IB Chemistry HL 3.4.13 Electrophilic substitution in benzene Question Bank

Practise IB Chemistry HL 3.4.13 by applying electrophilic substitution in benzene to exam-style questions.

Exam points

identify the relevant chemical structure, process or evidence
apply the correct chemical model or equation
evaluate the result using chemical reasoning and data

[Maximum number: 7]

Benzene is an aromatic hydrocarbon.

(a)

State the typical reactions that benzene and cyclohexene undergo with bromine.
Benzene:
Cyclohexene:

[ 1 ]

benzene: «electrophilic» substitution/ $\mathrm{S}_{\mathrm{E}}$

AND

cyclohexene: «electrophilic» addition/ $\mathrm{A}_{\mathrm{E}}$

Marking guidance:

Accept correct equations.

(b)

State the reagents used to convert benzene to nitrobenzene and the formula of the electrophile formed.

[ 2 ]

«concentrated» nitric AND sulfuric acids

${ }^{+} \mathrm{NO}_{2}$

Marking guidance:

Accept $\mathrm{NO}_{2}{ }^{+}$ .

(c)

Explain the mechanism for the nitration of benzene, using curly arrows to show the movement of electron pairs.

[ 4 ]

curly arrow going from benzene ring to N of ${ }^{+} \mathrm{NO}_{2} / \mathrm{NO}_{2}{ }^{+}$ carbocation with correct formula and positive charge on ring curly arrow going from C-H bond to benzene ring of cation formation of organic product AND $\mathrm{H}^{+}$

Marking guidance:

Accept mechanism with corresponding Kekulé structures.

Do not accept a circle in M2 or M3.

Accept first arrow starting either inside the circle or on the circle.

M2 may be awarded from correct diagram for M3.

M4: Accept $\mathrm{C}_{6} \mathrm{H}_{5} \mathrm{NO}_{2}+\mathrm{H}_{2} \mathrm{SO}_{4}$ if $\mathrm{HSO}_{4}{ }^{-}$ used in M3.

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3.4.13 (HL)—Electrophilic substitution in benzene question 1

Question (a)

Question (b)

Question (c)