Lecture 09 - Pentavalent Carbon? E2, SN1, E1. Preliminary X-ray analysis of molecules that have been designed to favor a carbon with five bonds seemed to suggest the possibility of a pentavalent intermediate in SN2 reactions,
but further analysis of these structures showed just the opposite. Boron, however, can be pentavalent in such an environment. E2, SN1 and E1 mechanisms compete with the SN2 reaction. Factors controlling E2 eliminations are illuminated by
kinetic isotope effects, stereochemistry, and regiochemistry. The competition between E2 and SN2 mechanisms influence the design of synthetic schemes, including those in which carbon nucleophiles play an important role. SN1 and E1 reactions involve
carbocation intermediates and thus the possibility that the carbon skeleton will rearrange.
(from oyc.yale.edu)
Lecture 09 - Pentavalent Carbon? E2, SN1, E1
Time
Lecture Chapters
[00:00:00]
1. Using X-Ray to Investigate the Possibility of a Pentavalent Carbon Intermediate
[00:14:07]
2. The E2 Reaction and Kinetic Isotope Effects
[00:19:51]
3. Stereochemistry & Regiochemistry of E2 Elimination
[00:31:46]
4. Strategies for Substitution in Organic Synthesis
[00:41:05]
5. SN1 and E1 Reactions - Kinetic Evidence for SN1 Substitution
[00:45:09]
6. Carbocation Intermediates: Competition and Rearrangement
References
Lecture 9 - Pentavalent Carbon? E2, SN1, E1
Instructor: Professor J. Michael McBride. Resources: Professor McBride's website resource for CHEM 125b (Spring 2011). Transcript [html]. Audio [mp3]. Download Video [mov].