Organic Chemistry Reactions Overview

Introduction to Organic Chemistry Reactions

• Focus on common organic chemistry reactions for exam preparation.

Reactions of 1-Butene

• Reaction with Hydrobromic Acid (HBr):
  • Alkene (nucleophile) reacts with HBr (electrophile).
  • Hydrogen attaches to primary carbon, placing positive charge on secondary carbon.
  • Bromide ion attacks carbocation, creating a racemic mixture of products.

Markovnikov vs. Anti-Markovnikov Additions

• HBr without Peroxides:
  • Bromine adds to more substituted (tertiary) carbon.
• HBr with Peroxides (H2O2):
  • Bromine adds to least substituted (primary) carbon.

Cyclohexene Reactions

• With Bromine (Br2) in Dichloromethane:
  • Proceeds with anti-addition.
  • Produces enantiomers with one bromine on wedge, another on dash.
• With N-Bromosuccinimide (NBS):
  • Radical reaction, allylic hydrogen replaced with bromine.

Radical Reactions and Substitution

• Alkanes with Bromine in UV Light:
  • Free radical substitution, bromine replaces most substituted hydrogen.
• Bromine (Selective) vs. Chlorine (Non-selective):
  • Bromine forms tertiary radicals (more stable).
  • Chlorine gives a mixture of substitution products.

Acid-Catalyzed Hydration of Alkenes

• Reaction with Water and Hydrochloric Acid:
  • Forms hydronium ion and converts alkene to alcohol.
  • Possible carbocation rearrangement for stability.

Hydrogenation of Cyclohexene

• Using Metal Catalysts:
  • Cyclohexene reacts with hydrogen gas, turning into cycloalkane.
  • Reaction with deuterium/palladium results in cis addition.

Hydroboration-Oxidation Reactions

• Alkenes to Alcohols:
  • Anti-Markovnikov addition: OH on least substituted carbon.
  • Syn stereochemistry across the double bond (hydrogen and OH group).

Oxymercuration-Demercuration

• Converts Alkenes to Alcohols:
  • OH group adds to more substituted carbon.

Epoxidation and Diol Formation

• Using MCPBA:
  • Converts alkenes to epoxides.
  • Epoxides react with water/hydronium to form anti-diols.
• OsO4 Reaction for Cis Diols:
  • Syn addition resulting in meso compounds.

Reactions Involving Alkynes

• Reduction to Alkenes/Alkanes:
  • Hydrogen gas with platinum: full reduction to alkane.
  • Sodium/liquid ammonia: reduction to trans alkene.
  • Hydrogen/Lindlar's Catalyst: reduction to cis alkene.
• Hydroboration of Terminal Alkynes:
  • Forms aldehyde as major product.
• Mercury Sulfate Hydration of Alkynes:
  • Forms ketone from enol intermediate.

Sn1 and Sn2 Reactions

• Sn2 with Potassium Iodide/Acetone:
  • Iodide attacks, causing inversion of stereochemistry.
• Sn1 with Water:
  • Formation of racemic mixture.

E1 and E2 Reactions

• E1 with Secondary/Tertiary Alcohols:
  • Forms alkenes via carbocation rearrangement.
• E2 with Strong Bases:
  • Direct elimination leading to major alkene product.

Oxidation and Reduction Reactions

• PCC and Chromic Acid:
  • PCC oxidizes primary alcohols to aldehydes.
  • Strong oxidizers convert to carboxylic acids.
• Sodium Borohydride and Lithium Aluminum Hydride:
  • Reduces ketones and aldehydes to alcohols.
  • LAH also reduces esters and carboxylic acids.

Grignard Reagents

• React with Ketones/Aldehydes:
  • Forms alcohols by addition of carbon groups.

Conclusion

• Comprehensive overview of reactions important for organic chemistry exams.