Chemistry Mechanism practice

1. Types of reactions and
reaction mechanisms

2. Aliphatic/alicyclic
1. Free radical substitution (alkanes)
2. Electrophilic addition (alkenes)
3. Nucleophilic substitution (alcohols and haloalkanes)
4. Oxidation of alcohols
5. Elimination of alcohols

3. Free radical substitution
Alkane + halogen  haloalkane + hydrogen halide
CH4 + Cl2  CH3Cl + HCl
(a) Write the mechanism for the formation of chloromethane.
Reminder: there are 3 stages – initiation, propagation and termination.
(b) Give the condition required for the reaction
(c) State the type of bond fission taking place in the initiation stage.

4. (b) UV light
(c) Homolytic bond fission
Now do the mechanism for the below equation
CH3CH3 + IBr  CH3CH2Br + HI

5. Electrophilic addition of alkenes
Ethene + bromine  1,2-dibromoethane
(a) Write a symbol equation for the above reaction
(b) Draw the mechanism for the reaction (include charges, dipoles and curly
arrows).
(c) Give an observation for the reaction

6. Now do the mechanism for the reaction between propene and HBr to form the major
product.

7. Nucleophilic substitution
CH3CH2Cl + NaOH  CH3CH2OH + NaCl
(a) State the nucleophile in the above reaction.
(b) Draw the mechanism for the reaction.

8. OH- is the nucleophile (electron pair donor)
Methanol is reacted with sodium bromide and sulfuric acid. Write an equation/s for
the reactions taking place and apply yourself to draw the mechanism for the
reaction.
Na

9. Oxidation of alcohols
Butan-1-ol is oxidised using acidified potassium dichromate under
different conditions.
(a) State the role of potassium dichromate
(b) Write an equation for the oxidation of butan-1-ol under distillation conditions.
(c) Write an equation for the oxidation of butan-1-ol under reflux
(d) Give the colour change for the reaction.
(e) Draw an isomer of butan-1-ol that forms a ketone when oxidised using the same
reagents under reflux.
(f) Draw an isomer of butan-1-ol that cannot be oxidised using the above reagents.

10. (a) Oxidising agent
(b) CH3CH2CH2CH2OH + [O]  CH3CH2CH2CHO + H2O
(c) CH3CH2CH2CH2OH + 2[O]  CH3CH2CH2COOH + H2O
(d) Orange  green (Cr6+ -> Cr3+)
(e) CH3CH2CHOHCH3
(f)

11. Elimination of alcohols
Butan-1-ol  But-1-ene + water
(a) State the reagents and conditions required to carry out the above reaction.
(b) Write a symbol equation for the reaction.
(c) Butan-2-ol undergoes dehydration. Draw and name all the products that are
made.

12. (a) Heat under reflux, concentrated sulfuric acid/phosphoric acid.
(b)
(c)
+ H2O
Now draw the dehydration
products of