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IB Chemistry HL 3.2 Functional Groups Organic Compounds Questions

Practise organic chemistry from formulae, functional groups and isomers, then interpret stereochemistry, mass spectra, IR and proton-NMR data to justify structures.

Syllabus
First assessment 2025
Course
Chemistry HL
Level
HL

Exam points

  • Convert between molecular/empirical and structural or skeletal formulae without changing connectivity.
  • Identify functional groups in organic structures and explain esterification, hydrolysis or acid–base behaviour.
  • Classify compounds by functional group and general formula, checking that homologues differ by CH₂.
  • Name or draw compounds up to six carbons using IUPAC chain priority, locants and functional-group suffixes.
  • Generate structural isomers from a formula and classify alcohol, halogenoalkane or amine centres by connectivity.
  • Identify chiral centres and use 3D, R/S or optical evidence to distinguish E/Z isomers from enantiomers.
  • Rank boiling points by molecular size, branching and intermolecular forces such as hydrogen bonding.
  • Explain melting-point differences from saturation, cis/trans geometry, chain packing and London forces.
  • Use molecular-ion and isotope peaks to infer relative mass or formula, then assign fragments from m/z values.
  • Match IR wavenumber ranges and missing bands to bonds or functional groups in candidate structures.
  • Use ¹H NMR signal count, shifts, integration and splitting to identify proton environments and neighbours.
  • Combine MS, IR and ¹H NMR evidence to constrain candidate structures and justify an identification.

Covered syllabus points

3.2.1—Organic formulas3.2.2—Functional groups3.2.3—Homologous series3.2.4—Physical property trends3.2.5—IUPAC nomenclature3.2.6—Structural isomers3.2.7 (HL)—Stereoisomers3.2.8 (HL)—Mass spectrometry3.2.9 (HL)—Infrared spectroscopy3.2.10 (HL)—¹H NMR spectroscopy3.2.11 (HL)—NMR splitting patterns3.2.12 (HL)—Combined data analysis

Question 1

[Maximum number: 2]

Question (a)

(a)

An organic compound, X, with a molar mass of approximately 88 g mol−188 \mathrm{~g} \mathrm{~mol}^{-1} contains 54.5 % carbon, 36.3 % oxygen and 9.2 % hydrogen by mass.

[ 2 ]

Question (i)

(i)

X is a straight-chain carboxylic acid. Draw its structural formula.

[ 1 ]

Question (ii)

(ii)

Draw the structural formula of an isomer of X which is an ester.

[ 1 ]

Question 2

[Maximum number: 9]

Organic compounds have many industrial applications.

Question (a)

(a)

The following organic compound, X, is used as a flavouring agent.

Figure for Question (a) — IB Chemistry HL
[ 5 ]

Question (i)

(i)

State the name of the functional group present in X.

[ 1 ]

Question (ii)

(ii)

Deduce the systematic name of X using IUPAC nomenclature.

[ 1 ]

Question (iii)

(iii)

Deduce the number of signals and their relative areas (integration traces) in an 1H{ }^{1} \mathrm{H} NMR spectrum of X.

Number of signals:
Relative areas:

[ 2 ]

Question (iv)

(iv)

Draw an isomer of X which belongs to a different homologous series.

[ 1 ]

Question (b)

(b)

An alkene such as ethene can be used as starting material for a range of compounds.

[ 1 ]

Question (i)

(i)

State the general formula for the homologous series of alkenes.

[ 1 ]

Question (c)

(c)

The chloroalkene with the formula C4H7Cl\mathrm{C}_{4} \mathrm{H}_{7} \mathrm{Cl} can exist as several stereoisomers.

[ 3 ]

Question (i)

(i)

Draw the structural formula of cis-1-chlorobut-2-ene.

[ 1 ]

Question (ii)

(ii)

Deduce the structure of a chloroalkene, C4H7Cl\mathrm{C}_{4} \mathrm{H}_{7} \mathrm{Cl}, that can exhibit optical isomerism, and identify the chiral carbon atom with an asterisk (*).

[ 2 ]
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