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Year 13 Chemistry Assignment No. 16
Organic #2
Identification reactions
(62 marks)
1.
(a)
(b)
(c)
(d)
(e)
(f)
(g)
(h)
2.
Draw and name the alcohol isomers of C4H10O
Name the isomer that is resistant to oxidation.
Classify this alcohol as primary, secondary or tertiary.
Depending on reaction conditions, oxidation of butan-1-ol can give two different organic products.
Name the functional group present in each of these products.
Explain how you could distinguish between these two products.
Name the reagents you would use and say what you would observe.
What reagent would be use to convert butan-1-ol to 1-chlorobutane?
Treatment of 1-chlorobutane with alcoholic potassium hydroxide produces a compound with the
formula C4H8.
(i)
Draw the structure of this C4H8 isomer
(ii)
What type of reaction took place when making this isomer?
(iii)
Name the product formed when this isomer is treated with warm aqueous sulfuric acid.
One of the isomers in part (a) can exist as enantiomers.
(i)
What property must a molecule have for it to exist as enantiomers?
(ii)
Name the isomer that has this property.
(iii)
Draw the two enantiomers of this alcohol showing their three dimensional relationship.
Name this halo alkane and classify it as a 1º, 2º or 3º haloalkane:
CH3CH2C(CH3)2Br
3.
(a)
(b)
(c)
(d)
Starting with 1-Iodopropane give the equation for the preparation of propyl aminobutane.
Name the other reagent.
What type of reaction is this?
Classify the amino alkane product.
4.
Give the equation for the reaction of ethyl amino ethane with sulfuric acid.
5.
Give the equation for the reaction of propanal with acidified potassium permanganate.
6.
Describe one safe simple test you could carry out in a laboratory that would distinguish between
each of the following pairs of compounds. State what you would observe in each case.
(a)
C14H30
and
CH3
C
H
C
H
C
C
H
CH3
H
C
CH3 C
C
H
H
H
(b)
1,2-ethandiol and thin lubricating oil (composed mainly of liquid alkanes)
(c)
Dichloromethane and methylated spirits (mainly ethanol.)
1
7.
A hydrocarbon was found to contain 88.9% carbon and 11.1% hydrogen.
(a)
(b)
Calculate the empirical formula
The molecular mass was found to be 54.0 g mol-1. What was the molecular formula of this
compound?
Give a possible structural formula for this compound
Name the structure you have drawn.
Describe how you could simply in the lab distinguish between this compound and C4H10. Include
any observations you would make.
(c)
(d)
(e)
8.
Draw the structure that would be formed if one molecule of hydrogen bromide reacted with one
molecule of the following substance: CH3
C
H
C
H
H
CH3
C
C
H
C
CH3 C
H
H
C
H
9.
(a)
The compound butan-2-ol can be converted into other organic compounds by substitution,
oxidation and elimination reactions.
Explain the terms in bold above, with reference to the reactions of butan-2-ol.
For each reaction clearly state the:


reagent and conditions needed
structure of any organic product(s) formed.
Balanced chemical equations are not required.
(b)
(6)
Complete the diagram below to show the missing reagents (i), (ii), and (iii) and organic compound
(iv).
CH3CH2COOH
(ii)
(i)
CH3CH2COCl
(iii)
NH3
(iv)
CH3CH2COOCH3
2
(c)
Draw a reaction scheme to show how you could convert a sample of ethene to the ester, ethyl
ethanoate, using only the reagents below.
H2O / H+
10.
MnO4– /H+
Conc. H2SO4
Four unlabelled bottles contain separate samples of methanal, propanone, ethanoic acid and
propan-2-ol.
The reagents below are the only ones that are available:
MnO4– / H+
Tollens’ reagent
Na2CO3
Cr2O72– / H+
Fehling’s solution
Clearly describe a series of chemical tests that could be carried out to distinguish EACH of the
four solutions.
State the steps taken and observations made for each test.
(7)
11.
(a)
CH3 CH2 CH2 C
CH CH O
step Y
CH3 CH2 CH2 C
CH3
(b)
CH C O O H
CH3
Name the type of reaction occurring at step Y.
(1)
Describe a test that would be carried out in the laboratory to identify an aldehyde.
State the reagents and conditions that would be used and the expected observations.
(2)
3
Answers
Year 13 Chemistry Assignment No. 16
Organic #2
Identification reactions
(62 marks)
1
(a)
CH3CH2CH2CH2OH
butan-1-ol
CH3CH2CHOHCH3
butan-2-ol
(CH3)2CHCH2OH
2-methyl propan-1-ol
(CH3)3COH
2-methyl propan-2-ol
(8)
(b)
2-methyl propan-2-ol
(1)
(c)
(d)
Tertiary
Aldehyde and acid
(1)
(2)
(e)
Add an indicator such as bromothymol blue to both
The acid will turn the blue indicator to yellow
The aldehyde will cause no change
or
Warm with Tollen’s reagent
Aldehyde will produce a silver mirror
Acid will cause no change
or
Warm with Fehling’s solution
Aldehyde will produce an orange precipitate
Acid will cause no change
(2)
(f)
PCl5 or SOCl2 or Lucas reagent -- concentrated HCl and anhydrous ZnCl2
(1)
(g)
(i)
(ii)
(iii)
CH3CH2CH=CH2
elimination
butan-2-ol
(1)
(1)
(1)
(h)
(i)
(ii)
(iii)
It must have an asymmetric carbon - has four different groups attached to it.
butan-2-ol
(1)
(1)
CH3 CH2
H
H
C
C
OH
CH3
2.
3.
(a)
(b)
(c)
(d)
HO
CH2 CH3
CH3
(1)
2-methyl-2-bromo butane
Tertiary.
(1)
(1)
CH3CH2CH2I + CH3CH2CH2CH2NH2  CH3CH2CH2NHCH2CH2CH2CH3 + HI
Amino butane
Substitution (nucleophilic)
Secondary amino alkane (amine)
(1)
(1)
(1)
(1)
4
4.
2CH3CH2NHCH2CH3 + H2SO4  (CH3CH2NH2CH2CH3)2+
5.
5CH3CH2CHO + 2MnO4- + 6H+  5CH3CH2COOH + 2Mn2+
6.
(a)
(b)
(c)
3H2O
(1)
(1)
Shake both with bromine solution.
The C14H30 would have no effect while the other one (the unsaturated hydrocarbon) would
decolourise the yellow bromine water.
(1)
Shake with water.
The 1,2-ethandiol will dissolve while the oil will not.
(1)
Warm with acidified potassium dichromate solution.
The ethanol will cause the orange dichromate to turn green while the haloalkane will have no
effect.
(1)
7.
(a)
(b)
SO42-
C
% ratio
88.9
Wt ratio
88.9
mole ratio
88.9 / 12
ie
1
ie
2
 Empirical formula is C2H3
:
:
:
:
:
:
H
11.1
11.1
11.1 / 1
1.5
3
(2)
54.0 / 27 = 2
 Molecular formula is C4H6
(1)
(c)
CH3
C
CH2
CH
(1)
(1)
(d)
But-1-yne
(e)
Shake both with bromine solution.
The C4H10 would have no effect while C4H6 would decolourise the yellow bromine water. (1)
8.
Br
H
H
C
C
H
C
H
CH3
CH3
C
H
C
CH3 C
C
H
H
H
(2)
5
9.
(a)

Substitution reactions involve swapping one atom in the molecule for another. Butan-2-ol
undergoes substitution when reacted with PCl5 /PCl3 / SOCl2 / c. HCl to form 2-chlorobutane,
CH3CHClCH2CH3.
(2)

When butan-2-ol undergoes oxidation it loses hydrogen to form butan-2-one, CH3COCH2CH3,
using either Cr2O72- / H+ or MnO4- / H+ as the reagent.
(2)

Elimination is when atoms or groups of atoms are removed, forming a double bond. When
butan-2-ol reacts with conc. sulfuric acid, water is eliminated. Formed are: CH2CHCH2CH3
(minor product) and CH3CHCHCH3 (major product).
(2)
(b)
(i) PCl3, PCl5, SOCl2
(ii) CH3OH/H+
(iii) CH3OH
(iv) CH3CH2CONH2
(1)
(1)
(1)
(1)
Reaction schemes shows ethene converted to ethanol using H2O / H+, ethanol to ethanoic acid
using MnO4- and
(1)
the reaction of ethanol and ethanoic acid in the presence of conc. H2SO4 to form ethyl ethanoate.(1)
(c)
10.




11.
(a)
Methanal reacts with Tollens’ reagent, forming a silver mirror on the test tube, or Fehling’s
solution to form a red-orange precipitate.
(2)
Ethanoic acid will react with sodium carbonate producing a gas (CO2).
(2)
Propan-2-ol will react with acidified potassium dichromate, changing colour from orange to green,
or acidified potassium permaganate, changing colour from purple to colourless, but will not react
with Tollen’s reagent or Fehling’s solution.
(2)
Propanone will not react with any of the reagents mentioned.
(1)
Oxidation
(1)
(b)
Warm with Tollen’s reagent (an ammoniacal solution of silver ions).
An aldehyde will produce a silver mirror inside the test tube.
(1)
(1)
or
Fehlings solution.
Mix Fehling’s A and B to form a dark blue solution of copper (II) ions in alkaline solution
(complexed with tartarate ions). Heat with the aldehyde. A yellow green ppt forms that becomes
brick red on further heating.
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