out the full chain clearly:$$\mathrm{CH_3 - CH = CH - CH_2 - \underset{\displaystyle NH_2}{\underset{|}{CH}} - CH_2 - COOH}$$Step 1: Identify the longest chain containing –COOH and –CH=CH–The chain has 7 carbons (heptanoic acid backbone):| Position | Atom/Group ||----------|-----------|| C-1 | –COOH || C-2 | –CH₂– || C-3 | –CH(NH₂)– || C-4 | –CH₂– || C-5 | –CH= || C-6 | =CH– || C-7 | –CH₃ |Step 2: Number from –COOH end (C-1)

• –COOH is at C-1
• –NH₂ is at C-3 (wait — recount carefully)

Recount from COOH end:$$\underbrace{\mathrm{COOH}}_{1} - \underbrace{\mathrm{CH_2}}_{2} - \underbrace{\mathrm{CH(NH_2)}}_{3} - \underbrace{\mathrm{CH_2}}_{4} - \underbrace{\mathrm{CH}}_{5} = \underbrace{\mathrm{CH}}_{6} - \underbrace{\mathrm{CH_3}}_{7}$$

• –NH₂ at C-3
• Double bond at C-5 (between C-5 and C-6)

Step 3: Name the compound

• Parent chain: hept (7C) + enoic acid (one double bond + acid)
• Double bond: 5-en (between C5–C6)
• Amino group: 3-amino

→ 3-amino-hept-5-enoic acid = 3-amino-5-heptenoic acidAnswer: Option A — *3-amino-5-heptenoic acid*