Find the parent chain, then name it
"Find the parent chain, then name it" is a free, interactive Class 11 Chemistry simulation for NEET and JEE, built on the NCERT section "IUPAC nomenclature" in Organic Chemistry – Some Basic Principles and Techniques. Trace the longest chain through a branched skeleton by tapping carbons; the sim numbers it from both ends, compares locant sets and assembles the alphabetised name. NEET has asked about this idea 3 times in 10 years of papers. JEE Main asked 91 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
From the lesson IUPAC nomenclature in Organic Chemistry – Some Basic Principles and Techniques. Change the values and watch what happens.
What it shows
NCERT § "Nomenclature of Organic Compounds"
Trace the longest chain through a branched skeleton by tapping carbons; the sim numbers it from both ends, compares locant sets and assembles the alphabetised name.
Controls
3 to try
- Tapcarbons to trace a chain
- Togglenumber from left / right
- Segmentedmolecule (6 branched examples incl. one alkene with Br)
Try this
Name (CH3)2CH–CH2–CH2–CH3 by choosing the five-carbon parent and the end that gives 2-methylpentane.
Common mistake
Total carbons taken as the parent; halogen given a lower locant than the double bond.
In NEET
10 years of papers
Asked 3 times in 10 years of NEET.
See the past questions: Organic Nomenclature, Organic Chemistry - Some Basic Principles and Techniques (chapter)
In JEE Main
42 shifts analysed
91 questions from Organic Chemistry – Some Basic Principles and Techniques across the 42 JEE Main shifts Lumi has analysed (2017–2026).
The idea behind it
NCERT § "Nomenclature of Organic Compounds"
- An IUPAC name is built from a root word (length of the parent chain), a primary suffix (ane, ene, yne), a secondary suffix for the principal functional group and prefixes for substituents.
- Choose the longest carbon chain as the parent; if two chains are equally long, choose the one with more substituents.
- Number the chain so that the substituents (or the principal group, or multiple bonds) get the lowest set of locants.
- Substituent prefixes are written in alphabetical order; multiplying prefixes such as di-, tri- and tetra- are ignored when alphabetising.
- When several functional groups are present, the principal group takes the suffix; the order of preference is –COOH > –SO₃H > –COOR > –COCl > –CONH₂ > –CN > –CHO > >C=O > –OH > –NH₂ > >C=C< > –C≡C–.
- Halogens (–F, –Cl, –Br, –I), –NO₂ and –OR are always written as prefixes (fluoro, chloro, bromo, iodo, nitro, alkoxy), never as suffixes.
- Example: CH₂=CH–CH₂–CHBr–CH₃ is numbered from the end nearer the double bond, giving 4-bromopent-1-ene rather than 2-bromopent-4-ene.
- Ring compounds take the prefix cyclo-, as in cyclohexane.
- In disubstituted benzenes, 1,2-, 1,3- and 1,4- positions are also called ortho (o-), meta (m-) and para (p-).
Questions
5 answers
- What does the "Find the parent chain, then name it" simulation show?
- Trace the longest chain through a branched skeleton by tapping carbons; the sim numbers it from both ends, compares locant sets and assembles the alphabetised name.
- What mistake does the "Find the parent chain, then name it" simulation fix?
- A common mistake it clears up: total carbons taken as the parent; halogen given a lower locant than the double bond.
- Has NEET asked about this idea?
- Yes. NEET has asked about this idea 3 times in 10 years of papers.
- Does JEE Main ask questions from Organic Chemistry – Some Basic Principles and Techniques?
- Yes. JEE Main asked 91 questions from this chapter across the 42 shifts Lumi has analysed (2017–2026).
- Is this simulation free?
- Yes. It is free and runs in the browser on a phone or a laptop. It belongs to the lesson "IUPAC nomenclature" in Organic Chemistry – Some Basic Principles and Techniques (Class 11 Chemistry).
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