Screencast 2.1
www.youtube.com/watch?v=amnwwmIPaHU
In this screencast, Andrew Parsons walks you through different ways of representing organic compounds.

Screencast 2.2
www.youtube.com/watch?v=p3AL11Ey7Qc
In this screencast, Andrew Parsons explains the importance of being able to spot the groups of atoms in molecular structures that give them their chemical properties, using examples from nature and medicine.