Freshman Organic Chemistry II (CHEM 125B)
A difficult exam question shows how visible and NMR spectroscopy related to long-term misassignment of the structure for the triphenylmethyl dimer. Evidence from 1970 shows that Friedel-Crafts propylation involves an SN2 mechanism, not a protonated cyclopropane. Assigning oxidation states from -4 to +4 to the carbon atoms of proposed starting material and product allows choosing whether a reagent that is oxidizing or reducing or neither is appropriate. Beyond belonging to the appropriate redox class, the reagent must have an appropriate mechanism. Alcohol oxidations by elemental bromine and by Cr+6 reagents are shown to involve familiar substitution, elimination, and addition mechanisms. Mechanistic understanding allows adjusting conditions to make oxidation selective.
00:00 - Chapter 1. Exam Question on NMR, Color, and Triphenylmethyl Dimerization
11:15 - Chapter 2. Evidence Against Protonated Cyclopropane in Friedel-Crafts Propylation
16:30 - Chapter 3. Carbon Oxidation States from -4 to +4
32:22 - Chapter 4. Mechanism of Alcohol Oxidation by Bromine
38:30 - Chapter 5. Mechanism of Alcohol Oxidation by Cr+6
Complete course materials are available at the Open Yale Courses website: http://oyc.yale.edu
This course was recorded in Spring 2011.
Tagged under: triphenylmethyl dimer,quinoid,color,Friedel-Crafts,protonated cyclopropane,carbon oxidation state,oxidation mechanism,chromium,pyridinium chlorochromate
Clip makes it super easy to turn any public video into a formative assessment activity in your classroom.
Add multiple choice quizzes, questions and browse hundreds of approved, video lesson ideas for Clip
Make YouTube one of your teaching aids - Works perfectly with lesson micro-teaching plans
1. Students enter a simple code
2. You play the video
3. The students comment
4. You review and reflect
* Whiteboard required for teacher-paced activities
With four apps, each designed around existing classroom activities, Spiral gives you the power to do formative assessment with anything you teach.
Carry out a quickfire formative assessment to see what the whole class is thinking
Create interactive presentations to spark creativity in class
Student teams can create and share collaborative presentations from linked devices
Turn any public video into a live chat with questions and quizzes