Chem125/126
Lewis Acids and Bases: Complexation

Experiment: Lewis Acids and Bases- Complexation

Lewis Acid/Base complexation experiment will go further in depth into salts and take a different view of acids/bases from what you have already learned thus far.

The concepts for Lewis acids and bases will be the hardest to understand in the second half of the semester.

As long as you comprehend what's going on in this lecture, you should be able to perform the experiment and understand the concepts behind the experiment.

** There are helpful hints, FYIs, and important facts throughout the lecture. Place cursor over them to learn important material!!

* Also scroll over bolded words within a sentence- they also contain additional information.

Let's get started!

Acids and Bases from a Different View.

In experiment 4, you learned about Bronsted Acid and Bases (looking ONLY at oxi-acids/bases)

• Bronsted Acid: proton donor
• Bronsted Base: proton acceptor

So what happens when an acid doesn't have any hydrogens (such as metal ions (in salt form) that will be used in this experiment?

Is it still an acid?

Here is an example that demostrates whether an acid with no hydrogrens remains as an acid!

For more information:

Introduction of Lewis Acid/Base and an explanation of what is occurring in the case of AlCl₃: http://www.youtube.com/watch?v=IhbYoVFhAww&feature=related

A change in the pH is observed, what is causing the change to occur?

What would the outcome be when NaCl is substituted?

Lewis Acids and Lewis Bases

You have been introduced to an acid (AlCl₃) that does not have any protons to donate.

How are these acids and bases (without the exchange of protons) defined?

An example of Lewis acid base reaction (something as easy as dissolving a salt into water).

Here are some examples of different cations in water.

FYI

For more information:

A visualization of the bond formation: http://www.youtube.com/watch?v=TBNT7gbOpwY

An interactive site to determine different Lewis Acid Base complexations: http://www.chem.ox.ac.uk/vrchemistry/livechem/transitionmetals_content.html

Learning how to correctly write a complexation formula.

Let's look at Lewis acid-base reactions and understand how to come up wit the correct complexation fomula.

 Here's a quiz to test if you understand the concept so far!

Part 1: Cation Acidity

Let's examine if here is any relationship of cation acidity to the properties of metal ions in general.

Putting all the information together- what can this all mean in terms of cation acidity?

How is this whole thing occurring?

 Let's look at an example to cement the concept and relate it to the lab!

Part 2A: Studies of Complex Formation with Ammonia or Hydroxide

Let's look at Lewis acid/base reaction that deals with a specific metal ion (Cu²⁺) that is used during the experiment.

Lewis Base Exchange

How come there is a Lewis Base exchange?

Application of Lewis Acid Base reactions in daily life

Addition of a new Lewis Acid (H+)

Now that we learned what happens when a new Lewis Base is introduced, does anything happen when a new Lewis Acid (H+) in added to the system?

Solubility and General Lewis Base preferences

You have been exposed to complexation reactions, so let's look at solubility and general Lewis Base preference for different groups (such as transition metals).

Here is an example that incorporates solubility and Lewis Acid/Base "partner swap" to put the concepts all together.

Here are good resources to help cement the idea of Lewis Acid-Base Reactions:

http://www.chemguide.co.uk/inorganic/complexions/aquaoh.html

http://www.chem.purdue.edu/gchelp/cchem/struct2.html