s20 2011 week 2 day 2

s20 2011 week 2 day 2 - Chemistry S-20ab Week 2 Chemistry...

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Unformatted text preview: Chemistry S-20ab Week 2 Chemistry E-2a: Lecture 5 October 23, 2008 Introduction to Cyclic Compounds: Cyclohexanes • The most common ring in natural compounds is a 6-membered ring. Take out your model kits and make a model of cyclohexane: • How should you draw the chair conformation of cyclohexane? Reading: Section 7.2 14 93 Chemistry S-20ab Week 2 Chemistry E-2a: Lecture 5 October 23, 2008 Cyclohexanes: Interconversion of Chair Conformations • Can you accomplish this “ring flip” with your models? Reading: Section 7.2 15 94 Chemistry S-20ab Week 2 Chemistry E-2a: Lecture 5 October 23, 2008 Monosubstituted Cyclohexanes: Axial vs. Equatorial Reading: Section 7.3 16 95 Chemistry S-20ab Week 2 Chemistry E-2a: Lecture 5 October 23, 2008 Energies of Axial vs. Equatorial Substitution • The relative energy of axial vs. equatorial substitution is called the “A value” for that substituent. Generally, bulky substituents have larger A values: Reading: Section 7.3 17 96 Chemistry S-20ab Week 2 Chemistry E-2a: Lecture 5 October 23, 2008 Disubstituted Cyclohexanes Reading: Section 7.4 18 97 Chemistry S-20ab Week 2 Chemistry E-2a: Lecture 5 October 23, 2008 Stereochemistry of Alkene Addition Reactions • Predict the product(s) of each of the following reactions. Be sure to indicate stereochemistry when relevant! Br2 1. BH3 2. H2O2 , OH– 1. BH3 2. H2O2 , OH– Reading: Section 7.9 19 98 Chemistry S-20ab Week 2 Chemistry E-2a: Lecture 5 October 23, 2008 Other Cyclic and Bicyclic Compounds Reading: Sections 7.5 and 7.6 20 99 Chemistry S-20ab Week 2 Chemistry E-2a: Lecture 5 October 23, 2008 Bicyclic Compounds and Bredt!s Rule • Why is this “bridgehead alkene” so unstable? Reading: Section 7.6 21 100 Chemistry S-20ab Week 2 Chemistry E-2a: Lecture 6 October 30, 2008 Test Yourself Now! • For each of the following molecules, identify whether the molecule is chiral or achiral. For molecules that are chiral, assign R or S configurations to each stereocenter, and draw the enantiomer of the molecule. H H H CH 3 Br Br H Br Br H H 3C CH3 H 3C CH3 1 101 ...
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