Electron Sharing Reactions (HL IB Chemistry)

Alkanes are generally unreactive and do not react with acids, bases, or with oxidising or reducing agents. However, they will react with halogens under suitable conditions, to form halogenoalkanes.

Methane reacts with chlorine in this way to form chloromethane.

The reaction described in part (a) consists of three steps. In the first step, the Cl-Cl bond is broken to form two chlorine free radicals.

Give the equations for each step of the reaction between methane and chlorine as described in part (a).

Label each equation with the name of the correct step. You only need to provide one equation for the final step.

Chlorofluorocarbons (CFCs) are organic compounds consisting of carbon, chlorine, and fluorine atoms. They are believed to destroy the ozone layer in a similar reaction to the one described in part (a).

Ozone can be broken down by radicals formed in the atmosphere. The ozone layer is important to protecting the Earth from harmful exposure to ultraviolet light.
Without this ozone layer, life on Earth would be very different.

An example of a CFC which can damage the ozone layer is CCl₃F.

Trichloromethane is one of the products formed when dichloromethane reacts with excess chlorine in UV light.

[3]

Dichloromethane can also be formed in this reaction.

Suggest the structural formula of two bromine containing compounds that are formed during the reaction of bromine and dibromomethane in the presence of UV light.

Consider the following reaction

RCH₃ RCH₂Cl

The reaction in part a) involves a free-radical mechanism to form the chloroalkane.

Describe the mechanism, by giving equations to represent the initiation, propagation and termination steps.

Draw the full displayed formula of the haloalkane formed if excess chlorine is used in the reaction in part a).

Dichloromethyl benzene reacts with chlorine to produce trichloromethyl benzene. State the name of this type of mechanism and the required condition. 

Outline the mechanism for the reaction occurring in part a).

A reaction pathway is shown below. Compound J reacts with bromine water to form a colourless solution.

State the IUPAC name for Compound J.

Identify the reagents and conditions for the formation of Compound Y from Compound J. 

For the reaction profile outlined in the reaction profile below, state the mechanism or type of reaction for steps 1 and 2. 

Propane  1-bromopropane  Compound X  Propanal 

Step 1 ...............................................................

Step 2 ...............................................................

Outline the mechanism for step 2.

Compound X can be oxidised by the reaction with acidified potassium dichromate to give propanal. Compound X will oxidise to propanoic acid if allowed to fully oxidise. Explain how full oxidation can be prevented. 

State the following for step 1.

Reagents and conditions ..........................................

Mechanism ..........................................

This question is about free radical substitution. 

1,2-dibromoethane reacts with bromine in UV light to produce a mixture of further substituted haloalkanes. 

Write two equations showing the propagation of this chain reaction to produce 1,1,2-tribromoethane. 

Traces of 1,2,3,4-tetrabromobutane are found in the reaction mixture.