Screencast 21.1
https://www.youtube.com/watch?v=onDxg-NQKvk
In this screencast, Andrew Parsons walks you through selected mechanisms to demonstrate the reduction of alkynes to alkenes.

Screencast 21.2
https://www.youtube.com/watch?v=R0o37tD9hRQ
In this screencast, Andrew Parsons defines carbocation rearrangements and walks you through examples of hydrogen atom and alkyl group 1,2-shifts.

Screencast 21.3
https://www.youtube.com/watch?v=Z5SPPtkzjr0
In this screencast, Andrew Parsons uses example ring-opening processes to discuss the use of epoxides in synthesis.