Key Terms

  • 1,2-addition
  • 1,4-addition
  • acetylide anion
  • alkylation
  • alkyne
  • allyl group
  • anti stereochemistry
  • bromonium ion
  • carbene, R2C
  • chain-growth polymer
  • conjugated
  • enol
  • epoxide
  • glycol
  • hydrogenated
  • hydroxylation
  • hyperconjugation
  • Lindlar Catalyst
  • Markovnikov’s rule
  • methylene group
  • monomer
  • oxidation
  • oxirane
  • polymer
  • reduction
  • regiospecific reaction
  • syn stereochemistry
  • tautomer
  • vinyl group

Summary of Reactions Chapter 5

Alkene Reactions

No stereochemistry is implied unless specifically indicated with wedged, solid, and dashed lines.

1. Addition reactions of alkene

  • Addition of HCl, HBr, and HI (Section 5.1). Markovnikov regiochemistry occurs, with H adding to the less highly substituted alkene carbon and halogen adding to the more highly substituted carbon.

An alkene reacts with hydrogen halide in the presence of ether to form a product, in which C1 is bonded to a hydrogen to C2 and a halogen atom.

  • Addition of halogens Cl2 and Br2 (Section 5.4). Anti addition is observed through a halonium ion intermediate.

A reaction shows an alkene reacting with dihalide in dichloromethane to form a product, in which each carbon is bonded to a halogen group.

  • Catalytic hydrogenation (Section 5.5). Syn addition occurs.

Alkene reacts with hydrogen in the presence of palladium on carbon or platinum dioxide to form an alkane.

  • Epoxidation with a peroxyacid (Section 5.6) Syn addition occurs.

Alkene reacts with peroxyacid to form an epoxide.

  • Hydroxylation with OsO4 (Section 5.6) Syn addition occurs.

Alkene reacts with osmium tetroxide in the first step, sodium bisulfite water or osmium tetroxide, and N M O in the second step to form a diol.

2. Hydroxylation by acid-catalyzed epoxide hydrolysis (Section 5.6) Anti stereochemistry occurs.

A reaction shows an epoxide reacting with hydronium ion to form a trans-1,2-diol.

3. Electrophilic addition reactions to conjugated dienes. (Section 5.9)

Reaction scheme showing electrophilic addition of hydrobromic acid to 1,3-butadiene, branching into two products: 3-bromobut-1-ene via 1,2-addition at the top and 1-bromobut-2-ene via 1,4-addition at the bottom.

Alkyne Reactions

No stereochemistry is implied unless specifically indicated with wedged, solid, and dashed lines.

1. Preparation of Alkynes

  • Alkylation of acetylide anions (Section 5.14)

Acetylene reacts with sodium amide to produce sodium acetylide that further reacts with an alkyl bromide to give a terminal alkyne.

A terminal alkyne reacts with sodium amide to produce sodium acetylide that further reacts with an alkyl bromide to give an internal alkyne.

2. Reactions of alkynes

  • Addition of HCl and HBr (Section 5.3)

The figure shows an alkyne reacting with a hydrogen halide in ether to give a dihaloalkene. This further reacts with hydrogen halide in ether to form a tetrahaloalkane.

  • Addition of Cl2 and Br2 (Section 5.3)

The figure shows an alkyne reacting with a halide in dichloromethane to form an alkene. This further reacts with a halide and dichloromethane to form an alkane.

  • Mercuric sulfate catalyzed Hydration (Section 5.4)

Alkyne reacts with sulfuric acid, water and mercuric sulfate to form an enol. This further forms a methyl ketone.

  • Catalytic hydrogenation (Section 5.5)

The figure shows two catalytic hydrogenation reactions. The first reaction is an alkyne reacting to form an alkane. The second reaction is an alkyne reacting to form a cis alkene.

  • Conversion into acetylide anions (Section 5.7)

Alkyne reacts with sodium amide and ammonia to form sodium acetylide ion and ammonia.

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