TOPIC 20 HW MS

1.   (a)     If 2 stage test for one compound, award no marks for that compound, eg no mark for ROH or RX to alkene then Br2 test. If reagent is wrong or missing, no mark for that test; if wrong but close/incomplete, lose reagent mark but can award for correct observation. In each test, penalise each example of wrong chemistry, eg AgClr2
propan-1-ol
acidifiedpotassiumdichromate
sodium
Named acid + conc H2SO4
named acyl chloride
PCl5
M1
1
(orange) turns green
effervescence
Sweet smell
Sweet smell /misty fumes
Misty fumes
M2
1
	   propanal
add Tollens or Fehlings / Benedicts
acidifiedpotassiumdichromate
Bradys or 2,4-dnph
if dichromate used for alcohol cannot be used for aldehyde
M3
1
Tollens: silver mirror or Fehlings/ Benedicts: red ppt
(orange) turns green
Yellow or orange ppt
M4
1
	   propanoic acid
Named carbonate/ hydrogencarbonate
water and UI (paper)
Named alcohol + conc H2SO4
sodium or magnesium
PCl5
if sodium used for alcohol cannot be used for acid
M5
1
effervescence
orange/red
Sweet smell
effervescence
Misty fumes
if PCl5 used for alcohol cannot be used for acid
M6
1
1-chloro propane
NaOH then acidified AgNO3
AgNO3
If acidification missed after NaOH,no mark here but allow mark for observation
M7
1
white ppt
white ppt
M8
1

(b)      oxidation (of alcohol by oxygen in air)
M1
1
absorption at 1680 -1750 (due to C=O)
Must refer to the spectrum
M2
1
comparison of polarity of molecules or correct imf statement:propanone is less polar OR propan-2-ol is more polarOR propanone has dipole-dipole forcesOR propan-2-ol has hydrogen bonding
M3
1
about attraction to stationary phase or solubility in moving phasePropan-2-ol has greater affinity for stationary phase or vice versaOR propanone is more soluble in solvent/moving phase or vice versa
M4
1
[12]

2.      (a)     (i)

allow –CO2–
allow +NH3–
don’t penalize position of + on NH3
1
(ii)     

allow –CO2–
allow NH2–
allow C3H7
1
(iii)     

allow –CO2H
allow +NH3–
don’t penalize position of + on NH3
1

(b)     

1

allow –CO2H
allow NH2–
allow C3H7
allow as zwitterions
if error in peptide link e.g.

if twice, penalise both times
not polymers
if wrong amino acid in both can score Max 1
1
(c)     chromatography or electrophoresis
ignore qualification to chromatography
1
[6]
 
3.      (a)     chromatography (allow GLC TLC GC HPLC)
allow any qualification
1
(b)     5
1
Allow 320(.0) or 322(.0)
1
(c)     Use of excess air/oxygen or high temperature (over 800 °C)
or remove chlorine-containing compounds before incineration
1
(d)     (i)      Si(CH3)4 allow SiC4H12
allow displayed formula and do not penalise sticks
Not TMS
1
(ii)     3
1
[6]

4.      (a)     (i)      
 or RCOCH3;
(or description in words)
(ignore trailing bonds)
1
(ii)     H3C—O or ROCH3;
(allow 1 if both (i) and (ii) give CH3- or H3C– only)
1
(iii)     CH2CH2 or two adjacent methylene groups;
1
(iv)

OR
CH3COCH2CH2OCH3;
1
(b)     (i)      OH in acids or (carboxylic) acid present
(ii)

(c)     
 
reagent	K2Cr2O7 /H+	KMnO4 /H+	
Y	no reaction	no reaction	
Z	orange to green or turns green	purple to colourless
or turns colourless	

5
[9]

5.	(a)    OH alcohols
1
(b)     (i)     2.6

Ignore any group on RHS
Must clearly indicate relevant two H on a C next to C=O
On LHS, penalise H or CH or CH2 or CH3
Ignore missing trailing bonds or attached R groups
1
(ii)     2.2

Ignore all groups on RHS
Must clearly indicate relevant three H on C next to C=O
Ignore missing trailing bonds or attached R group
1
(iii)    1.2

Or in words: two equivalent CH3 groups
Must clearly indicate two equivalent methyl groups.
Penalise attached H
Ignore missing trailing bonds or attached R groups
1
(iv)
1
[5]
 
6.    (a)     (i)      Single / one (intense) peak / signal OR all H or all C in same environment OR 12 equiv H or 4 equiv C
Do not allow non-toxic or inert (both given in Q)
Any 2 from three
Ignore peak at zero
OR
Upfield / to the right of (all) other peaks OR well away from others OR doesn’t interfere with other peaks
Ignore cheap
Ignore non-polar
OR
Low bp OR volatile OR can easily be removed
Ignore mention of solubility
2
(ii)
Allow Si(CH3)4
1

(b)    (i)
Ignore any group joined on other side of CO
Ignore missing trailing bond
Ignore charges
1
(ii)
Ignore any group joined on other side of −O−
Ignore missing trailing bond
Ignore charges as if MS fragment
1
(iii)
Ignore missing trailing bonds
Ignore charges as if MS fragment
1
(iv)  
1

(c)    (i)      Check structure has 6 carbons

Allow (CH3)3CCOOCH3 or (CH3)3CCO2CH3
1
	
Allow CH3COOC(CH3)3 or CH3CO2C(CH3)3
1
(ii)     Check structure has 6 carbons

Allow (CH3)2CHCH(CH3)COOH or (CH3)2CHCH(CH3)CO2H
Penalise C3H7
1
(iii)    Check structure has 6 carbons

OR
 
Allow

1
[11]

7.       (a)     A
	
allow CH3COCH3
1
          B       
must show C=C
Penalise sticks once per pair
1
(b)     C       CH3CH2CH2CH2CH3
1
D       
NOT cyclopentane which is only C5H10
Penalise sticks once per pair
1
(c)     E       CH3CH2COOCH3
Allow C2H5CO2CH3
1
F       CH3COOCH2CH3
Allow CH3CO2CH2CH3 or CH3CO2C2H5
Penalise sticks once per pair
1
(d)     G       
         allow C3H7                           allow C3H7                                allow C2H5
 
not C5H11 nor C4H9
Penalise sticks once per pair
1
H       
allow C2H5
1

(e)     I         
allow C2H5
1
J        
NOT C3H7
Penalise sticks once per pair
1
[10]
 
8.    (a)     (i)      

not allow C3H7
allow C2H5 bonded to C either way round
1
(ii)     elimination
allow base – elimination
but penalise any other qualification
1
(iii)     Z-pent-2-ene or cis-pent-2-ene               either Z or cis is necessary
(allow Z-2-pentene or cis-2-pentene)
with or without brackets around Z
with or without hyphens
1
(b)     (i)      C
1
(ii)     A
1
(iii)     B
1
(iv)    D
1
(c)     

allow C2H5 bonded via C or H
must have both trailing bonds
ignore brackets or n
1
addition or radical or step or chain growth
QOL not additional
1

(d)     (i)

Allow SN1, i.e M2 first then attack of NH3 on carbocation.
Allow C2H5 in M3 bonded either way
Allow with or without NH3 to remove H+ in M4, but lose mark if Br– used.
ignore δ+ or δ– unless wrong
+ on central C instead of δ + loses M2
4
(ii)     excess NH3
ignore reflux
allow conc ammonia in sealed tube
1
(iii)

Allow C2H5 bonded either way
1
(e)     (i)

1
(ii)

NOT (C2H5)2NCH3 which is tertiary with 3 peaks but its spectrum has no doublet.
1
[17]

 

9.	D
[1]
10.		B
[1]
11.		D
[1]
12.		C
[1]