Unit 1 – Introduction – Organic Chemistry
Unit 1 - Jan 2009
Q1.
 (a)  State the general formula of the alkanes, using the letter n to denote the number of carbon atoms in each molecule.
(1)

(b)  Alkanes are used as fuels. In the petrochemical industry, useful hydrocarbons are often produced from longer chain molecules.
       Name the type of reaction shown below.
(i)   
(1)
Type of reaction ....................................

(ii)   
(1)
Type of reaction ....................................

(c)  By what type of formula are the organic molecules in (b) represented?
(1)
........................................................................................................................................................................

(d)  Another reaction carried out in industry can be represented as shown below.

(i)   Give the molecular formula of compound 2.
(1)
........................................................................................................................................................................

(ii)   Give the name of compound 2.
(1)
........................................................................................................................................................................

(e)  An equation for the reaction between methane and chlorine is:

The reaction occurs in the presence of ultraviolet (UV) light via a free-radical chain mechanism.
 The initiation step is Cl2 → 2Cl

 The next step could be

(i)   Use the following data to calculate a value for the enthalpy change for each of
       the Steps, A and B.
(3)

Answer ....................................... kJ mol−1

Answer ....................................... kJ mol−1

(ii)   Use your answer to (i) to justify which of the Steps, A or B, is the more likely.
(1)
........................................................................................................................................................................
........................................................................................................................................................................

(f)  Another halogenoalkane, bromomethane, CH3Br, is a toxic gas used to protect plants against insects.
       Health and Safety advice states that concentrations above 5 parts per million (ppm) by volume of this gas are harmful.
       A research laboratory contains 2.5 × 105 dm3 of air.  Calculate the maximum volume of bromomethane, in dm3, allowed in the laboratory to comply with the advice given.
(1)

(Total for question = 11 marks)
Unit 1 - Jun 2009
Q2.
 This question is about hydrocarbons.
(a)  Liquefied petroleum gas (LPG) is a fuel sold as an alternative to petrol.  It is a mixture of liquefied C3 and C4 alkanes.
(i)  Suggest a reason why the alkanes are liquefied.
(1)
 ............................................................................................................................................. 
 ............................................................................................................................................. 
(ii)  There are two C4 alkanes.

       Draw skeletal formulae of each of the C4 alkanes in the spaces provided.

       Name each alkane.
(4)

(iii)  Complete the following sentence.
(1)
Compounds with the same molecular formula but different structural formula

 are called .........................................

(b)  Propane, C3H8, reacts with chlorine, Cl2, in a substitution reaction.

The mechanism for this reaction is described in three stages.
(i)  Give the initiation step for this reaction and state the condition necessary for this step to occur.
(2)
Initiation step

Condition
 ............................................................................................................................................. 

(ii)  Give the TWO propagation steps for this reaction.
(2)

(iii)  Give a possible termination step for this reaction.
(1)

(c)  Myrcene, C10H16, is a naturally occurring compound which is used in perfumes.

(i)  Name the functional group in myrcene.
(1)
 ............................................................................................................................................. 
(ii)  What colour change would you observe when bromine, dissolved in an organic
        solvent, is added to myrcene?
(1)
From .............................................................................. To 

(iii)  Classify the type and mechanism of the reaction that occurs when myrcene
        reacts with bromine, Br2.
(2)
 ............................................................................................................................................. 
 ............................................................................................................................................. 

(iv)  In an experiment, 1.36 g of myrcene (molar mass: 136 g mol−1) was found to react with 0.72 dm3 of hydrogen, H2, in the presence of a nickel catalyst.
        Use this information to draw the structural formula of the product of the reaction between myrcene and hydrogen.
        [Assume the molar volume of H2 under the conditions of the experiment is 24 dm3mol−1.]
(2)
Calculation

Hence structural formula of the product

(d)  Myrcene is one of a group of compounds related to 2-methylbut-2-ene shown below.

2-methylbut-2-ene undergoes addition polymerization in a similar way to ethene.

 Draw the structural formula of the repeat unit of the polymer formed.
(2)

(Total for question = 19 marks)

Unit 1 - Jan 2010
Q3.
 This question is about the organic compounds with skeletal formulae as shown:

(a) Which compound is 2-methylpropane?
(1)
   A      
   B      
   C      
   D      

(b) Which compound has the molecular formula C5H12?
(1)
   A      
   B      
   C      
   D      
(c) Which compounds are isomers?
(1)
   A      compound A and compound C
   B      compound B and compound C
   C      compound B and compound D
   D      compound C and compound D

(d) Which compound reacts with acidified potassium manganate(VII) to form a diol?
(1)
   A      
   B      
   C      
   D      
(Total for question = 4 marks)

Q4.
 The structural formula of 5-chloro-2,2-dimethylhexane is

(Total for question = 1 mark)

Unit 1 - Jan 2011
Q5.
 A hazard that is particularly associated with alkanes is that they are
   A     corrosive.
   B     flammable.
   C     toxic by inhalation.
   D     toxic by skin absorption.
(Total for question = 1 mark)

Q6.
 This question concerns the following compounds

Which of these compounds will show geometric (E–Z or cis/trans) isomerism?
   A
   B
   C
   D
(Total for question = 1 mark)

Q7.
 The correct name for the compound shown below is

   A     2-methylbut-3-ene
   B     3-methylbut-2-ene
   C     3-methylbut-3-ene
   D     2-methylbut-2-ene
(Total for question = 1 mark)

Unit 1 - Jun 2011
Q8.
 This question is about alkanes.
(a) The skeletal formulae of two alkanes (A and B) are shown below.

      (i)   Write the general formula of the alkanes.
(1)

      (ii)  Compounds A and B are ................................................... of each other.
(1)

      (iii)  Draw the displayed formula of compound A.
(1)

      (iv)  Give the systematic name of compound B.
(1)
 ............................................................................................................................................. 

(b) The largest use for alkanes is as fuels. However, there are problems associated with the combustion of alkanes, whether complete or incomplete.
      (i)   An incomplete combustion of methane, CH4, results in the formation of carbon monoxide and water only.
Write the equation for this reaction. State symbols are not required.
(2)

      (ii)  When does incomplete combustion occur?
(1)
 ............................................................................................................................................. 
      (iii)  State two problems that result from the incomplete combustion of alkane fuels.
(2)
1 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
2 
 ............................................................................................................................................. 
    ∗(iv)  State and explain the main environmental problem arising from the complete combustion of alkane fuels.
(3)
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 (c) The reactions of organic compounds, including alkanes, may be broken down into a series of steps; this is the mechanism for the reaction. The reaction between methane and chlorine may be represented by a mechanism involving three stages - initiation, propagation and termination.
      (i)   Reaction mechanisms often involve the use of 'curly arrows'. Explain the meaning of the curly arrows shown below.
(2)

Arrow I
 ............................................................................................................................................. 
 ............................................................................................................................................. 
Arrow II
 ............................................................................................................................................. 
 ............................................................................................................................................. 
      (ii)  Using the curly arrow notation, show the initiation step of the reaction between methane and chlorine.
(2)

      (iii)  Give the two propagation steps of the reaction between methane and chlorine.
              Curly arrows are not required.
(2)

      (iv)  Suggest why a small amount of UV light can result in the formation of a large amount of product.
(1)
 ............................................................................................................................................. 
 ............................................................................................................................................. 
      (v)   Ethane is a trace product of this reaction. By means of an equation, show how the ethane is formed.
(1)

(d) Scientists never detect molecular hydrogen, H2, amongst the products of the chlorination of methane.
Use the data below to suggest why this is so.
The frequency of UV light used corresponds to an energy of about 400 kJ mol−1.

(2)
 ............................................................................................................................................. 
 ............................................................................................................................................. 
 (Total for Question = 22 marks)
Q9.
 Many organic compounds have toxic vapours. For this reason
   A    a naked flame should never be used when carrying out experiments with organic compounds.
   B    gloves should usually be worn when carrying out experiments with organic compounds.
   C    a fume cupboard should be used wherever possible when carrying out experiments with organic compounds.
   D    most experiments with organic compounds are banned in schools and colleges.
(Total for Question = 1 mark)

Unit 1 - Jan 2012
Q10.
Chloroethane can be made from ethane and chlorine in the gas phase in the presence of
       ultraviolet light. The equation for the reaction is
CH3CH3 + Cl2 → CH3CH2Cl + HCl
(a) Complete the mechanism for the reaction. Two of the steps have been given for you.
(4)

(b) This reaction gives a poor yield of chloroethane. Give the structural formula and  name of another organic product, not included in your mechanism for part (a), which could be produced in the reaction.
(2)
Formula
      ..............................................................................................................................................

(c) Chlorine gas is extremely toxic and is therefore a significant hazard. The preparation
             must be performed so as to minimise the risk to the experimenter.
     (ii)   Explain the difference between hazard and risk.
(2)
      ..............................................................................................................................................
      ..............................................................................................................................................
    (ii)   Give one precaution that you would use in this experiment to minimise the risk,
                  other than the use of a laboratory coat and safety goggles.
(1)
      ..............................................................................................................................................
      ..............................................................................................................................................
(Total for question = 9 marks)

Unit 1 - Jun 2012
Q11.
 How many structural isomers does the alkane C5H12 have?
   A    4
   B    3
   C    2
   D    1
(Total for question = 1 mark)
Q12.
The reaction of bromine with propene is an example of
   A    electrophilic substitution.
   B    free radical substitution.
   C    electrophilic addition.
   D    free radical addition.
(Total for question = 1 mark)

Unit 1 - Jun 2013
Q13.
Crude oil is a complex mixture of hydrocarbons. Initial separation is achieved by fractional distillation of the crude oil. The separate fractions are further refined to produce hydrocarbons such as decane, C10H22.

(a)  Give the general formula of alkanes.
(1)

(b)  Carbon monoxide, CO, is formed during the incomplete combustion of decane.
(i)  Write an equation for the incomplete combustion of decane, forming carbon monoxide and water only.
(1)

(ii)  Explain why incomplete combustion can occur.
(1)
 ............................................................................................................................................. 
 ............................................................................................................................................. 

(c)  'Low-sulfur fuel' is now supplied to petrol stations. The removal of sulfur from diesel and petrol reduces the emission of toxic oxides of sulfur from vehicle exhausts. One such oxide is sulfur dioxide, SO2.

The bonding in sulfur dioxide may be represented as shown below.

O = S → O

Complete the dot and cross diagram below for the SO2 molecule, showing only outer shell electrons. Use dots to represent the oxygen electrons and crosses to represent the sulfur electrons.

(3)

(d)  Another alkane produced from crude oil is heptane, C7H16. The reforming of heptane produces methylcyclohexane and only one other product. A methylcyclohexane molecule is made from a ring of six carbon atoms bonded to a methyl group.

(i)  Use the information given above to give the skeletal formula of methylcyclohexane.
(1)

(ii)  Write a balanced equation, using molecular formulae, for the reforming of heptane into methylcyclohexane and one other product. State symbols are not required.
(1)

(iii)  Suggest a reason why oil companies reform alkanes such as heptane.
(1)
 ............................................................................................................................................. 
 ............................................................................................................................................. 

(e)  Five branched-chain isomers of heptane are shown in the boxes below.

(i)  Give the systematic name of isomer A.
(1)
 ............................................................................................................................................. 

(ii)  In the empty boxes above, draw skeletal formulae for two other branched-chain isomers of C7H16, with no side-chain having more than one carbon atom.
(2)

(f)  Butane, C4H10, reacts with chlorine, Cl2, at room temperature and pressure.

C4H10 + Cl2 → C4H9Cl + HCl

(i)  What other condition is essential for this reaction?
(1)
 ............................................................................................................................................. 

(ii)  Write an equation for the initiation step of the mechanism for the above reaction. Curly arrows are not required.
(1)

(iii)  State the type of bond fission involved in the initiation step.
(1)
 ............................................................................................................................................. 

(iv)  Write equations for the two propagation steps of this mechanism. Curly arrows are not required.
(2)
First propagation step:

Second propagation step:

(v)  Write one equation for a reaction that would terminate this mechanism.
(1)

(Total for Question = 18 marks)

Q14.
What is the systematic name for the compound with the following formula?

   A    2-methyl-3-ethylbutane
   B    1,2,3-trimethylbutane
   C    2,3-dimethylpropane
   D    2,3-dimethylpentane
(Total for Question = 1 mark)

Unit 1 - Jun 2014
Q15.
 This question is about isomers of C4H8.
(a)  (i)  Alkenes contain a carbon-carbon double bond, which consists of a σ bond and a π bond.
Show, and clearly label, the σ and π bonds on the diagram below.
(2)

*(ii)  Explain why the σ bond is stronger than the π bond.
(2)
 ............................................................................................................................................. 
 ............................................................................................................................................. 

(b)  (i)  Draw the structural formula of E-but-2-ene.
(1)

(ii)  Explain why but-1-ene does not exhibit E-Z isomerism.
(1)
 ............................................................................................................................................. 
 ............................................................................................................................................. 

(iii)  Describe the result of the test for the presence of a CC bond in E-but-2-ene using bromine water. Give the displayed formula of the organic product.
(2)
Test result
Displayed formula of organic product:

(c)  Another test for CC bonds is the reaction with acidified potassium manganate(VII).
Describe the result of this test using but-1-ene and give the displayed formula of the organic product.
(2)
Test result
 ............................................................................................................................................. 
 ............................................................................................................................................. 

Displayed formula of organic product:

(d)  Another isomer of C4H8 has the structure shown below.

(i)  Name this isomer.
(1)
 ............................................................................................................................................. 

(ii)  This isomer forms an addition polymer. Show the structure of this polymer by drawing two repeat units.
(1)

(e)  'Polybutene' is the name used by cosmetic companies for a mixture of poly(but-1-ene) and poly(but-2-ene).
An American "eco-cosmetics" company says that though 'polybutene' is considered a safe ingredient in lip gloss, it is non-sustainable to use it.
Suggest one reason to justify this statement.
(1)
 ............................................................................................................................................. 
 ............................................................................................................................................. 
  
(Total for question = 13 marks)

Q16.
 What is the systematic name for the hydrocarbon shown below?

   A    1,4-dimethylbutane
   B    2,3-dimethylbutane
   C    2,3-dimethylhexane
   D    1,1,2,2-tetramethylethane
(Total for question = 1 mark)