CIE AS Chemistry

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ASChemistryCIETopic Questions3. Organic Chemistry3.1 An Introduction to AS Level Organic Chemistry

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First teaching 2020

Last exams 2024

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3.1 An Introduction to AS Level Organic Chemistry

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1a3 marks

Propane and hexane are part of the alkane homologous series.

 
i)
Define the term hydrocarbon.
 
[1]
  
ii)
Give the general formula for the homologous series of alkanes.
 
[1]
 
iii)
State the formula of an alkane containing five carbon atoms. 
 
[1]

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1b3 marks

State three characteristics of a homologous series.

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1c4 marks

Give the IUPAC names for the following aliphatic molecules in Table 1.1.

Table 1.1

Molecule  Name
CH3CH(Cl)CH3  
CH3CH2CH=CH2  
CH3CH2CH2OH  
CH3CH2CH(Br)CH2OH  

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1d4 marks

The structures of four organic compounds are shown in Fig 1.1.

 
four-organic-compounds
 
Fig 1.1
 

Complete Table 1.2 by naming the organic compounds and their functional groups.

 
Table 1.2
 
Organic compound Name Functional groups
A Propanoic acid  
B   Aldehyde
C   Aldehyde
AND
Halogenoalkane
D 2-hydroxypropanenitrile  
 

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1e2 marks

The compound 2,2-dimethylpentan-3-ol can be represented using different types of formulae.

 

Its structural formula can be shown as C(CH3)3CH(OH)CH2CH3.

 
i)
Give the empirical formula of 2,2-dimethylpentan-3-ol.
 
[1]
 
ii)
Draw the skeletal formula of 2,2-dimethylpentan-3-ol.
 
[1]

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2a3 marks

State the three different types of structural isomerism.

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2b2 marks

State the type of isomerism that occurs between the following pairs of compounds.

 
i)
2-methylpentane and 2,3-dimethylbutane.
 
[1]
 
ii)
Butan-1-ol and butan-2-ol
 
[1]

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2c3 marks

Compounds A to F are shown in Fig 2.1. 

4-1_q3d-e-ocr-a-as--a-level-easy-sq 
Fig 2.1
 
i)
State the IUPAC name for compound B.
[1]
 
ii)
State the type of structural isomerism that occurs between compounds A and D.
[1]
 
iii)
State the type of structural isomerism that occurs between compounds C and E.
[1]

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3a3 marks
Free radical substitution reactions involve hydrogen atoms in alkanes being replaced by halogen atoms.

 

Name the three steps involved in a free radical substitution reaction.

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3b2 marks

When a molecule of chlorine, Cl2, is exposed to UV light two chlorine radicals are formed.

 
i)
Write an equation for this reaction.
 
[1]
 
ii)
State the type of bond fission involved.
 
[1]

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3c1 mark

Fig 1.1 shows the breaking of a covalent bond, where the more electronegative atom B has taken both electrons from the bond to form a negative ion. 

 
Fig 1.1
 
1-23
 

State the name of this type of bond fission.

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3d3 marks

Name three other types of reaction mechanism.

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4a1 mark
Aliphatic compounds can be organised into three different categories depending on their structure. 

 

One of the categories is straight-chain. Name the other two categories of aliphatic compounds. 

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4b3 marks

Complete Table 4.1 to show the type and number of bonds in hybridised bonds.

 
Table 4.1
 
Hybridisation Number of σ bonds Number of π bonds
sp3     
sp2     
sp     

 

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4c4 marks

Four compounds are shown in Fig 4.1.

 
UdwnRtn2_3-1-4c-e-four-molecules
 
Fig 4.1
 

Complete Table 4.2 to name the shapes and bond angles of the four planar molecules.

 
Table 4.2
 
Molecule Shape Bond angle / o
Carbon dioxide  Linear  
Water   104.5
Boron trifluoride   120
Cis-platin Square planar  
 

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5a1 mark
Name the two types of stereoisomers.
 

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5b1 mark

Describe what a chiral centre is.

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5c1 mark

The structure of one optical isomer of a chlorofluorocarbon is shown in Fig 5.1.

 
1-2
 
Fig 5.1
 

Draw the structure of the other enantiomer.

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5d1 mark

The skeletal structure of a halogenoalkane is shown in Fig 5.2.

 
egodLOJO_5
 
Fig 5.2 
 

Explain why the carbon labelled a cannot be a chiral centre.

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1a
Sme Calculator3 marks

This question is about organic compounds found in living organisms.

Terpenes are a class of organic compounds widely used as fragrances in products such as perfumes. For example, one of the simpler terpenes, nerol is found in many essential oils such as lemongrass and hops. The structure of nerol is shown in Fig 1.1.

 
4-1_q1a-h-ocr-a-as--a-level-hard-sq
 
Fig 1.1
 
i)
State the molecular formula of nerol and calculate the relative molecular mass of nerol. 
 
[2]
 
ii)
Draw the displayed formula of nerol.
 
[1]

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1b3 marks

Explain whether nerol shows geometrical (cis-trans) and optical isomerism. In your answer, identify any relevant points in the structure of nerol.

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1c2 marks

Two structural isomers of nerol are linalool and geraniol. They are unsaturated alcohols with similar chemical properties that are both used in perfumes. 

 

The IUPAC names for both linalool and geraniol are shown in Table 1.1.

 
Table 1.1
 

Isomer

IUPAC name

Linalool

3,7-dimethylocta-1,6-dien-3-ol

Geraniol

3,7-dimethylocta-2,6-dien-1-ol
  

Draw the skeletal formulae for these two isomeric alcohols.

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2a3 marks

The organic compounds in Fig 2.1 are all made by living organisms.

s55z~ain_10

Fig. 2.1

i)
Give the name of compound A.
 
[1]
 
ii)
Compound A has two chiral centres and forms stereoisomers.
 
Draw one pair of optical isomers of compound A using the conventional three-dimensional representation.
 
 

 

 

 

 

 
 
[2]

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2b3 marks

Compounds B, C, D and E all show the same type of isomerism.

 

Circle the functional group(s) responsible for this isomerism on the molecules in Fig 2.1.

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2c4 marks

Compound D reacts with hydrogen chloride to form two products.

 
i)
Fully name the type of mechanism for this reaction.
 
[1]
 
ii)
One of the products formed exists as a pair of stereoisomers.
 
Draw three-dimensional diagrams of the pair of stereoisomers formed during this reaction.
 
Indicate with an asterisk (*) the chiral centre on one of the structures drawn.
 
 

 

 

 

 

 
 
[3]

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2d1 mark

Name the type of reaction occurring when compound E reacts to form methanol and deca-2,4-dienoic acid.

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3a2 marks

Ibuprofen is a common non-steroidal anti-inflammatory drug (NSAID). It contains a benzene ring and a carboxylic acid at the end of one of the branches as shown in Fig 3.1.

ibuprofen-structure-ib-hl-sq-h-14-2-q1a

Fig 3.1

Deduce the number of sigma (σ) and pi (π) bonds in ibuprofen.

 
sigma ..............................
 
pi ..............................

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3b2 marks

The ibuprofen molecule contains both sp2 and sp3 hybridised carbon atoms.

 

State the number of sp2 and sp3 hybridised carbon atoms in a molecule of ibuprofen.

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3c2 marks

Explain why the benzene ring is a planar hexagon.

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1a3 marks

A chemist is analysing a collection of organic compounds.

Some of these compounds are shown in Table 1.1.

 
Compound IUPAC name Displayed formula Skeletal formula
1 Z-2-chloro-but-2-en-1-ol 2-chloro-but-2-en-1-ol-displayed 2-chloro-but-2-en-1-ol-skeletal
2 2-chloropropanal  

 

 

 
3   _z_Z1otn_3-bromo-2-methylpropan-1-ol-displayed  
4  

 

 

 

 3-methyl-but-2-enoic-acid-skeletal
  
Table 1.1 
 

Complete Table 1.1.

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1b1 mark

State the empirical formula of compound 1.

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1c4 marks

Explain why compound 1 exists as two stereoisomers, but compound 4 does not.

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1d4 marks

Compounds 2 and 3 both exhibit the same type of isomerism.

 
i)
State the type of isomerism shown by compounds 2 and 3.
 
[1]
 
ii)
Draw the two isomers of compound 2 to explain how this type of isomerism occurs.
 
[3]

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2a3 marks

Explain how the concept of hybridisation can be used to explain the triple bond present in propyne.

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2b1 mark

Consider the molecule shown in Fig. 2.1 which contains both sigma and pi bonds.

 
q4b_14-2_medium_ib_hl_sq
 
Fig. 2.1
 

State the number of carbon atoms that exhibit sp2 hybridisation in this molecule.

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2c3 marks

Complete Table 2.1 to show the hybridisation of the nitrogen atoms in NF4+, N2H2 and N2H4.

 
 
Table 2.1
  
   NF4+ N2H2 N2H4
Hybridisation      

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3a2 marks

This question is about the structure and reactions of organic compounds.

Fig. 3.1 shows the displayed formula of a type of fuel known as gasoline. 

 
gasoline
 
Fig. 3.1
  
i)
State the IUPAC name of gasoline.
 
[1]
 
ii)
Give the general formula for the homologous series to which gasoline belongs.
 
[1]

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3b6 marks

The gasoline shown in Fig. 3.1 can react with chlorine in the presence of UV light to form various chlorinated products.

 
i)
State the type of organic mechanism used in this reaction.
 
[1]
 
ii)
Draw the skeletal formula of the four monochlorinated isomers formed when the gasoline in Fig. 3.1 reacts with chlorine. 
 
[4]
 
iii)
State the type of isomerism shown by the isomers in (ii).
 
[1]

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3c4 marks

There are two possible reactions of 1-bromopropane with sodium hydroxide.

 

Fig. 3.2 shows the mechanism for the reaction of aqueous sodium hydroxide with 1-bromopropane.

 

oh--substitution-of-1-bromopropane
 
Fig. 3.2
 
i)
State the role of the aqueous hydroxide ion in this reaction.
 
[1]
 
ii)
Name compound X. 
 
[1]
 
iii)
In different reaction conditions, an alternative reaction occurs between the hydroxide ion and 1-bromompropane to form propene and a small molecule.
 
State the reaction conditions and name the type of mechanism used in this alternative reaction.
 
[2]

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3d4 marks

Pentanal reacts with hydrogen cyanide ions to form 2-hydroxyhexanenitrile as outlined in Fig. 3.3. 

 
pentanal-to-2-hydroxyhexanenitrile
 
Fig. 3.3
 
i)
In terms of orbitals and bonding, explain why the shape of the carbonyl carbon highlighted in Fig. 3.3 can be described as trigonal planar.
 
[3]
 
ii)
State the shape and bond angle adopted by the carbonyl carbon after the reaction with hydrogen cyanide.
 
[1]

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4a3 marks

There are many different chemicals with the same molecular formulae but different arrangements of atoms in three-dimensional space. 

i)
Name the shortest straight-chain alkane to have structural isomers and the isomer.
 
[2]
 
ii)
State the type of isomerism shown by the isomers in part (i).
 
[1]

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4b7 marks

C4H8 exists as several isomers.

 
i)
Name the homologous series that C4H8 belongs to.
 
 [1]
 
ii)
Draw the skeletal formulae of two cyclic C4H8 isomers and two C4H8 isomers that show cis / trans isomerism.
 
[4]
 
iii)
There are two unsaturated C4H8 isomers that do not show cis / trans isomerism. Name these isomers and explain why they do not show cis / trans isomerism.
 
[2]

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4c6 marks

Draw the displayed formulae of the following compounds and, where appropriate, identify any chiral centres. 

  • 2,4-dimethylhexan-3-ol
  • 2,4-dimethyl-3-chloropentane
  • 2-aminobutane

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4d2 marks

1-bromopropan-1-ol exhibits optical isomerism.

 

Draw 3D representations of the two enantiomers of 1-bromopropan-1-ol.

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5a2 marks

Hybridisation of the s and p orbitals can be used to explain the shapes observed in molecules.

Explain why cyclohexane C6H12 has a puckered, non-planar shape by making reference to the C–C–C bond angles and the type of hybridisation of carbon in the molecule. 

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5b4 marks

Urea, CO(NH2)2, is present in solution in animal urine. 

 

Describe the hybridisation of C and N in the molecule, giving approximate bond angles.

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5c4 marks

Describe the hybridisation of the carbon atom in methane and explain how the concept of hybridisation can be used to explain the shape of the methane molecule.

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5d1 mark

A molecule of ethanol is shown in Fig. 5.1.

 
labelled-ethanol
 
Fig. 5.1
 

Deduce the hybridisation of the carbon atom marked in the diagram below.

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