Textbook Notes (368,192)
Canada (161,707)
Chemistry (92)
CHEM 267 (7)
Chapter 17

CHEM 267: Chapter 17 Textbook Notes

2 Pages
134 Views
Unlock Document

Department
Chemistry
Course
CHEM 267
Professor
Monica Barra
Semester
Winter

Description
Chem 267 Notes Chapter 17 Notes Winter 2012 17.6 An Introduction to Pericyclic Reactions  3 major groups of pericyclic reactions: cycloaddition, electrocyclic, and sigmatrophic  Cycloaddition: +2 σ bonds, -2 π bonds  Electrocyclic: +1 σ bonds, -1 π bond  Sigmatrophic: no change in bond number  These are all concerted reactions (1 step); therefore, there are no intermediates! 17.7 Diels-Alder Reactions  In this process, a ring is formed (therefore, it is a cycloaddition reaction)  Called a [4+2] cycloaddition (2 different π systems are involved: one with 4 atoms, one with 2)  NOTE: The product of a Diels-Alder reaction is always a substituted cyclohexane! Moderate temperatures favour the formation of products in a Diels-Alder reaction  High temperatures (>200 °C) favour the reverse Diels-Alder reaction: retro Diels-Alder reaction  NOTE: Entropy (-TΔS) will always be positive for a Diels-Alder reaction!  the starting materials for a Diels-Alder reaction are a diene and a dienophile o when dienophile has no substituents (X), the reaction has a larae E and is very slow  high temp. must be used (>200 °C) for reaction to proceed (yield will still be low) o reaction will proceed faster and have a higher yield when the dienophile has an electron-withdrawing substituent (ex. halogen, carbonyl group) o when the dienophile is disubstituted, the reaction/product has stereospecificity  RULE: cis alkene produces cis disubstituted ring; trans alkene produces trans disubstituted ring  NOTE: the Diels-Alder reaction only occurs when the diene is in an s-cis conformation! o Dienes that are in an s-trans conformation will result in no reaction  when cyclopentadiene i
More Less

Related notes for CHEM 267

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit