Addition Reaction: Definition & Example

Addition Reaction: Definition & Example
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  • 0:00 Addition Reactions
  • 1:14 Rules for Addition Reactions
  • 2:25 Examples
  • 4:20 Lesson Summary
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Lesson Transcript
Instructor: Danielle Reid

Danielle has taught middle school science and has a doctorate degree in Environmental Health

Did you know that multiple bonds are often present during the addition reaction process? Explore this lesson to learn what an addition reaction is and why multiple bonds are present, and see examples of this reaction in action.

Addiction Reactions

Imagine that you are given two sets of wooden planks and asked to make something out of them - anything you want. You get out your glue, saw, nails, and hammer and start building. Eventually, you end with something like this:

While your final product might look unusual, the process you used to make it is similar to what happens in an addition reaction.

A addition reaction occurs when atoms are added to a compound containing a double or triple bond. Think of an addition reaction as two different reactants combined in a large single product that contains all the elements present in the individual reactants.

Let's take a look at those wooden planks again and pretend that they're molecules. In an addition reaction, molecule A combines with molecule B to make a single product, just like your odd-shaped, yet beautiful, work of art. As a single product, it contains the exact same type, color, and style of wood originally used.

This is a very important point, as the product of addition reactions contains all the atoms and elements originally present in the reactants being combined. Now, let's go over some basic rules for performing addition reactions.

Rules for Addition Reactions

The following three rules can be used when working with addition reactions.

  1. Addition reactions are associated with unsaturated compounds. An unsaturated compound is a compound that contains double or triple bonds. Always, always, remember that you will most likely encounter an addition reaction when your starting compound, or reactant, is unsaturated.
  2. When completed, addition reactions lead to a single compound, which is the final product. What you won't find are any leftovers or doggy bags. In chemistry, leftovers are called residues. Addition reactions will not have any reactant residues on the product side.
  3. Atoms can only be added to molecules when forming a product; nothing is eliminated or taken away. Remember that addition reactions involve the addition of an atom to a compound containing a single or double bond. Whatever the scenario, adding atoms or combining reactants, addition reactions will never involve the elimination or removal of atoms or molecules.

Now that we know the rules, let's look at an example of an addition reaction.


In organic chemistry, the most common use of addition reactions involves alkenes. Alkenes are molecules consisting of hydrocarbons (hydrogen + carbon) and double bonds. As alkenes have double bonds, can you guess what kind of compounds they are? If you just said, 'unsaturated compound,' you're correct!

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