IB Chemistry SL 3.2 Functional Groups Organic Compounds Questions

Practise organic chemistry by translating formula representations, identifying functional groups, naming molecules and isomers, and explaining how structure affects physical properties.

Exam points

Convert between empirical, molecular, displayed, condensed and skeletal formulae without changing connectivity.
Identify functional groups in displayed molecules, including structures that contain more than one group.
Use functional groups to select esterification reactants or identify ester links and products after hydrolysis.
Recognise a homologous series from its functional group and general formula; check members differ by CH₂.
Name or draw structures using IUPAC chain selection, locants and functional-group suffixes (up to six carbons).
Generate or identify isomers sharing a molecular formula but differing in connectivity or functional group.
Classify alcohols, halogenoalkanes and amines as primary, secondary or tertiary from their structures.
Rank boiling points using chain length, branching, molar mass and intermolecular-force strength.
Explain melting-point trends using saturation, cis/trans shape, chain packing and London forces.

Covered syllabus points

3.2.1—Organic formulas 3.2.2—Functional groups 3.2.3—Homologous series 3.2.4—Physical property trends 3.2.5—IUPAC nomenclature 3.2.6—Structural isomers

[Maximum number: 3]

Strychnine, $\mathrm{C}_{21} \mathrm{H}_{22} \mathrm{~N}_{2} \mathrm{O}_{2}\left(M_{\mathrm{r}}=334.4\right)$ , is a white crystalline solid obtained from plants.

(a)

The formula of strychnine is:

Figure for Question (a) — IB Chemistry SL

[ 3 ]

(i)

State the type of structural formula shown.

[ 1 ]

(ii)

State the name of the functional group containing the nitrogen atom labelled "1".

[ 1 ]

(iii)

State the number of rings in strychnine's structure.

[ 1 ]

[Maximum number: 2]

Alkenes, such as A (shown below), are important intermediates in the petrochemical industry because they undergo addition reactions to produce a wide variety of products, such as the conversion shown below.

(a)

Applying IUPAC rules, state the name of A.

[ 1 ]

(b)

In the gas phase, A reacts with hydrogen to form D.

Figure for Question (b) — IB Chemistry SL

[ 1 ]

(i)

State the homologous series to which D belongs.

[ 1 ]

[Maximum number: 2]

$\quad \mathrm{C}_{5} \mathrm{H}_{12}$ exists as three isomers. Identify the structure of the isomer with the lowest boiling point and explain your choice.

$\quad \mathrm{C}\left(\mathrm{CH}_{3}\right)_{4}$ ;

Marking guidance:

Accept correct name 2,2-dimethylpropane.
Do not penalize missing H atoms.
weakest London/dispersion/van der Waals'/vdW/instantaneous induced dipole-induced dipole forces because of smallest surface area/contact
OR
weakest London/dispersion/van der Waals'/vdW/ instantaneous induced dipole-induced dipole forces because of least distortion of the electron cloud OR
weakest London/dispersion/van der Waals'/vdW/ instantaneous induced dipole-induced dipole forces because polarizability of electrons (in electron cloud) is less;

Accept other words to that effect but student must mention a correct IMF and a correct reason.

[Maximum number: 1]

Strychnine, $\mathrm{C}_{21} \mathrm{H}_{22} \mathrm{~N}_{2} \mathrm{O}_{2}\left(M_{\mathrm{r}}=334.4\right)$ , is a white crystalline solid obtained from plants.