Quick answer: IUPAC nomenclature names an organic compound from its longest carbon chain, its functional group and its substituents, with numbers giving their positions. This Chemistry 11-12 worksheet on organic nomenclature gives 20 problems from easy to hard: alkane names and formulae, name the straight chains and condensed formulae. The worked answers are on a separate page, and the worksheet is a free printable PDF.
These 20 problems build your skill in IUPAC naming, drawing and counting isomers, assigning E and Z, and finding chiral centres. They mix recall, naming, calculation and explanation tasks.
They suit A Level, IB Chemistry, CBSE Class 11-12 and WAEC or NECO senior students. Write condensed or skeletal formulae clearly.
Level: Chemistry grades 11-12 (A Level · IB · Class 11-12) · Curriculum: IB S3.2
Problem 1 Alkane names and formulae ★★★
1. Name the straight-chain alkanes with 1 to 6 carbon atoms.2. State the general formula of the alkanes.
3. Write the molecular formula of heptane.
Problem 2 Name the straight chains ★★★
Name each compound.1. CH₃CH₂CH₂CH₂CH₂OH
2. CH₃CH₂CHO
3. CH₃COCH₂CH₃
4. CH₃CH₂COOH
Problem 3 Condensed formulae ★★★
1. Write the condensed formula of 2-methylbutane.2. Write the condensed formula of 2,2-dimethylpropane.
3. State the molecular formula of both.
Problem 4 Identify functional groups ★★★
Name the functional groups in: CH₂=CHCH₂OH, CH₃COOCH₃, CH₃CH₂NH₂ and CH₃CH₂Cl.Problem 5 Which type of isomerism ★★★
State the type of structural isomerism in each pair.1. butan-1-ol and butan-2-ol
2. butane and 2-methylpropane
3. propanal and propanone
4. ethanol and methoxymethane
Problem 6 Branched names ★★★
Name each compound.1. (CH₃)₃CCH₂CH₃
2. CH₃CHClCH₂CH₃
3. CH₃CH(CH₃)CH(CH₃)CH₂CH₃
4. CH₃CH₂CHBrCH₂CH₃
Problem 7 Isomers of C₄H₉Br ★★★
Aarav in Pune draws the isomers of C₄H₉Br.1. Name all four structural isomers.
2. Classify each as primary, secondary or tertiary.
Problem 8 Boiling points of C₅H₁₂ isomers ★★★
The boiling points are pentane 36 °C, 2-methylbutane 28 °C and 2,2-dimethylpropane 10 °C.1. Calculate the difference between the highest and lowest.
2. Explain the trend in terms of branching and London forces.
Problem 9 E and Z but-2-ene ★★★
1. Label each as E or Z.
2. Explain why but-1-ene has no E/Z isomers.
3. Explain why rotation about C=C is restricted.
Problem 10 Chiral or not ★★★
Decide which of these are chiral and mark the chiral centre: butan-1-ol, pentan-3-ol, 3-methylhexane, 1-chlorobutane, 2-bromopentane, 2-chloropropane.Problem 11 Combustion analysis ★★★
A hydrocarbon (0.2200 g) burns to give 0.6600 g of CO₂ and 0.3600 g of H₂O (Ar: C 12.0, H 1.0, O 16.0).1. Calculate n(C) and n(H).
2. Find the empirical formula.
3. State the number of structural isomers if Mr = 44.
Problem 12 Enantiomeric excess ★★★
A pure enantiomer rotates plane-polarised light by +20.0°. A mixture of both enantiomers rotates it by +5.0°.1. Calculate the enantiomeric excess.
2. Calculate the percentage of each enantiomer.
Problem 13 Formula from percentages ★★★
Compound X has 54.5 % C, 9.1 % H and 36.4 % O by mass and Mr = 88.1. Find the empirical formula.
2. Find the molecular formula.
3. Name any two isomers of X with a carboxylic acid or ester group.
Problem 14 Alkenes and alkynes ★★★
Name each compound.1. CH₃C≡CCH₃
2. CH₂=C(CH₃)CH₂CH₃
3. CH₃CH=CHCH₂CH₃
4. HC≡CCH₂CH₃
Problem 15 Spot the errors ★★★
Emma in Leeds wrote three statements. Identify and correct each error.1. CH₃CH(CH₂CH₃)CH₂CH₃ is 2-ethylbutane.
2. CH₃CH₂CH(OH)CH₃ is butan-3-ol.
3. In a Z isomer the higher-priority groups are on opposite sides.
Problem 16 Assign E or Z ★★★
1. Rank the groups on the left carbon and on the right carbon.
2. Decide whether Q is E or Z.
3. Draw (describe) the other isomer.
Problem 17 Lactic acid ★★★
1. Identify the chiral carbon and the four groups.
2. State two properties that are identical in the two enantiomers and one that differs.
3. Explain why a lab synthesis normally gives a racemic mixture.
Problem 18 Isomers of C₄H₈ ★★★
Diego in Texas investigates C₄H₈.1. Name three alkene isomers and one cycloalkane isomer.
2. State which alkene isomer shows E/Z isomerism.
3. Count the total number of stereo- and structural isomers, including cycloalkanes.
Problem 19 Isomers of C₃H₆O₂ ★★★
Mei in Singapore has a liquid of formula C₃H₆O₂ that effervesces with sodium carbonate.1. Name the compound.
2. Name two isomers that do not effervesce, with the type of isomerism.
3. Explain a test to distinguish the acid from an ester.
Problem 20 Name complex structures ★★★
Name or draw.1. HOCH₂CH(CH₃)CH₂CHClCH₃
2. (CH₃)₂C=CHCH₂CH₃
3. CH₃CH(CH₃)CH₂COOH
4. Write the condensed formula of 2,3-dichloro-3-methylpentane.
5. Calculate the maximum number of stereoisomers of 2,3-dibromopentane.
