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.

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 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 3.2.7 (HL)—Stereoisomers 3.2.8 (HL)—Mass spectrometry 3.2.9 (HL)—Infrared spectroscopy 3.2.10 (HL)—¹H NMR spectroscopy 3.2.11 (HL)—NMR splitting patterns 3.2.12 (HL)—Combined data analysis

[Maximum number: 2]

(a)

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

[ 2 ]

(i)

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

[ 1 ]

$\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{COOH}$ ;

(ii)

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

[ 1 ]

$\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{COOCH}_{3} / \mathrm{CH}_{3} \mathrm{COOCH}_{2} \mathrm{CH}_{3} / \mathrm{HCOOCH}_{2} \mathrm{CH}_{2} \mathrm{CH}_{3} / \mathrm{HCOOCH}\left(\mathrm{CH}_{3}\right)_{2}$ ;

[Maximum number: 9]

Organic compounds have many industrial applications.

(a)

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

Figure for Question (a) — IB Chemistry HL

[ 5 ]

(i)

State the name of the functional group present in X.

[ 1 ]

(ii)

Deduce the systematic name of X using IUPAC nomenclature.

[ 1 ]

(iii)

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

Number of signals:
Relative areas:

[ 2 ]

(iv)

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

[ 1 ]

Figure for Answer to Question (iv) — IB Chemistry HL

OR

Accept any ketone, unsaturated alcohol/ether or cyclic alcohol/ether, with molecular formula $\mathrm{C}_{9} \mathrm{H}_{18} \mathrm{O}$ .

Accept any correct representation including skeletal structures.

Ignore connectivity of methyl groups

(b)

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

[ 1 ]

(i)

State the general formula for the homologous series of alkenes.

[ 1 ]

$\mathrm{C}_{\mathrm{n}} \mathrm{H}_{2 \mathrm{n}}$

Subscripts of numbers not
essential

(c)

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

[ 3 ]

(i)

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

[ 1 ]

(ii)

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

[ 2 ]

Figure for Answer to Question (ii) — IB Chemistry HL

$\mathrm{CH}_2=\mathrm{CH}-\mathrm{CH}^{*}(\mathrm{Cl})-\mathrm{CH}_3$

correct isomer
chiral C

Accept any correct representation including skeletal structures.
Accept any correct indication of chiral carbon.

[Maximum number: 6]

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)

B can be converted into C.

[ 4 ]

(i)

Explain why C would not be optically active.

[ 2 ]

(ii)

Deduce the structural formula of an isomer of C that would be optically active and could also be oxidized to a carboxylic acid by acidified potassium dichromate(VI).

[ 2 ]

primary alcohol with formula $\mathrm{C}_{6}\mathrm{H}_{13}\mathrm{OH}$ ;
optically active compound with formula $\mathrm{C}_{6}\mathrm{H}_{13}\mathrm{OH}$ ;

(b)

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

Figure for Question (b) — IB Chemistry HL

[ 2 ]

(i)

Compound D is isomeric with hexane. Predict, giving reasons, how the boiling points of these compounds would compare.

[ 2 ]

[Maximum number: 1]

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

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

$\mathrm{CH}_{3} \mathrm{CH}_{2} \mathrm{CH}_{2} \mathrm{COOH}$ ;

[Maximum number: 1]

Organic compounds have many industrial applications.

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

State the name of the functional group present in X.

[Maximum number: 1]

Organic compounds have many industrial applications.

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

State the general formula for the homologous series of alkenes.

$\mathrm{C}_{\mathrm{n}} \mathrm{H}_{2 \mathrm{n}}$

Subscripts of numbers not
essential

[Maximum number: 2]

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

Compound D is isomeric with hexane. Predict, giving reasons, how the boiling points of these compounds would compare.

[Maximum number: 1]

Organic compounds have many industrial applications.

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

Deduce the systematic name of X using IUPAC nomenclature.

[Maximum number: 1]

Organic compounds have many industrial applications.

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

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

Figure for Answer to Question 9 — IB Chemistry HL

[Maximum number: 2]

Urea, $\left(\mathrm{H}_{2} \mathrm{~N}\right)_{2} \mathrm{CO}$ , is excreted by mammals and can be used as a fertilizer.

The mass spectrum of urea is shown below.

Figure for Question 10 — IB Chemistry HL

Reference Database Number 69, Eds. P.J. Linstrom and W.G. Mallard, National Institute of Standards and Technology, Gaithersburg MD, 20899, doi:10.18434/T4D303, (retrieved May 31, 2018).]

Identify the species responsible for the peaks at m / z=60 and 44 .

60:

44:

60: $\mathrm{CON}_{2} \mathrm{H}_{4}{ }^{+}$

44: $\mathrm{CONH}_{2}{ }^{+}$

[Maximum number: 2]

Urea, $\left(\mathrm{H}_{2} \mathrm{~N}\right)_{2} \mathrm{CO}$ , is excreted by mammals and can be used as a fertilizer.

The IR spectrum of urea is shown below.

Figure for Question 11 — IB Chemistry HL

Identify the bonds causing the absorptions at $3450 \mathrm{~cm}^{-1}$ and $1700 \mathrm{~cm}^{-1}$ using section 26 of the data booklet.

$3450 \mathrm{~cm}^{-1}$ :

$1700 \mathrm{~cm}^{-1}$ :

[Maximum number: 2]

Organic compounds have many industrial applications.

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

Figure for Question 12 — IB Chemistry HL

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

Number of signals:
Relative areas:

[Maximum number: 1]

Urea, $\left(\mathrm{H}_{2} \mathrm{~N}\right)_{2} \mathrm{CO}$ , is excreted by mammals and can be used as a fertilizer.

Predict the splitting pattern of the ${ }^{1} \mathrm{H}$ NMR spectrum of urea.

[Maximum number: 3]

This question is about carbon and chlorine compounds.

The mass and ${ }^{1} \mathrm{H}$ NMR spectra of product X are shown below. Deduce, giving your reasons, its structural formula and hence the name of the compound.

Mass spectrum:

Figure for Question 14 — IB Chemistry HL

${ }^{1} \mathrm{H}$ NMR spectrum:

molecular ion peak(s) about m/z 100 AND so $\mathrm{C}_{2}\mathrm{H}_{4}\mathrm{Cl}_{2}$ (isotopes of Cl)

two signals in ${ }^{1} \mathrm{H}$ NMR spectrum AND so $\mathrm{CH}_{3}\mathrm{CHCl}_{2}$

OR

signals in 3:1 ratio in ${ }^{1} \mathrm{H}$ NMR spectrum AND so $\mathrm{CH}_{3}\mathrm{CHCl}_{2}$

OR

one doublet and one quartet in ${ }^{1} \mathrm{H}$ NMR spectrum AND so $\mathrm{CH}_{3}\mathrm{CHCl}_{2}$

1,1-dichloroethane

All question bank results loaded

Covered syllabus points

Question 1

Question (a)

Question (i)

Question (ii)

Question 2

Question (a)

Question (i)

Question (ii)

Question (iii)

Question (iv)

Question (b)

Question (i)

Question (c)

Question (i)

Question (ii)

Question 3

Question (a)

Question (i)

Question (ii)

Question (b)

Question (i)

Question 4

Question 5

Question 6

Question 7

Question 8

Question 9

Question 10

Question 11

Question 12

Question 13

Question 14