Screencast 22.1
https://www.youtube.com/watch?v=cUMZfPHb6zw
In this screencast, Andrew Parsons walks you through selected mechanisms through which poly-substituted benzenes can be synthesized.

Screencast 22.2
https://www.youtube.com/watch?v=nE8w5tXc_XA
In this screencast, Andrew Parsons introduces you to the concepts of retrosynthetic analysis and its use in planning organic syntheses.