Organic Chemistry Exam Review Notes

Topics Covered

• Stereochemistry
• SN2, SN1, E1, E2 reactions
• Alkene reactions
• Alkyne reactions

Naming Compounds

1. Compound Naming
   • Example: 1-bromo-2-methylcyclohexane
   • Identify carbon chains and substituents:
     • Carbon 1: Bromine (highest priority)
     • Carbon 2: Methyl (next priority)
   • Focus on chiral centers to determine R/S configuration.

Chiral Centers

• Chiral Center 1 (Carbon 1):
  • Bromine > Tertiary carbon > Secondary carbon > Hydrogen
  • Configuration: S (reversed to R)
• Chiral Center 2 (Carbon 2):
  • Hydrogen > Primary carbon > Secondary carbon (with Bromine)
  • Configuration: R
  • Final answer: 1R, 2R, 1-bromo-2-methylcyclohexane.

Reactions of Alkenes and Alcohols

1. Convert 3-methyl-1-butene to 3-methyl-2-butanol:
   • Reagent Choice:
     • A) BH3-THF with H2O: Not suitable (primary carbon)
     • B) Mercury acetate with water + NaBH4: Produces the desired product (Markovnikov)
     • C) H2O + H2SO4: Produces alcohol on a tertiary carbon (not desired product)
     • D) MCPBA + H3O+: Produces a diol (not desired)
     • E) OsO4 + NaHSO3 + H2O: Syn addition, not desired
   • Correct Answer: B

Substitution and Elimination Reactions

1. SN1 Reaction of Secondary Alkyl Halide:

   • Mechanism: Solvolysis in polar solvent (methanol)
     • First step: Leaving group leaves, forming carbocation.
     • Rearrangement possible (stability of carbocation).
   • Major product: Ether formation (solvent acts as nucleophile).

2. Rate Laws:

   • SN2: Rate depends on nucleophile and substrate.
   • E1: Rate depends only on substrate.
   • False Statement: SN1 rate does not depend on nucleophile concentration.

Reactions of Alkynes

1. Convert 1-butyne to 2-butanone:
   • Reaction Options:
     • A) H2 with Pd: Reduces to alkane.
     • B) Li + methylamine: Forms trans-alkene.
     • C) Hydroboration-oxidation: Forms enol (tautomerizes to aldehyde).
     • D) Mercury sulfate with H2SO4 + H2O: Forms ketone (correct answer).
   • Correct Answer: D

Chirality in Compounds

1. Identifying Chiral Molecules:
   • A) Plane of symmetry: Not chiral.
   • B) Plane of symmetry: Not chiral.
   • C) Allenes: Chiral if sides have different groups.
   • D) No plane of symmetry: Chiral (correct answer).

Stereo-Specific Reactions

1. E2 Reaction:

   • Major product determined by elimination of H and leaving group (bromine).
   • Configuration: E or Z based on the groups left after reaction.

2. Final Major Product: Derived from stereochemistry of starting materials.

General Tips for Exam Preparation

• Understand reaction mechanisms and stereochemistry implications.
• Practice with naming compounds and identifying chiral centers.
• Familiarize with reaction types and expected products.
• Review rate laws for different reaction mechanisms.