Lecture 11 - Carbocations and the Mechanism of Electrophilic Addition to Alkenes and Alkynes

author: J. Michael McBride, Department of Chemistry, Yale University
recorded by: Yale University
published: Aug. 19, 2014,   recorded: February 2011,   views: 1585
released under terms of: Creative Commons Attribution No Derivatives (CC-BY-ND)
Categories

See Also:

Download Video - generic video source Download yalespan125bs2011_mcbride_lec11_01.mp4 (Video - generic video source 596.3 MB)

Download Video Download yalespan125bs2011_mcbride_lec11_01_640x360_h264.mp4 (Video 156.0 MB)

Download subtitles Download subtitles: TT/XML, RT, SRT


Help icon Streaming Video Help

Related Open Educational Resources

Related content

Report a problem or upload files

If you have found a problem with this lecture or would like to send us extra material, articles, exercises, etc., please use our ticket system to describe your request and upload the data.
Enter your e-mail into the 'Cc' field, and we will keep you updated with your request's status.
Lecture popularity: You need to login to cast your vote.
  Bibliography

Description

Substitution stabilizes alkenes, and addition of acids is thermodynamically favorable in acidic media. Addition to alkenes can involve free-radical, metal-catalyzed, and stepwise electrophilic mechanisms, the last via a cation intermediate. Electrostatics can help position an attacking electrophile like H+, but bonding en route to Markovnikov addition requires orbital mixing to form the more stable cation. Relative cation stability can be understood in terms of hyperconjugation, hybridization, and solvation or polarizability. Stabilization of a carbocation via methide shift can compete with its trapping by solvent. The curious relative rates in stepwise addition of HCl or HBr to alkynes show that halogen substituents are both electron withdrawing and electron donating.

Link this page

Would you like to put a link to this lecture on your homepage?
Go ahead! Copy the HTML snippet !

Write your own review or comment:

make sure you have javascript enabled or clear this field: