Loading...

CHEM104: Organic Chemistry II

Unit 3: Conjugated Dienes   Conjugated dienes are “special alkenes” in the sense that these molecules have two C=C separated by a C-C.  This structure is known as a conjugated carbon-carbon bond or an alternating double bond.  Here, you will need to apply your knowledge of resonance to understand the behavior of reactive dienes and predict the reaction product(s).  The reactivity of these molecules is substantially different from that of alkenes which have isolated C=C.  These molecules are thus considered a different class of organic molecule.  Conjugated dienes, especially butadiene, are very important materials in the production of rubber, and thus for the tires of our cars.

Unit 3 Time Advisory
This unit will take you 6.25 hours to complete.

☐    Subunit 3.1: 2 hours

☐    Subunit 3.2: 3.25 hours

☐    Subunit 3:3: 1 hour

Unit3 Learning Outcomes
Upon successful completion of this unit, the student will be able to:
- Derive the names of dienes and understand structural and physical properties.   - Describe molecular orbitals of conjugated double bonds. - Describe the differences (in properties) among isolated, conjugated, and cumulated dienes. - Predict the product(s) of electrophilic additions (1,2 versus 1,4 additions). - Predict the products of cycloaddition reactions, and describe their stereochemistry. - Describe the polymerization process by which conjugated dienes are produced.

3.1 Nomenclature, Structural, and Physical Properties   - Assessment: University of Calgary: Professor Ian Hunt’s "Basic IUPAC Organic Nomenclature: Polyenes" Link: University of Calgary: Professor Ian Hunt’s "Basic IUPAC Organic Nomenclature: Polyenes" (HTML)
 
Instructions: Please click on the link above, and study this webpage to learn about the nomenclature of dienes (polyenes).  Then, go through the practice questions at the bottom of the webpage.  Note that polyene here means a number of alkenes.  For example, a diene has two C=C, a triene has 3 C=C etc.  Dienes are named like alkenes.  Learn about how to name dienes in this reading.

 This reading and practice problems should take approximately 30
minutes to complete.  
    
 Terms of Use: Please respect the copyright and terms of use
displayed on the webpage above. 
  • Reading: Michigan State University: Professor William Reusch’s Virtual Textbook of Organic Chemistry: “Dienes: Properties of Dienes” Link: Michigan State University: Professor William Reusch’s Virtual Textbook of Organic Chemistry: "Dienes: Properties of Dienes” (HTML)
     
    Instructions: Read the section titled “Properties of Dienes.” Because dienes have two double bonds in the same molecule, it is important to consider the positioning of these bonds relative to one another to determine properties. This reading will help you learn about the different properties of dienes when the double bonds are isolated, conjugated, or cumulated. Make sure to click on any embedded links as well as the “Click Here” buttons.
     
    Reading this section and taking notes should take approximately 30 minutes to complete.
     
    Terms of Use: This resource is licensed under a Creative Commons Attribution-NonCommercial-NoDerivs 3.0 License. It is attributed to Professor WIlliam Reusch, and the original version can be found here.

  • Reading: University of California, Davis: UC Davis Chem Wiki: "Conjugated Dienes" Link: University of California, Davis: UC Davis Chem Wiki: "Conjugated Dienes” (HTML)
     
    Instructions: Read this entire webpage and work through the problems to learn about the properties of the conjugated diene system. Note that when the double bonds in a diene are conjugated, the pi system of electrons is ‘delocalized,’ resulting in special stability and reactivity.  

    Reading this section, taking notes, and completing the problems should take approximately 1 hour.

    Terms of Use: This resource is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License. It is attributed to the University of California, Davis, ChemWiki, and the original version can be found here.

3.2 Reactivity of Conjugated Dienes   - Reading: Michigan State University: Professor William Reusch’s Virtual Textbook of Organic Chemistry: “Addition Reactions of Dienes” Link: Michigan State University: Professor William Reusch’s Virtual Textbook of Organic Chemistry: “Addition Reactions of Dienes” (HTML)
 
Instructions: Read the sections titled “Addition Reactions” and “Diels-Alder Cycloaddition.” Addition reactions of dienes differ depending on whether the double bonds are isolated or conjugated. Isolate dienes react similarly to alkenes. Conjugated dienes react by two different mechanisms to produce a 1,2- and a 1,4 addition product. Read on to learn about these addition reactions of dienes, kinetic verses thermodynamic control, and the diels-alder reaction or a conjugated diene, which gives a cycle product.

 Reading these sections and taking notes should take 1 hour to
complete.  

 Terms of Use: This resource is licensed under a [Creative Commons
Attribution-NonCommercial-NoDerivs 3.0
License](http://creativecommons.org/licenses/by-nc-nd/3.0/). It is
attributed to Professor William Reusch, and the original version can
be found
[here](http://www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/addene2.htm#dien2).
  • Web Media: YouTube: YourFormulaSheet: "Organic Chemistry Diene Reaction in 1,2 Addition and 1,4, Addition" and "Organic Chemistry Diene Dienephile Reaction" Link: YouTube: YourFormulaSheet: "Organic Chemistry Diene Reaction in 1,2 Addition and 1,4, Addition" (YouTube) and "Organic Chemistry Diene Dienephile Reaction" (YouTube)

    Instructions: Please click on the links above, and watch these two videos in their entirety (about 4:40 minutes and 6:30 minutes, respectively) to learn about the electrophilic additions to conjugated dienes and the cycloaddition reactions between a diene and a dienophile (the Diels-Alder reaction). 

    Viewing these lectures and taking notes should take approximately 15 minutes to complete.

    Terms of Use: Please respect the copyright and terms of use displayed on the webpages above. 

  • Assessment: Michigan State University: Professor William Reusch’s Virtual Textbook of Organic Chemistry: “Practice Problems” Link: Michigan State University: Professor William Reusch’s Virtual Textbook of Organic Chemistry: “Practice Problems" (HTML)

    Instructions: Please click on the link above, and scroll down to the bottom of the webpage under the “Practice Problems” section.  Select each problem set from the drop down menu, and work through these sets by following the instructions on each webpage.

    This assessment should take approximately 2 hours to complete.

    Terms of Use: Please respect the copyright and terms of use displayed on the webpage above. 

3.3 Synthetic Rubber Synthesis from Diene Polymerization   - Reading: University of California, Davis: UC Davis ChemWiki’s "Polymerization of Conjugated Dienes" Link: University of California, Davis: UC Davis ChemWiki’s "Polymerization of Conjugated Dienes" (HTML)
 
Instructions: Read this webpage and do the problems at the bottom of the page. Conjugated dienes can undergo polymerization to form rubber and other important compounds both in nature and artificially. Read on to learn about the important polymerization reaction which produces neoprene, synthetic rubber. In addition, click on and read the “Outside Links.”
 
Reading this section, taking notes, and completing the problems should take approximately 1 hour.
 
Terms of Use: This resource is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License. It is attributed to the University of California, Davis, ChemWiki, and the original version can be found here.