4.3.2 EXAM QUESTIONS mark scheme

1.	(a)	5 (1)	1
(b)	2:2:2:3:3 (1)
any order but not multiples
		1 
(c)	 (1)	1
(d)	CH3CH2 or C2H5 or ethyl (1)
d4.13 (quartet) : CH2 peak split by CH3 / next to CH3 (1)
d1.26 (triplet) : CH3 peak split by CH2 / next to CH2 (1)	3

(e)	CH2CH2 (1)	1 
(f)	(2)
allow (1) for CH3COCH2OCOCH2CH3
or CH3COOCH2COCH2CH3
Must be C7H12O3
		2
[9]

2.	(a)	C=O (1)	1
or “carbonyl” 
(b)	(i)	Cl has (2) isotopes (1)
Allow 35Cl and 37Cl without word isotope – but must be correct isotopes
must have 3 different elements, i.e. not C3H7+ but allow balanced equation including C3H7+ for the equation mark
(ii)	Fragmentation:  (1)
must be an ion (*)
Equation: C4H7ClO+· ®  + C2H4Cl· (1)	3
(*) allow C2H3O+ or any form of it (i.e. CH2CHO+ or CH2COH+) in equation, be generous with position of + or ·
if fragment ion completely wrong (not m/z = 43) no further marks
(c)	(i)	CDCl3 or CCl4 (1) or D2O, C6D6
(ii)	Si(CH3)4 (1) or SiC4H12	2
(d)	
	Peak 1	Peak 2	Peak 	
Integration value	3	3	1	
Splitting pattern	doublet	singlet	quartet	
Number of adjacent, non-equivalent protons	1	0	3	
	(1)	1 
(e)	 (1)	1
or CH3COCHClCH3
	
[8]
3.	(a)	 (1)	1
(c)	CH3CH2COOCH2CH3+· ® CH3CH2C+=O (1)+ CH3CH2O·
equation (1)
		2
(d)	CH3CH2CH2COOCH3 or (CH3)2CHCOOCH3 (1)
Allow C3H7COOCH3
		1
[4]
4.	(a)	(i)	(CH3)2CHCOCH3+·  ®  (CH3)2CHCO+ + H3
        (1) 	(1)	(1)
(ii)	Structure 1	Structure 2
   CH3CO+	(CH3)2CH+
(1) 		(1)	5
(b)	two isotopes  (1)
C3H735Cl = 78    C3H737Cl = 80  (1)
relative abundances  35Cl:37Cl = 3:1  (1)	3
[8]
5.	(a)	2-chloropropanoic acid (1)	1
(b)	d1.72 Doublet \ next to CH (1)
d4.44 Quartet \ next to CH3 (1)	2 
(c)	Two triplets (1)	1
[4]
6.	(a)	R: O-H (alcohols) (1)
		S: C=O or carbonyl (1)
		2 
(b)	aldehyde (1)	-CHO or RCHO (1)
		1
(c)	(i)	Reason 1: TMS inert or non-toxic or volatile / easily removed
Reason 2: single (intense) peak
	 peak of 12 protons
	 has 12 equivalent protons
	 all protons in same environment
OR
	 peak / signal upfield of others
	 highly shielded
	 more shielded
	 peak away from others or d = 0 or low
not solvent, not cheap
any 2 reasons × (1)
(ii)	Solvent: CDCl3 or CCl4 (NOT D2O)
Reason: proton free (1)
	 allow no hydrogens (atoms)
NOT H+ / hydrogen ions
		4 
(d)	(i)	 (1)
(ii)	–OH (1)
(iii)	–CH2–CH2– (1)	3
(e)	 (1)	1
[11]
7.	(a)	A is RCOOR¢ (1)
R + R¢ = 102 – 44 = 58 (1) º C4H10
\C5H10O2 (1)	3
(b)	2 : 2 : 3 : 3 (1)	1 
(c)	Two CH2CH3 groups present (1)	1
(d)	CCCOOCC (1)	1 
(e)	
Chemical shift, d/ppm	1.09	1.33	2.32	4.13	
Label of group	a (1)	d (1)	b (1)	c (1)	
		4
[10]

 8.	(a)	(CH3)4 Si or tetramethylsilane  (1)	1
(b)	4  (1)	1
(c)	2 : 1 : 6 : 3  (1)	1
(d)	–CH2CH3  (1)
CH3 splits CH2 to form a quartet  (1)
CH2 splits CH3 to form a triplet  (1)	3
(e)	two equivalent CH3 groups  (1)	1
(f)		1
[8]

9.		(i)	CH3COOCH2CH3 or CH3COOC2H5 (1)
(ii)	3 (1)
(iii)	3 + 4 or triplet + quartet (1)	3
 
 [3]

10.	(a)	same molecular formula / same number of each type of atom (1)
	different arrangements of atoms (in the molecule)  (1)
(not just same structural formula)	2 
(b)	(i)	

	(1)	(1)	2
 
(ii)	43:	CH3CH2CH2+/ CH3C+HCH3 / C3H7+ (1)
29:	CH3CH2+ / C2H5+  (1)
15:	CH3+  (1)
(2 max if +ve sign omitted or –ve) (+ can be anywhere)	3
 
(iii)	Isomer 1 (dependent on candidate’s order)  (1)
Isomer 2 could not (easily) give peak at 29 / C2H5+  (1)	2
(c)	(i)	      (1)
      (1)	2 
(ii)	ester (1)
carboxylic acid  (1)
	names must be appropriate way round relative to (i)
these marks dependent on correct answers in (i)	2
[13]

11.	(a)	A	B
CH3COOH (1)	HCOOCH3
	or HOCH2(1)	2
(b)	C	D
CH3CH2CH2OH	CH3CH2–O–CH3 (1)
or CH3CH(OH)CH3 (1)		2
(c)	E	F
			2
(d)	G	H
CH3CH2CHO (1)	CH3COCH3 (1)	2 
(e)	I	J
		2 
 [10]

12.		(i)      Equation 	CH3COCH3 + 2[H] ® CH3CH(OH)CH3 (1)
Reducing agent 	NaBH4 (1) 
(ii)	

		6
[6]

13.	A	1715 cm–1	C=O group (1)
B	3350 cm–1	O–H group	alcohol (1)
A 
	two environments or two kinds of proton (1)
CH3CH2 adjacent or coupled (1)
ratio 2:3 or 4:6 (1) symmetric (1) 
[CH3CH2COCH2CH3]+. ® CH3CH2CO+ + CH3CH2. (1)
m/z = 86 (1)	(1)
or Mr for A

CH3CH2HCH2CH3 (1) and CH3HCH2CH2CH3 (1)
	both secondary (1)
hydration gives B and  
about 50% of each (1)
A ® B reduction
B ® C dehydration or elimination (1)
C is an alkene (1) cis/trans isomers (1)
D is a racemate (1) or optical isomers	any 20
[20]

14.	(a)	X (O–H) (alcohols)   penalise acid or missing “alcohol”	1
Y C=O   allow carbonyl	1
	4
NOT acid
(b)	

		3
Allow conseq dibromocompounds following incorrect unbranched alkenes 
NOT allow dibromocompound consequent on a duplicate alkene
NOT allow monobromocompounds if HBr added

	6:3:1 either next to correct structure or to none	1
	Allow a mark for identifying correct dibromocompound with three peaks
even if integration ratio is wrong	1
	if 6:3:1 missing or wrong, no marks for splitting	1
	Only award a mark for splitting if it is clear which integration number it
refers to	1
	6 singlet or drawn	1
	3 doublet or drawn	1
	1 quartet/quadruplet or drawn	1
[16]

 20.	(a)	(i)	3 peaks or shown in a list	1
m/z = 126, 128 and 130 (56 +70/72/74) (all 3 scores 2)	2
(if 56 wrong allow (x + 70/72/74) for1(x cannot be zero)
(any two scores 1) 
(ii)		3

(1)	(1)	(1)

(b)		optical	1
equal mixture of enantiomers	1
(optically) inactive or effects cancel	1
plane polarised light	use stereospecific reagent (QoL)	1
rotated in opposite/different 
directions (QoL)	reacts with one isomer only	1 
		4 max
 
(c)	(i)	2 peaks (if 4 peaks allow splitting only)	1
ratio 6:2 or 3:1	1
doublet (6 or 3)	1
quartet (2 or 1)	1 
(ii)	S	
		1
T	
	1
[16]

16.	(a)		1
	1
NB	The bonds shown in the structure must be correct
	Isomerism:     Geometric or cis-trans	1
If written answer is correct, ignore incorrect labelling of structures.
If no written answer, allow correctly labelled structures.
	Both COOH groups must be on the same side/ close together/ cis .	1
	No rotation about C=C axis	1
	Structure
	1 
(b)	Br2 / HBr / H2SO4 / H+ / Br+ / NO2+ (Mark M1)	4

NB If electrophile H+ / Br+ / NO2+ allow M1, M2 and M4
If the acid is incorrect, M2 and M3 can still be scored
Allow M4 consequentially if repeat error from part (a)

(c)	e.g. 2NaOH + HO2CCHCHCO2H ® NaO2CCHCHCO2Na + 2H2O
	Both H replaced	1
Balanced for atoms and charges	1
NB	Allow ionic equations and 2NaOH + C4H4O4 ®
	C4H2O4Na2+ 2H2O
	Allow one if structure incorrect but molecular formula
	correct
	Allow one for a correct equation showing one H replaced 
(d)	M1	Two peaks	1
M2	No splitting or singlets	1
M3	(Two) non-equivalent protons or two proton environments	1
M4	No adjacent protons	1
M5	Same area under the two peaks or same relative intensity	1
		Max 3
NB	Doublet could score M1 and M3 or M5 (Max 2)
	More than two peaks CE = 0
	Apply the “list principle” to incorrect answers if more
	than 3 given
[15]

17.	(a) X is methyl propanoate	1
	(b) Spectrum 2	1
if thinks Spectrum 1 = X can only score for structure of Y
	Y is CH3COOCH2CH3	1
The two marks for explanation are awarded for discussing one or more of the	2
four peaks (not those for the CH3 of the ethyl groups)
for stated d values the integration or the splitting should be related to the
structure: e.g. structure of X shows that
	at d 3.7 – 4.1 (1) spectrum of X should have integration 3 / singlet (1)
or
	at d 2.1 – 2.6 (1) spectrum of X should have integration 2 / quartet (1)
	Spectrum 2 has these
[OR Spectrum 1 has
	at 3.7 – 4.1 (1) quartet / integration 2 (1) so not X
	at 2.1 – 2.6 (1) singlet / integration 3 (1) so not X]
[5]
 
18.	(a)	K2Cr2O7/H2SO4 reuced by
	CH3CH2CH2CH2OH (1)
	oxidised to	CH3(CH2)2CHO (1)
and	CH3(CH2)2COOH (1)
CH3CH2CH2CHO (1)
	oxidised to	CH3(CH2)2COOH (1)
Equation:	Cr2O72– + 14H+ + 6e– ® 2Cr3+ + 7H2O (1)	6
Note: Deduct one if all three compounds given as reducing agents.
(b)	Tollens’ reduced by
	CH3CH2CH2CHO (1)
	oxidised to	CH3(CH2)2COOH (1)
Equation	[Ag(NH3)2]+ + e– ® Ag + 2NH3 (1)	3 
(c)	CH3CH2CH2CH2OH (1)
	Product	CH3CH2CH2CH2OOCCH3 (1)
(CH3)3COH
	Product	(CH3)3COOCCH3 (1)	4
 
(d)	CH3CH2CH2OH has five peaks (1)
(CH3)3COH has two peaks (1)	2
[15]

19.	(a)	3 Ketones:

	3: 2: 2: 3  (1)	6: 1: 3  (1)	6: 4 or 3: 2 (1)
6 
(b)	4 aldehydes:
	7
 
(c)	Reagents are oxidizing agents  (1)
Aldehydes can be (easily) oxidized  (1)
Ketones are not (easily) oxidized  (1)	3
[16]

20.	Part (a) for each section:
	A totally wrong reagent scores zero
An incomplete reagent such as silver nitrate for Tollens, loses the reagent mark, but can get both observation marks.
A wrong reagent such as [Ag(NH3)2]2+ or bromide water loses the reagent mark and the next mark “gained”, i.e. can only score 1/3 if both observations correct
	If two test given and results given correctly for both compounds in both tests then full marks
If one test on A and a different test on B with only these results given
	if both results correct then score 2/3
	if either result wrong then score 1/3
if either test would not work as a distinction, then score 0/3
	If the candidate says A = ketone (or C = benzene), lose this mark.
	If the candidate omits the letters when referring to the pair of compounds,
e.g. says alkene decolourises / alkane no reaction penalise one mark only.

(a)	(i)	penalise observations which just say colour change occurs or only state starting colour
Tollens	[1]	Fehlings / Benedicts	[1]	Brady’s or 2,4-dnph	[1]	sodium	[1]	
No reaction A	[1]	no reaction A	[1]	no reaction A	[1]	bubbles or hydrogen A	[1]	
silver mirror or grey or ppt B	[1]	red or ppt B	[1]	(Yellow / orange) Xtals or ppt	[1]	no reaction B	[1]	
(not silver solution)	[1]	not red solution	[1]	not yellow / orange solution	[1]			

Carboxylic acid / H2SO4	[1]	Schiff’s	[1]	iodoform or I2 / NaOH	[1]	PCl5	[1]	
(sweet) smell A	[1]	no reaction A	[1]	yellow (ppt) A	[1]	(misty) fumes A	[1]	
no reaction B	[1]	goes pink B	[1]	no reaction B	[1]	no reaction B	[1]	
 (ii)
Bromine (water)	[1]	KMnO4	[1]	KMnO4 / H2SO4	[1]		[1]	
no reaction C	[1]	no reaction C	[1]	no reaction C	[1]		[1]	
decolourised D	[1]	goes brown D	[1]	goes colourless D	[1]		[1]	
not clear not discolour (is)ed								
(iii)	not just smell for E
an identified (hydrogen) carbonate	[1]	correct metal	[1]	UI or stated indicator	[1]	PCl5	[1]	
no reaction e	[1]	no reaction E	[1]	no change E	[1]	(misty) fumes E	[1]	
bubbles or CO2 F	[1]	bubbles or H2 F	[1]	red or correct colour F	[1]	no reaction F	[1]	
		note MAX 8 
(b)	F has absorption at 2500 - 3000 cm–1 (due to COOH) (1)
N.B. Qu asks “How fingerprinting is used” i.e. no marks for simply
stating fingerprint region unique.
Compare with (spectrum of) known compound or database (1)
(exact) match	3

(c)	major peak [CH3CO]+ (1)
m / z	43 (1)
CH3COOCH3+. ® CH3CO+ + OCH3. 
(1 for molecular ion)	(1 for correct other fragment)
	Alternative:
	major peak [CH3]+ (1)
m /z	15 (1)
CH3COOCH3+. ® CH3+ + CH3COO. or COOCH3. or C2H3O2. or C3H6O2+.
(1)	(1 for radical)
	If major peak wrong but possible e.g. CH3OO+ m/z = 59
no marks so far, but can score up to 2 for
CH3COOCH3+. ® CH3+ + CH3COO+ or +COOCH3 + CH3
1 for correct other fragment]
		4
[15]

21.	(a)	X contains >C=O (1)
if X and Y reversed lose this mark but allow remaining max 6/7
\ X is CH3CH2COOH (1)
\ Y is CH3CH2CH2OH (1)
\ A is  (1)

Conc H2SO4 : catalyst (1)	7
(b)		4

(c)		3.1 – 3.9 (1)
	2.1 – 2.6 (1)
a: quartet (1)  3 adjacent H (1)
b: triplet (1)  2 adjacent H (1)	6 
(d)	3269 cm–1 \OH  alcohol (1)
\ G is  (1)	2
	Notes
(a)	first mark for C=O stated or shown in X
Ignore wrong names
	Y CH3CH2CH2OH
allow C3H7 in A if Y correct or vice versa
Allow (1) for A if correct conseq to qrong X and Y
	other oxidising agents: acidified KMnO4; Tollens; Fehlings
	other reducing agents: LiAlH4; Na/ethanol; NiH2; Zn or Sn or Fe/HCl
(b)	give (1) for carboxylic acid stated or COOH shown in each suggestion
(1) for correct E
any 2 out of 3 for B, C or D
allow C3H7 for either the B or D shown on the mark schme
i.e. a correct structure labelled B, C or D or E will gain 2.
(c)	protons a – quartet must be correct to score 3 adjacent H mark. Same for b
(d)	allow (1) for any OH (alcohol) shown correctly in any structure – ignore extra functional groups. Structure must be completely correct to gain second mark
[19]
	Organic points
(1)	Curly arrows: must show movement of a pair of electrons,
i.e. from bond to atom or from lp to atom / space
e.g.

(2)	Structures
penalise sticks (i.e. ) once per paper

Penalise once per paper
	allow CH3– or –CH3 or  or CH3
    or   H3C–

22.		A gives three peaks (1)
B gives one peak (1)
Allow one for “A has more peaks than B” when no number of
peaks is given
		2
[2]
23.	A:	4 peaks  or  4 different environments  (1)
1 : 2 : 2 : 3  (1)  OH singlet  (1)  CH3  singlet  (1)
2 triplets  (1) CH2CH2 coupled  (1)
B:	4 peaks  or  4 different environments  (1)
1 : 2 : 2 : 3  (1)  OH singlet  (1)  OCH2O singlet  (1)
quartet + triplet  (1)  CH2CH3 coupled  (1)
C:	2 peaks or 2 different environments  (1)
2 : 6  or  1 : 3  (1)  CH3 groups equivalent  (1)
2 singlets  (1)  no coupling  (1)
[max 15]

24.		(i)	2-chloro(-2-)methylpropane / (2)methyl 2 chloropropane (1)	1
(ii)	compound D (1)
	all same type of protons / hydrogen are all in same (chemical)
environment / equivalent as they are all CH3 (1)	2
(iii)	compound C (1)
ratio = 6:2:1 (1)
	2 CH3 groups have 6 equivalent protons, CH2 has 2 protons,
CH 1 proton (1)	3
must say same type of proton / H
penalise first omission of ‘same type’ 
(iv)	appropriate unambiguous formula for either but-1-ene or but-2-ene (1)
appropriate unambiguous formula for the remaining structural isomer
allow 1 mark if candidate draws cis and trans but-2-ene (1)	2 
(v)	unambiguous structure for 2-methylpropan-1-ol – may be
from mechanism (1)
	curly arrow / attack by OH–         curly arrow from lone pair or
charge only (1)
do not allow if Na -OH 
	curly arrow from bond to Cl / dipole shown on
C-Cl bond / intermediate showing 3 full and 2 partial bonds to C (1)
	loss of Cl– 	NaCl or Na+:Cl– (1)
– not allowed		4
	if SN1 mechanism given: 
first mark as above - independent
second mark for correct carbocation formed including curly
arrow from C to Cl or CS+ –ClS –
	third mark for hydroxide attack as above
final mark not available (wrong mechanism)
penalise missing proton once only
[10]

 

25.	(a)	A 	C6H14 (1) 		Ratio 12:2 or 6:1 (1)
B/C	C=O (1)	C5H10O (1)
CH3CH2CH2 CH3 (1) 	ratio 6:4 or 3:2 (1)
(1)	ratio 9:1	9 
(b)	Tollens (1) 	silver mirror with aldehyde (1)
		no reaction with ketone (1)
(or Fehlings  red ppt with aldehyde, no reaction with ketone)
Fingerprint region (1)
Exact match with standard (1)	5
 [14]

26.	(a)	Region 1500–400 cm –1 (1)
unique for each compound (1)
compare spectrum with that of known compound (1)
exact match (1)	4
(b)	C5 esters
	 (2)
	 (2)
	 (2)
	T (alcohol) is CH3CH(OH)CH3 (2)
(3 peaks)
	U (acid) is CH3COOH (2)
(2 peaks)
T absorption at 3250 cm–1 confirms OH (alcohol) (1)
U absorption at 2900cm–1 confirms OH (acid) or at 1700 cm–1 confirms C=O (1)	max 11
[15]

27.	(a)	

	A = butanal
	B = methylpropanal
	C = butanone
	D = ethyl ethanoate  (1)
	Ignore numbers in names unless they make them incorrect
spellings must be correct
accept alternative trivial names correctly spelled	8
(b)	ethanol / correct formula  (1)
	ethanoic acid / ethanoyl chloride / ethanoic anhydride / correct formula  (1)
	temperature less than 100 °C / reflux heat / concentrated sulphuric acid  (1)
dilute sulphuric acid / acid conditions / H+
(this mark dependent on sensible answers for first two marks)
	for ethanoyl chloride, room temperature / dry / anhydrous
	for ethanoic anhydride, heat / up to 100 °C	3
 
(c)	 (1)
	butanoic acid	methylpropanoic acid  (1)	2

(d)	heat with Fehling’s solution / ammoniacal silver nitrate / Tollen’s reagent /
other suitable oxidising system eg acidified dichromate / Schiff’s reagent
	B gives red, green or brown (precipitate) / silver (mirror) or black/grey  (1)
precipitate / other, dependent on reagent
	C shows no change  (1)
	B and C can be referred to as ‘aldehyde’ and ‘ketone’ only if names correct 
in (a) or if there is some other valid identification	3
 
(e)	(i)	B
	two methyl groups / 6 Hs in identical chemical environments or  (1)
2 Hs in unique environments	2
(ii)	A
	four different chemical environments (for protons)  (1)
in (i) and (ii), second mark is dependent on first mark	2
(iii)	same number of hydrocarbon groups with same number of protons in each	1
 
 [21]