SN1!!!

Today we talked about the SN1 reaction, the second of our two substitution processes. There are significant differences between the SN1 and the SN2 reaction: in terms of stereochemistry, an SN1 gives racemization instead of inversion, for steric bulk it is better to have a highly substituted substrate for an SN1 reaction (instead of an accessible carbon like we needed for the SN2), etc. It is important to be able to recognize the difference in energy profiles for the two reactions -- an SN1 is two steps and an SN2 is one step.

There is also a major difference in solvent requirements: in an SN2 reaction, polar protic solvents surround and stabilize the negatively charged nucleophile, slowing the reaction. In an SN1 reaction, you must have a polar protic solvent to stabilize the intermediate carbocation otherwise the energy level is too high and the reaction will not take place.

The podcast for today's lecture has been posted and is available on iTunes. In iTunes, go to Advanced > Subscribe to Podcasts, then enter this URL: http://itech.dickinson.edu/blog/?feed=rss2&cat=765

On Friday I hope to cover both elimination reactions, allowing us to spend next Monday and Wednesday working problems in preparation for Friday's exam.