11 mark
Which organic functional group could have produced the infrared spectrum below?
An aldehyde
An alcohol
A carboxylic acid
A ketone
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3.6 Organic Analysis
21 mark
Which of the following cannot be obtained from an infrared spectrum?
The molecular mass
The presence of C=O bonds
The presence of O-H bonds
The identity of a compound through comparison with other spectra
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31 mark
What chemical reagent(s) could be used to determine that bromide ions were present in a solution?
Silver nitrate (aq)
Barium chloride (aq)
Silver nitrate (aq) + dilute ammonia (aq)
Silver nitrate (aq) + concentrated ammonia (aq)
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41 mark
2-methylpropan-1-ol is distilled in the presence of acidified potassium dichromate(VI). The distillate is then warmed with Fehling’s solution and a brick red precipitate forms.
Which functional group is present in the distillate?
Ketone
Aldehyde
Carboxylic acid
Tertiary alcohol
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51 mark
What is meant by the term ‘fingerprint region’ on an infrared spectrum?
|
|
Between 500 - 1500 cm-1 |
Absorption for C-O bond |
Measures intensity of absorption |
Used for comparison against known compounds |
|
A |
⨯ |
✓ |
⨯ |
⨯ |
|
B |
✓ |
⨯ |
⨯ |
✓ |
|
C |
⨯ |
⨯ |
✓ |
⨯ |
|
D |
✓ |
✓ |
⨯ |
⨯ |
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61 mark
In mass spectrometry, what is the molecular ion peak (M+) of ethanoic acid?
[CH3COOH]+, m/z = 60
[CH3COOH], m/z = 60
[CH3COOH]+, m/z = 59
[CH3COOH], m/z = 61
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71 mark
What organic functional group could have produced this infrared spectrum?
Alcohol
Carboxylic acid
Aldehyde
Carbonyl
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81 mark
What would be observed if aqueous magnesium sulfate was reacted with acidified barium chloride?
Cream precipitate
Yellow precipitate + effervescence
White precipitate
Colour change orange to green
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91 mark
Using the mass spectrum below, what is the molecular ion peak of 2-methylbutane?
27
43
57
72
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11 mark
Mixture F is produced upon refluxing compound G with aqueous sodium hydroxide.
Upon distillation of F with acidified potassium dichromate(VI), propanone is produced. Mixing G with aqueous silver nitrate and dilute nitric acid gives a cream precipitate.
What is the identity of compound G?
CH3CHICH3
CH3CHBrCH3
CH3CH2CH2I
CH3CH2CH2Br
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21 mark
When the apparatus below was used with compound E, a brick-red precipitate formed in the right-hand tube.
Which compound could be E?
|
|
CH3OH |
CH3CH2CH2OH |
CH3CH(OH)CH3 |
HCOOCH2CH2CH3 |
|
A |
⨯ |
✓ |
⨯ |
✓ |
|
B |
✓ |
✓ |
⨯ |
⨯ |
|
C |
⨯ |
⨯ |
✓ |
⨯ |
|
D |
⨯ |
⨯ |
⨯ |
✓ |
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31 mark
An alcohol can be prepared by hydrolysing the halogenoalkane C4H7CHClCH3 with aqueous sodium hydroxide.
The infrared spectrum for C4H7CHClCH3 is shown in with the C–Cl bond absorption is labelled.
How will the infra-red spectroscopy change as a result of the above reaction?
|
|
Appearance of peak at 3230 - 3550 cm−1 |
Appearance of peak at 2500 - 3000 cm−1 |
Disappearance of peak at 500 - 800 cm−1 |
Appearance of peak at 1680 - 1750 cm−1 |
|
A |
⨯ |
✓ |
✓ |
⨯ |
|
B |
✓ |
⨯ |
⨯ |
⨯ |
|
C |
✓ |
⨯ |
✓ |
⨯ |
|
D |
⨯ |
⨯ |
✓ |
✓ |
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41 mark
The mass spectra of three compounds A, B and C are shown below.
Which of the following features of the three compounds A, B and C shows the molecular formula is C4H10O?
All show a molecular ion peak at 74
All show a molecular ion peak at 15
All show a molecular ion peak at 73
All show a molecular ion peak at 44
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51 mark
The infrared spectrum of an unknown compound is shown below.
Which compound could have produced the infrared spectrum?
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61 mark
A compound XFn is a fluoride of another halogen, X, and it is known that n > 1. The highest mass peak in the spectrum of XFn is the parent ion and has a single peak at m/z = 222.
Which of the following statements is incorrect?
n = 5
X electronegativity value＜ F
The compound could contain bromine
The compound is a fluoride of iodine
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71 mark
A sample is analysed by mass spectrometry and infrared spectroscopy. The following incomplete data is obtained.
|
Mass Spectrometry |
Infrared Spectroscopy |
|
Molecular ion peak at m/z = 128 |
Sharp peak at 1720 cm-1 |
|
Fragment ion peak at m/z = 15 |
No broad peak around 3200 cm-1 |
Which of the following compounds could be present in the sample?
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81 mark
Which of the following isomeric alcohols, with molecular formula C5H12O, cannot be oxidised to a carboxylic acid?
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91 mark
In mass spectrometry, which compound forms a molecular ion with a different precise molecular mass from the other three compounds?
Cyclopentanol
Dimethylbutane
Pentanone
Methylbutanal
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101 mark
This question is about the reaction between cyclopropanone and an excess of methanol which forms a hemiketal compound as shown below.
Which infra-red absorption would the products not produce?
1700 cm-1
2900 cm-1
1200 cm-1
3300 cm-1
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11 mark
Which of the following compounds would form an orange-red precipitate when heated with Fehling’s solution?
CH3CHO
CH3CH2CH2CH2COOH
CH3CH2CH2Cl
CH3CH2COCH3
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21 mark
Which alcohol is not likely to have a fragment ion at m/z at 43 in its mass spectrum?
CH3CH2CH2CH2OH
CH3CH(OH)CH2CH2CH3
(CH3)2CHCH2OH
CH3CH2CH(OH)CH3
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31 mark
Butanal, CH3CH2CH2CHO, and butanone, CH3CH2COCH3, are carbonyl compounds.
When these compounds are compared using analytical methods, which of the following statements is not correct?
The compounds produce different patterns in the fingerprint region of the IR spectrum
The carbonyl groups absorb at frequencies in the same region of the IR spectrum
The compounds have molecular ion peaks at different mass to charge ratios in a mass spectrum
The compounds produce different fragmentation patterns in a mass spectrum
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41 mark
Bromine exists as two isotopes 79Br and 81Br, which are found in almost equal abundance.
Which of the following statements is correct?
79Br is more reactive than 81Br
The mass spectrum of C3H7Br has two molecular ion peaks at 122 and 124
The atomic radius of 79Br is less than the atomic radius of 81Br
The first ionisation energy of 79Br is less than the first ionisation energy of 81Br
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51 mark
Which compound is shown in the infrared spectrum below?
Butanoic acid
Butanal
But-1-ene
Butan-1-ol
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61 mark
Which pair of compounds would you expect to both have a singly charged peak at m/z = 29 in the mass spectrum?
propanal and propanone
propan-1-ol and propanal
propan-2-ol and propanal
propanone and propan-2-ol
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71 mark
Which compound below does not contain the functional group shown by the infrared spectrum?
carboxylic acid
alcohol
ketone
aldehyde
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81 mark
Which of the ketones listed would not be expected to have a peak in its mass spectrum at m/z = 57?
CH3CH2CH2COCH2CH3
CH3CH2COCH2CH3
(CH3)2CHCOCH3
CH3CH2COCH3
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91 mark
Crotonaldehyde, CH3CH=CHCHO, occurs in soybean oils and can be formed from its alcohol.
Other than the alcohol of crotonaldehyde, what reagents and experimental conditions are needed for producing crotonaldehyde?
|
|
Reflux |
Distillation |
K2Cr2O7 |
K2Cr2O7/H+ |
|
A |
✓ |
⨯ |
✓ |
⨯ |
|
B |
✓ |
⨯ |
⨯ |
✓ |
|
C |
⨯ |
✓ |
⨯ |
✓ |
|
D |
✓ |
✓ |
⨯ |
✓ |
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101 mark
Calcium iodide is reacted with silver nitrate and a yellow coloured precipitate is produced.
Which pair of responses helps to confirm the identity of the anion?
|
|
Solubility in dilute ammonia |
Solubility in concentrated ammonia |
|
A |
insoluble |
insoluble |
|
B |
insoluble |
soluble |
|
C |
soluble |
insoluble |
|
D |
soluble |
soluble |
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