Chem 164/261 - Lecture Outline & Assignment #3

Readings
Problems
Outline
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Readings:

Organic Chemistry, L Wade, UA Custom Edition, 2013, Volume 1 (Chem 164/261)

• Functional Group List - Inside Front Cover (also Handout)
• Chapter 6 – Stereochemistry
• Chapter 7 – Alkyl Halides: Nucleophilic Substitution & Elimination Reactions

Problems:

Do Not turn in, answers available in "Student Solutions Manual for Organic Chemistry" for LG Wade

(do all “solved problems” in chapters listed below)

• Chapter 6: 6.1 to 6.8; 6.12; 6.16; 6.19; 6.20; 6.25; 6.26; 6.28; 6.31

• Chapter 7: 7.2; 7.3; 7.7; 7.8a; 7.11; 7.12; 7.14; 7.17; 7.19; 7.20; 7.23; 7.30; 7.34; 7.41; 7.42; 7.43

Lecture Outline 3:
Stereochemistry, Alkyl Halide Substitution (SN1 & SN2) and Elimination (E1 & E2) Reactions

I. Comparison of 2 Structures:

1. Chirality and Stereoisomers
   
   
   1. The Concept of Chirality
      1. Identification of chiral objects and molecules – definitions
         1. achiral = not chiral
         2. planes of symmetry within a molecule
            
      2. Types of stereoisomers: enantiomers and diastereomers
   
   
   2. Location of Stereogenic (Chiral) centers – 4 different groups on tetrahedral atom
      1. Enantiomers and Diastereomers
      2. Meso compounds - chiral centers with plane of symmetry within molecule
      3. Molecules with more than one chiral center
      4. Recognition of chiral centers in complex molecules: cholesterol – 8 chiral centers
         1. drawing the enantiomer of cholesterol
         2. relationship of cholesterol and its potential 255 stereoisomers
      5. Fisher Projections
   
   
   3. R and S Nomenclature
      1. Rules for assignment of R and S configurations
      2. Treatment of multiple bonds – example: 3-bromo-1-pentene


2. Optical Rotation, Optical Purity and Resolution of Enantiomers
   
   
   1. Optical Rotation
      1. Measurement, factors, and absolute rotation
      2. Optical purity and enantiomeric excess
      3. Physical Properties of Enantiomers and Diastereomers
      4. Racemic mixtures – 50:50 mixtures of enantiomers
      5. Optical Purity = enantiomeric excess
   
   
   2. Separation (Resolution) of Enantiomers (e.g. Racemic mixtures)
      1. Creation of diastereomers
      2. Biological recognition
         
         
3. Nucleophilic Substitution Reactions (SN1 and SN2)
   
   
   1. General features of Nucleophilic Substitution vs. Elimination reactions
      1. Definitions: SN1 and SN2
      2. Mechanisms
   
   
   2. SN2 Reactions
      1. Stereochemistry – Walden Inversion (inversion of configuration)
      2. Substitution of primary and secondary alkyl halides
      3. Synthesis of alcohols, ethers, other halides, etc.
      4. Replacement of acetylenic hydrogen
         1. Acidity of alkynes
         2. Alkylation – Substitution Reactions
            
   3. SN1 Reactions
      1. Stereochemical aspects (loss of stereochemistry via carbocations)
      2. Substitution of tertiary alkyl halides and other tertiary carbons
      3. Synthesis of alcohols, ethers, halides



4. Elimination Reactions - E1 and E2 Competition with Substitution Reactions (SN1 and SN2)
   
   
   1. El Mechanism – Saytzeff (Zaitsev) Rule, Leaving Groups
   
   
   2. E2 Mechanism – Stereochemistry
   
   
   3. Competition of Elimination Reactions (E2 and E1 vs. SN1 and SN2)