Introduction to Oxidation Reduction (Redox) Reactions

Hydrated copper (II) chloride is dissolved in water and concentrated hydrochloric acid is added to change the colour of the solution from blue to green-yellow. The ligand substitution is then reversed by adding an excess of deionised water. The structures of the complexes and the thermodynamic and equilibrium factors are discussed briefly.

We'll go step by step through how to balance an oxidation reduction (redox) reaction in acidic solution. Most importantly, both charges and atoms must balance. Here are the steps: first, calculate oxidations numbers for all the elements in the equation. Next, figure out what is being oxidized and what is being reduced. Then, write half reactions for the oxidation and reduction. After that, balance each half reaction: first, for the atoms other than O and H, then for O and H, and finally for charge by adding electrons. After being balanced, the oxidation and reduction half reactions are ready to be added back to together. Make sure that the number of electrons is the same in the oxidation and reduction half reactions. If they are not, multiply one or both of the half reactions to make the number of electrons the same. Then, combine the oxidation and reduction half reaction, canceling out stuff that appears on both sides of the equation. Lastly, do a final check to make sure that everything balances: both atoms and charge.

This short video looks at the alkaline catalysed hydrolysis of both simple and complex esters - the later making a soap in what is also known as a saponification reaction. The hydrolysis of ethyl ethanoate is shown first, followed by the hydrolysis (saponification) of tristearine. The next video in the series looks at how we determine the saponification value of a fat or oil.

In this video I look at the use of the two main reducing agents employed in organic chemistry. These are lithium aluminium hydride (lithal) and sodium borohydride. I outline the mechanism (nucleophilic addition) in which hydride ions react with C=O groups to form alcohols via alkoxide intermediates. I compare the reactivities of the two reducing agents and discuss the explosive risks associated with using lithium aluminium hydride with protic solvents such as water or methanol. A practical setup, that could be used to reduce aldehydes and ketone with lithal, is presented at the end. It is one in a series of short videos looking at the main organic practical techniques: heat & distill; reflux distillation; washing and drying in solvent extraction; recrystallisation and melting point determination; and others

Determing the Forward Rate from Experiment