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CHEM 125B - Freshman Organic Chemistry II

Lecture 06 - Bronsted Acidity and the Generality of Nucleophilic Substitution. The coincidentally substantial extent of ionic dissociation of water provides an example of Bronsted acidity, or nucleophilic substitution at hydrogen. Relative pKa values are insensitive enough to solvent that they provide insight on the role of energy-match, overlap, and resonance in ionic dissociation. The titration of alanine in water illustrates the experimental determination of pKa values and the phenomenon of buffering. The limited pKa scale in water can be extended dramatically by titration in other solvents, providing one of the best ways to measure many "effects" in organic chemistry. A wide range of important organic reactions discovered in the 19th century and many biochemical reactions can be understood under the rubric of nucleophilic substitution. (from oyc.yale.edu)

Lecture 06 - Bronsted Acidity and the Generality of Nucleophilic Substitution

Time Lecture Chapters
[00:00:00] 1. Solvent Influence on Ionic Dissociation
[00:04:45] 2. Bronsted Acidity as Nucleophilic Substitution at Hydrogen
[00:11:09] 3. Understanding Relative pKa in Terms of Energy Match and Overlap
[00:21:18] 4. Measuring the pKa Values of Alanine
[00:29:09] 5. Factors that Influence pKa over an Expanded Range
[00:37:06] 6. The Generality of Nucleophilic Substitution

References
Lecture 6 - Bronsted Acidity and the Generality of Nucleophilic Substitution
Instructor: Professor J. Michael McBride. Resources: Professor McBride's website resource for CHEM 125b (Spring 2011). Transcript [html]. Audio [mp3]. Download Video [mov].

Go to the Course Home or watch other lectures:

Lecture 01 - Mechanism: How Energies and Kinetic Order Influence Reaction Rates
Lecture 02 - Peculiar Rate Laws, Bond Dissociation Energies, and Relative Reactivities
Lecture 03 - Rate and Selectivity in Radical-Chain Reactions
Lecture 04 - Electronegativity, Bond Strength, Electrostatics, and Non-Bonded Interactions
Lecture 05 - Solvation, H-Bonding, and Ionophores
Lecture 06 - Bronsted Acidity and the Generality of Nucleophilic Substitution
Lecture 07 - Nucleophilic Substitution Tools - Stereochemistry, Rate Law, Substrate, Nucleophile, Leaving Group
Lecture 08 - Solvent, Leaving Group, Bridgehead Substitution, and Pentavalent Carbon
Lecture 09 - Pentavalent Carbon? E2, SN1, E1
Lecture 10 - Cation Intermediates - Alkenes: Formation, Addition, and Stability
Lecture 11 - Carbocations and the Mechanism of Electrophilic Addition to Alkenes and Alkynes
Lecture 12 - Nucleophilic Participation During Electrophilic Addition to Alkenes
Lecture 13 - Addition to Form Three-Membered Rings: Carbenoids and Epoxidation
Lecture 14 - Epoxide Opening, Dipolar Cycloaddition, and Ozonolysis
Lecture 15 - Metals and Catalysis in Alkene Oxidation, Hydrogenation, Metathesis, and Polymerization
Lecture 16 - Isoprenoids, Rubber, and Tuning Polymer Properties
Lecture 17 - Alkynes; Conjugation in Allylic Intermediates and Dienes
Lecture 18 - Linear and Cyclic Conjugation Theory; 4n+2 Aromaticity
Lecture 19 - Aromatic Transition States: Cycloaddition and Electrocyclic Reactions
Lecture 20 - Electronic and Vibrational Spectroscopy
Lecture 21 - Functional Groups and Fingerprints in IR Spectroscopy; Precession of Magnetic Nuclei
Lecture 22 - Medical MRI and Chemical NMR
Lecture 23 - Diamagnetic Anisotropy and Spin-Spin Splitting
Lecture 24 - Higher-Order Effects, Dynamics, and the NMR Time Scale
Lecture 25 - C-13 and 2D NMR - Electrophilic Aromatic Substitution
Lecture 26 - Aromatic Substitution in Synthesis: Friedel-Crafts and Moses Gomberg
Lecture 27 - Triphenylmethyl and an Introduction to Carbonyl Chemistry
Lecture 28 - Mechanism and Equilibrium of Carbonyl Reactions
Lecture 29 - Imines and Enamines; Oxidation and Reduction
Lecture 30 - Oxidation States and Mechanisms
Lecture 31 - Periodate Cleavage, Retrosynthesis, and Green Chemistry
Lecture 32 - Measuring Bond Energies: Guest Lecture by Prof. G. Barney Ellison
Lecture 33 - Green Chemistry; Acids and Acid Derivatives
Lecture 34 - Acids and Acid Derivatives
Lecture 35 - Acyl Insertions and alpha-Reactivity
Lecture 36 - alpha-Reactivity and Condensation Reactions
Lecture 37 - Proving the Configuration of Glucose and Synthesizing Two Unnatural Products
Lecture 38 - Review: Synthesis of Cortisone