Common Organic Chemistry Reactions

1-Butene and HBr (Hydrobromic Acid)

• Reaction with hydrobromic acid: Major product
  • Alkene (nucleophile) reacts with electrophile (acid)
  • Hydrogen attaches to primary carbon; bromide ion expelled
  • Carbocation stability: Secondary carbocations > Primary carbocations
  • Bromide ion attacks carbocation, results in racemic mixture of stereoisomers
  • Products: Bromine on wedge (front) or dash (back)

Alkenes with HBr and HBr + Peroxides

• Hydrobromic acid (HBr)
  • Markovnikov addition: Bromine attaches to more substituted carbon (tertiary)
• Hydrobromic acid with Peroxides (H2O2)
  • Anti-Markovnikov addition: Bromine attaches to least substituted carbon (primary)

Cyclohexene Reactions

• Cyclohexene + Bromine (Br2) in Dichloromethane

  • Inert solvent, anti-addition reaction
  • Bromine atoms added on opposite sides resulting in mixture of enantiomers

• Cyclohexene + NBS (N-Bromosuccinimide)

  • Radical reaction, allylic bromination
  • Bromine replaces allylic hydrogen, double bond remains

Alkanes with Bromine and UV Light

• Free radical substitution reaction
  • Bromine (selective) targets most substituted hydrogen (tertiary) forming tertiary radicals
  • Chlorine (non-selective) gives mixture of products

Acid-Catalyzed Hydration of Alkenes

• Alkene + H2O + HCl
  • Protonation leads to carbocation formation
  • Hydride shift for more stable carbocation
  • Water adds to form oxonium species and eventually an alcohol
  • OH group ends up on most substituted carbon

Hydrogenation of Alkenes

• Cyclohexene + H2 and metal catalyst (Pd)
  • Addition of hydrogen across double bond, converting to alkane
• Cyclohexene + Deuterium (D2) and Palladium catalyst (Pd)
  • Cis addition of deuterium, results in meso compound

Hydroboration-Oxidation Reaction of Alkenes

• Alkene + BH3 + H2O2 + OH-
  • Anti-Markovnikov addition, OH attaches to least substituted carbon
  • Syn stereochemistry: OH and H added on same side

Oxymercuration-Demercuration

• Alkene + Hg(OAc)2 + NaBH4
  • OH group attaches to more substituted carbon

Epoxidation of Alkenes

• Alkene + mCPBA (meta-chloroperoxybenzoic acid)
  • Forms an epoxide
• Epoxide + H2O + H+
  • Epoxide opens, forming anti-diols (trans-diols)

Cis-diol Formation

• Alkene + OsO4 + NaHSO3
  • Forms cis-diols with syn addition

Hydrogenation of Alkynes

• Alkyne + H2 + Pt catalyst: Complete reduction to alkane
• Alkyne + Na/NH3: Partial reduction to trans-alkene
• Alkyne + H2 + Lindlar's Catalyst: Partial reduction to cis-alkene

Hydroboration-Oxidation of Terminal Alkynes

• Terminal Alkyne + R2BH + H2O2 + OH-
  • Produces anti-Markovnikov aldehydes after tautomerization from enol

Oxymercuration of Terminal Alkynes

• Terminal Alkyne + HgSO4 + H2SO4 + H2O
  • Produces Markovnikov ketones after tautomerization from enol

Alkylation of Acetylide Anions

• Acetylene + NaNH2 + Alkyl Halide
  • SN2 reaction forming new C-C bonds

Nucleophilic Substitution and Elimination Reactions

• 2-Bromobutane + KI + Acetone: SN2 reaction, inversion of stereochemistry
• 2-Bromobutane + H2O: SN1 and E1 reactions forming racemic alcohol and alkene products
• 2-Bromobutane + MeO- + MeOH: E2 reaction forming Zaitsev product
• Bulky Base (t-BuOK) + Bulky Alkane: Forms Hoffman product

Dehydration of Alcohols

• Secondary/Tertiary Alcohol + H2SO4 + Heat: E1 reaction forming alkene
  • Carbocation rearrangement potential

Alcohols to Halides Conversion

• Secondary alcohols + HBr, PBr3, SOCl2: Produces alkyl halides via SN1 or SN2 mechanisms

Oxidation Reactions

• Primary alcohols + PCC: Aldehyde
• Primary alcohols + Chromic acid: Carboxylic acid
• Secondary alcohols: Ketones (with both mild and strong oxidants)
• Tertiary alcohols: No reaction

Reduction Reactions

• Aldehydes/Ketones/Acid Chlorides + NaBH4: Alcohols
• Esters/Carboxylic acids + LiAlH4: Alcohols

Mechanisms

• Sodium Borohydride Reduction of Ketones: Formation of alkoxide ion then alcohol
• Grignard Reaction: Ketone to tertiary alcohol with addition of alkyl group

Grignard Reagents

• Ketone + R-MgBr + H2O: Tertiary alcohol formation