Organic Chemistry Exam Review Notes

Overview

This lecture covers important topics for Organic Chemistry 1 exam number two, including:

• Stereochemistry
• SN2, SN1, E1, E2 reactions
• Alkene and alkyne reactions

Naming Compounds

Example Compound

• Compound: Cyclohexane
• Bromine Location: Carbon 1
• Methyl Location: Carbon 2
• Name: 1-bromo-2-methylcyclohexane

Chiral Centers

• Chiral Center 1 (C1):

  • Groups: Bromine (1), Tertiary Carbon (2), Secondary Carbon (3), Hydrogen (4)
  • Configuration: S --> Counterclockwise
  • Adjusted Configuration: R (due to H in front)

• Chiral Center 2 (C2):

  • Groups: Hydrogen (4), Primary Carbon (3), Secondary Carbon (2), Bromine (1)
  • Configuration: R --> Clockwise

Final Answer for Chiral Centers

• Chiral Configuration: 1R, 2R
• Complete Name: 1R, 2R-1-bromo-2-methylcyclohexane

Reaction Mechanisms

Converting 3-Methyl-1-butene to 3-Methyl-2-butanol

• Reagents:
  • A) BH3, THF, H2O
  • B) Mercury acetate and NaBH4 (Correct)
  • C) H2SO4 and H2O
  • D) MCPBA
  • E) OsO4 followed by NaHSO3

Key Reactions

• Hydroboration Oxidation (A): Poor for desired product (add to the less substituted carbon)
• Oxymercuration-Demercuration (B): Correct for desired product (add to secondary carbon)
• Acid Catalyzed Hydration (C): Rearrangement possible
• Peroxy Acids (D): Produces epoxide and diol, not desired product
• OsO4 (E): Syn-addition, not desired product

Substitution and Elimination Reactions

SN1 Reaction with Secondary Alkyl Halide

• Conditions: Polar protic solvent o Mechanism:
  1. Leaving group departs, forming a secondary carbocation.
  2. Rearrangement possible (usually to tertiary carbocation).
  3. Solvent acts as nucleophile.

Temperature Effects

• Low Temperature: Favor SN1 product
• High Temperature: Favor E1 product

Rate Laws and Statements

• SN2 Rate Law: Depends on substrate and nucleophile concentrations.
• SN1 Rate Law: Depends only on substrate concentration (nucleophile concentration has no impact).
• False Statement: Rate of an SN1 reaction does not depend on nucleophile concentration.

Reactions Involving Alkynes

Converting 1-Butyne to 2-Butanone

• Reagents: Mercury sulfate, sulfuric acid, water (Correct)
• Mechanisms:
  • Hydroboration oxidation: Converts alkyne to enol, then to aldehyde or ketone.
  • Acid-catalyzed hydration: Markovnikov addition, results in ketone.

Chirality Assessment

• Chirality Check:
  • No Plane of Symmetry: Indicates chirality.
  • Example: Molecule D is chiral (different groups on each side).

Conclusion

• Review of stereochemistry, reaction mechanisms, and product determination is crucial for preparation for the exam.
• Share with classmates for collaborative study!