Freshman Organic Chemistry I

Yale,, Spring 2011 , Prof. Michael McBride

Updated On 02 Feb, 19

Overview

Mechanism: How Energies and Kinetic Order Influence Reaction Rates - Peculiar Rate Laws, Bond Dissociation Energies, and Relative Reactivities - Rate and Selectivity in Radical-Chain Reactions - Electronegativity, Bond Strength, Electrostatics, and Non-Bonded Interactions - Solvation, H-Bonding, and Ionophores - Brnsted Acidity and the Generality of Nucleophilic Substitution - Nucleophilic Substitution Tools - Stereochemistry, Rate Law, Substrate, Nucleophile - Solvent, Leaving Group, Bridgehead Substitution, and Pentavalent Carbon - Pentavalent Carbon? E2, SN1, E1 - Cation Intermediates. Alkenes: Formation, Addition, and Stability - Carbocations and the Mechanism of Electrophilic Addition to Alkenes and Alkynes - Nucleophilic Participation During Electrophilic Addition to Alkenes - Addition to Form Three-Membered Rings: Carbenoids and Epoxidation.

Epoxide Opening, Dipolar Cycloaddition, and Ozonolysis - Metals and Catalysis in Alkene Oxidation, Hydrogenation, Metathesis, and Polymerization - Isoprenoids, Rubber, and Tuning Polymer Properties - Alkynes. Conjugation in Allylic Intermediates and Dienes - Linear and Cyclic Conjugation Theory. 4n+2 Aromaticity - Aromatic Transition States: Cycloaddition and Electrocyclic Reactions - Electronic and Vibrational Spectroscopy - Functional Groups and Fingerprints in IR Spectroscopy. Precession of Magnetic Nuclei - Medical MRI and Chemical NMR - Diamagnetic Anisotropy and Spin-Spin Splitting - Higher-Order Effects, Dynamics, and the NMR Time Scale.

C-13 and 2D NMR. Electrophilic Aromatic Substitution - Aromatic Substitution in Synthesis: Friedel-Crafts and Moses Gomberg - Triphenylmethyl and an Introduction to Carbonyl Chemistry - Mechanism and Equilibrium of Carbonyl Reactions - Imines and Enamines. Oxidation and Reduction - Oxidation States and Mechanisms - Periodate Cleavage, Retrosynthesis, and Green Chemistry - Measuring Bond Energies: Guest Lecture by Prof. G. Barney Ellison - Green Chemistry. Acids and Acid Derivatives - Acids and Acid Derivatives - Acyl Insertions and [gr]α-Reactivity - [gr]α-Reactivity and Condensation Reactions - Proving the Configuration of Glucose and Synthesizing Two Unnatural Products - Review: Synthesis of Cortisone.

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

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Lecture Details

Freshman Organic Chemistry II (CHEM 125B)Substition stabilizes alkenes, and addition of acids is thermodynamically favorable in acidic media. Additon 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.0000 - Chapter 1. Alkene Thermochemistry 0619 - Chapter 2. Alkene Addition Mechanisms 2241 - Chapter 3. Understanding Carbocation Stabilities3901 - Chapter 4. Skeletal Rearrangement of Carbocations 4316 - Chapter 5. Stepwise Addition to Alkynes -- Competing Influences of Halogen Complete course materials are available at the Open Yale Courses website httpoyc.yale.eduThis course was recorded in Spring 2011.