Understanding the Reactions of Alkanes, Alkenes, and Alcohols

LO1 - Understanding the reactions of alkanes

LO1 – Understand the reactions of the alkanes.

AC 2.1 Write balanced equations for the complete and incomplete combustion reactions of the alkanes.

a) Explain the difference between complete and incomplete combustion of alkanes.

b) Write balanced equations for the following reactions:

The complete combustion of pentane.

The incomplete combustion of pentane

The complete combustion of heptane

The incomplete combustion of heptane

c) Explain why the incomplete combustion of alkanes is dangerous.

d) Outline the environmental impacts of burning fossil fuels such as the alkanes. Include an explanation of how these impacts can be mitigated.(max 300 words)

2. The alkanes will react with halogens in photochemical reactions to produce haloalkanes.

What is a photochemical reaction?

Use the formation of chloromethane from methane and chlorine in the presence of UV light, to explain the three stages involved in these photochemical reactions.

Give the equation for the overall reaction.

LO2– Understand the reactions of the alkenes.

AC 3.1 Draw and explain the mechanism for an electrophilic addition reaction of an alkene.

AC 3.2 Explain addition polymerisation.

1.a Explain why alkenes are described as being unsaturated hydrocarbons.

b. Use a diagram to illustrate how a carbon-carbon double bond forms.

c. Draw and explain the mechanism for the reaction between ethene and hydrogen bromide (HBr). In your explanation include and define the terms ‘electrophile’ and ‘carbocation’. Use curly arrows to show electron movements and indicate any partial charges.

2. Hydrogen bromide reacts with propene to form either 1-bromopropane or 2-bromopropane. Explain why 2-bromopropane is the major product.

3. Explain how the reaction with bromine can be used to test for an alkene. Include the mechanism for the reaction between hex-1-ene and bromine in your answer.

4. a Describe the process of addition polymerisation.

b. Show the repeating unit of the polymer that is formed from the addition polymerisation of chloroethene monomers. Name and give at least one use for this polymer.

LO3 – Understand the reactions of the alcohols.

AC 4.1 State the reaction conditions and write equations for the oxidation of alcohols.

AC 4.2 State the reaction conditions and write equations for the dehydration of alcohols.

AC 4.3 Draw and explain mechanisms for the formation of haloalkanes through the nucleophilic substitution reactions of alcohols.

1.a Draw displayed formulae and name at least one primary, secondary and tertiary alcohol.

b. Alcohols can be oxidised using acidified potassium dichromate.

Draw the displayed formula for butan-1-ol.

Describe the reagents and method that you would use to oxidise butan-1-ol to butanoic acid. State what you would observe and give the equation for the reaction (using [O] to represent the oxidising agent).

Describe how you would modify your method in i) to obtain butanal. Give the formula of butanal and state which homologous series it belongs to.

Draw and name the isomer of butanol which will not oxidise.

2. a Explain the term ‘dehydration’, describe the reaction conditions needed and the products formed from the dehydration of alcohols. Write an equation for the dehydration of propan-1-ol to form propene.

b.  What are the possible products formed when 2-methylbutan-2-ol is heated with concentrated sulphuric acid. Explain why two products are possible.

3. Explain why the dehydration of alcohols provides a way of manufacturing polymers such as polyethene without using fossil fuels.

4. Haloalkanes can be made through nucleophilic substitution reactions of alcohols.

Define the terms ‘nucleophile’ and ‘substitution reaction’

Draw the SN₂mechanism for the formation of bromoethane from ethanol.  

Write an equation for the preparation of 2-chlorobutane from an alcohol.