Module 2

Lesson 2.2  Addition Reactions



Key Concepts


An addition reaction involves an unsaturated organic compound and a small molecule reacting together to produce a new compound with an increased level of saturation. Usually, these reactions occur in the presence of a catalyst. Study the various types of addition reactions shown below.


Recall that unsaturated organic compounds are those containing a double or triple bond.

  1. An alkene/alkyne is reacted with hydrogen gas to form an alkane.






  2. An alkene/alkyne is reacted with a diatomic halogen molecules (such as Cl2, Br2, I2) to form a halogenated hydrocarbon.






  3. An unsaturated organic compound is reacted with a hydrogen halide.




  4. An alkene reacts with water to form an alcohol.




    Note that isomers are produced when the hydrocarbon reactant has more than two carbon atoms in the parent chain.



To better understand addition reactions, read pages 419 to 420 in the textbook.

Virtual Investigation

What happens when an alkene reacts with a diatomic halogen molecule? As you watch the video, carefully observe any changes that occur to the substances involved.

Learning Tip

Aqueous bromine is an orange-coloured liquid used to test compounds for their levels of saturation. If a compound is unsaturated (contains a double or triple bond), the orange colour of the bromine solution fades quickly.


Check Your Understanding


Complete Practice Questions 8b and 8d on page 423 in the textbook.

Check your work by clicking on the link below.

Page 423 Practice Question 8b and 8d



This is an addition reaction.


(d)


This is an addition reaction.