F324 Arenes Homework (MS)
1.	delocalised electrons
electrons are spread over more than two atoms AW (1)
	π-bond
formed by overlap of p-orbitals/ diagram to show (1)	2
[2]
 
2.	(a)	any two of …
fibres / dyes / explosives / pharmaceuticals etc (1)(1)	2
allow any specific examples as long as they do involve aromatic nitro or amine groups – eg NOT nylon, fertiliser etc
(b)	temp 50-60° (1)
concentrated (acids) (1)	2
allow abbreviations for concentrated
(c)	C6H6 + HNO3 → C6H5NO2 + H2O
reactants (1)	products (1)	2
allow a balanced equation for multiple nitration at any positions
(d)	(i)	a pair of electrons … (1)
… (electrons) move / transferred /
a (covalent) bond breaks/forms (1)	2
(ii)	it accepts a pair of electrons (from the benzene) (1)	1
NOT a ‘lone’ pair
(iii)	H(+) (on the ring) is replaced by NO2(+) (1)	1
allow ‘substitutes’
ignore + charges
(iv)	it is not used up / reformed at the end AW (1)	1
 (e)	π-bonding electrons are delocalised (1)
	six π-electrons in benzene (1)
four π-electrons in the intermediate (1)
	π-electrons are not over one carbon atom /
over five carbon atoms / p-orbitals in the intermediate (1)
this must be stated in words to compare benzene and the intermediate
	π-electrons are over the complete ring / all around the ring
all six carbon atoms/ p-orbitals overlapping (1)
	Quality of written communication
for at least two sentences/statements with legible text and
correct spelling, punctuation and grammar (1)	6
[17]

 

3.	(a)	(i)
 (1)	1
(ii)	Introduces a permanent dipole on Cl2 / forms Cl+/
AlCl3 + Cl2 → AlCl4– + Cl+/
AlCl3 + Cl2 → Clδ+ – AlCl3δ– (1)	1
(iii)

correct dipole / Cl+ (1)
curly arrow from benzene ring to Cl+ / Clδ+ (1)
intermediate (1)
curly arrow from H to regenerate benzene ring in intermediate (1)
H+ as other product (1)	4
(iv)	electrophilic substitution (1)
with electrophilic spelt correctly	1
(b)	In benzene, π electrons are delocalised/spread out (1)
In alkenes, π electrons are concentrated between 2 carbons (1)
Electrophiles attracted more to greater electron density in alkenes (1)	3
[10]

 4.	bonding in benzene
overlap of p-orbitals / π bonds/electrons (or labelled) (1)

 	above and below the ring (or shown in a diagram) (1)
electrons are delocalised (or labelled) (1)
C–C bonds are: same length/strength / in between single and
double / σ-bonded AW (1)
	greater reactivity of phenol
(the ring is activated because …)
lone pair from O is delocalised into the ring (1)
so electron density (of the ring) is increased (1)
so electrophiles are more attracted (to the ring) / dipole in
electrophile more easily induced (1)
(NOT just more easily “attacked” or “susceptible”)
	Quality of written communication mark for at least two
complete sentences in which the meaning is clear with correct
spelling, punctuation and grammar (1)	8
[8]

5.	(a)	(i)	NaOH / Na (1)	1
(ii)	C6H5OH + NaOH → C6H5O–Na+ + H2O /
C6H5OH + Na → C6H5O–Na+ + ½H2 (1)	1
(b)	(i)
 (1)	1
allow a dipole on just one C=O bond
(ii)
 (1)(1)	2
(iii)	lone/electron pair from oxygen is delocalised into the
ring /interacts with π-electrons (1)
	increases π-electron density / negative charge
(around the ring) (1)
	attracts electrophiles more (1)	3
(c)	Mr salicylic acid = 138 (1)
	moles (in 1:1 reaction) = 3500 x 106/138 = 2.536 x 107 (1)
	mass of phenol needed = 2.536 × 107 × 94 = 2384 tonnes (1)
	allowing for 45% yield = 2384 × 100/45 = 5298/5300 (tonnes) (1)	4
allow 5297.5–5300
allow ecf throughout
[12]
 
6.	(a)	Correct structure of 3-nitrophenol or any multiple nitrated phenol (1)	1
(b)	Mr phenol (C6H6O) = 94.0 (1)
	Mr 4-nitrophenol (C6H5NO3) = 139.0 (1)
	expected mass/moles of nitrophenol from 100 g =
148 g/1.06 mol (or ecf from wrong Mrs) (1)
	at 27% yield gives 40 / 39.9 (g) (or ecf) (1)	4
last mark is for 0.27 × expected mass to 2 or 3 sf

(c)	conditions for nitration of benzene:
HNO3 is concentrated (1)
	conc H2SO4 is present (1)
	heating or stated temp above 50°C (1)	3
	explanation for greater reactivity of phenol
lone pair from O atom is delocalised into the ring (1)
	greater (π) electron density around the ring (1)
	(the benzene ring in phenol) is activated (1)
	attracts electrophiles/+NO2 more / makes it more
susceptible to electrophiles AW (1)	4
	quality of Written Communication mark for at least two legible
sentences with correct spelling, punctuation and grammar	1
[13]

7.
		2
allow bromination in any positions on the ring
[2]