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A LevelChemistryCIEExam Questions13. An Introduction to AS Level Organic Chemistry13.2 Characteristic Organic Reactions

Characteristic Organic Reactions (CIE A Level Chemistry)

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13.2 Characteristic Organic Reactions

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13.2 Characteristic Organic Reactions

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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
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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2b2 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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2c1 mark

Fig 2.1 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 2.1
 
1-23
 

State the name of this type of bond fission.

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2d3 marks

Name three other types of reaction mechanism.

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1a6 marks

Alkenes are used as the starting point of many synthetic reaction pathways.

4-Methylpent-2-ene reacts with HBr to form 2-bromo-4-methylpentane as shown.

CH3CH(CH3)CHCHCH3 + HBr → CH3CH(CH3)CH2CHBrCH3 

Draw the mechanism of the reaction of 4-methylpent-2-ene with HBr.

  • Draw the structure of 4-methylpent-2-ene and the intermediate.
  • Include all charges, partial charges, lone pairs and curly arrows

making-2-bromo-4-methylpentane

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1b1 mark

State the role of HBr in the reaction in (a).

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1c2 marks

The halogenoalkane produced in (a) can be converted back into 4-methylpent-2-ene.

Identify the reagent(s) and conditions for this to occur.

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2a3 marks

Organic compounds can be grouped in homologous series.

i)
Describe two characteristics of a homologous series.
 
[2]
 
ii)
State the homologous series to which propene belongs.
 
[1]

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2b2 marks

Propene can be converted into a mixture of 1-chloropropane and 2-chloropropane.

i)
Identify a suitable reagent for this reaction.
 
[1]
ii)
Suggest which halogenoalkane formed in this reaction has a higher yield. Explain your answer.
 
[1]

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2c3 marks

1-chloropropane and 2-chloropropane can be converted into compounds containing the nitrile functional group.

i)
Identify a suitable reagent for the conversion of 1-chloropropane into butanenitrile, CH3CH2CH2CN.

 

[1]

 
ii)
2-chloropropane can be converted into a structural isomer of butanenitrile.
 
Name and draw the fully displayed formula of this isomer.
 
[2]

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3a3 marks

A reaction scheme involving butanone is shown in Fig. 3.1.

Butanone rightwards arrow with reaction space bold 1 on top X rightwards arrow with reaction space bold 2 on top Y rightwards arrow with reaction space bold 3 on top 2-chlorobutane

Fig. 3.1

i)
State suitable reagents for reactions 1 and 2.
 
[2]
 
ii)
Deduce the type of reaction mechanism that occurs in reaction 2.
 
[1]

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3b4 marks

Name and draw the mechanism for reaction 3 in Fig. 3.1.

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3c3 marks

Describe a chemical test and observation which would distinguish between butane and Y in Fig. 3.1.

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