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Naming questions in Class 10 come in two directions. Some give you a structure and ask for the name. Others, like NCERT's "Draw the structures for... butanone... hexanal", give you the name and ask for the structure. Most practice covers only the first. This post works through both directions with examples beyond the three-carbon ones in the textbook table, and ends with a practice routine that mixes them.
What does the syllabus ask for?
The CBSE Secondary curriculum for 2026-27 lists "Nomenclature of alkanes, alkenes, alkyne and carbon compounds containing functional groups (halogens, alcohol, ketones, aldehydes)" under Carbon and its Compounds. The method is in section 4.2.5 of Chapter 4 of the NCERT Class 10 Science textbook (2026-27 reprint). Carboxylic acids are in NCERT's naming table too, so learn them with the rest. For a wider tour of the chapter, including reactions, see our Class 10 carbon compounds guide.
How is a Class 10 name built?
A name has a root and an ending. The root counts carbons in the chain: meth (1), eth (2), prop (3), but (4), pent (5), hex (6). The ending tells you the functional group, from NCERT's Table 4.4:
Halogen: prefix chloro or bromo (bromopropane).
Alcohol: suffix -ol (propanol).
Aldehyde: suffix -al (propanal).
Ketone: suffix -one (propanone).
Carboxylic acid: suffix -oic acid (propanoic acid).
Double bond: -ane becomes -ene (propene). Triple bond: -ane becomes -yne (propyne).
One spelling rule: if the suffix begins with a vowel, drop the final "e" of the alkane name. Propane plus -one gives propanone, not propaneone. A prefix needs no change, so it is bromopropane.
Naming has a purpose beyond the exam. IUPAC's Nomenclature of Organic Chemistry (2013) explains that a systematic name has a relationship to the structure "in order that the reader or listener can deduce the structure from the name." That is the skill the name-to-structure questions test.
Worked examples: from name to structure
Butanone. "But" means four carbons. "-one" means a ketone, so the C=O must sit on a carbon with a carbon on each side. Structure: CH₃–CO–CH₂–CH₃. Count: C₄H₈O. Check every carbon has four bonds.
Hexanal. Six carbons, aldehyde. The –CHO group is always at the end of the chain, and its carbon is one of the six. Structure: CH₃–CH₂–CH₂–CH₂–CH₂–CHO, formula C₆H₁₂O.
Bromopentane. Five carbons with one bromine replacing a hydrogen: CH₃–CH₂–CH₂–CH₂–CH₂–Br. NCERT then asks whether structural isomers are possible. Yes. On the straight chain, the bromine can sit on the first, second or third carbon; the fourth and fifth repeat the second and first from the other end. That gives three different compounds before you even branch the chain. In Class 11 you will tell them apart with numbers (1-bromopentane, 2-bromopentane, 3-bromopentane).
Worked examples: from structure to name
CH₃–CH₂–CH₂–COOH. Four carbons, including the one in –COOH. Carboxylic acid. Name: butanoic acid.
CH₃–CH₂–CH₂–CH₂–OH. Four carbons, alcohol. Butane minus "e" plus "ol": butanol.
HCHO. One carbon, aldehyde: methanal.
CH₃–CH₂–C≡CH. Four carbons, triple bond: butyne.
CH₃–CH₂–CH₂–Cl. Three carbons, chlorine as a prefix: chloropropane.
Why is there no ethanone?
A ketone's C=O carbon must be bonded to two other carbons. With two carbons in total, the C=O carbon can have only one neighbour, which makes it an aldehyde (ethanal, CH₃CHO). The smallest ketone is therefore propanone. If you ever write ethanone or methanone, stop and recount.
This also explains a classic isomer question. Propanal (CH₃CH₂CHO) and propanone (CH₃COCH₃) both have the formula C₃H₆O. Same atoms, different functional groups, different names. A quick check: aldehydes and ketones fit CₙH₂ₙO, and acids fit CₙH₂ₙO₂.
Which mistakes cost marks?
Missing the carbon in –CHO or –COOH. Count it.
Dropping the "e" before a consonant. It is propene and bromopropane; the "e" goes only before -ol, -al, -one and -oic acid.
Putting -al in the middle of a chain. An aldehyde group is always at a chain end. In the middle, a C=O is a ketone.
Confusing ethanol and ethanoic acid. -ol is the alcohol; -oic acid has the –COOH group.
Writing structures with five bonds on a carbon. Count four bonds per carbon after every structure.
A practice routine that mixes both directions
Mixing problem types makes you choose the method rather than repeat it. In a classroom study of 126 seventh-grade maths students, Rohrer, Dedrick and Stershic (2015) found that interleaved practice produced higher scores than blocked practice on tests one day and 30 days later.
Write 16 cards: eight names on some (two each of alcohols, aldehydes, ketones and acids, from two to six carbons) and eight structures on the others.
Shuffle them together. For a name, draw the structure; for a structure, write the name.
After each, write the molecular formula and check it against the general formula.
Repeat the cards you missed the next day, and add two new ones.
If you get one wrong and cannot see why, the Fermi Problem Library has a step-by-step solver that explains the reasoning rather than printing an answer. Once you move to Class 11 numbering, our guide to IUPAC naming takes the same ideas further.
Today, draw butanone, hexanal and pentanoic acid from their names, then count the carbons in each.
