UNDERSTANDINGS

Electron Sharing Reactions

• R3.3.1—A radical is a molecular entity that has an unpaired electron. Radicals are highly reactive.

  • Identify and represent radicals

• R3.3.2—Radicals are produced by homolytic fission, e.g. of halogens, in the presence of ultraviolet (UV) light or heat.

  • Explain, including with equations, the homolytic fission of halogens, known as the initiation step in a chain reaction.

• R3.3.3—Radicals take part in substitution reactions with alkanes, producing a mixture of products.

  • Explain, using equations, the propagation and termination steps in the reactions between alkanes and halogens.

Electron-Pair Sharing Reactions

• R3.4.1—A nucleophile is a reactant that forms a bond to its reaction partner (the

electrophile) by donating both bonding electrons.

• • Recognize nucleophiles in chemical reactions.

• R3.4.2—In a nucleophilic substitution reaction, a nucleophile donates an electron pair to form a new bond, as another bond breaks producing a leaving group.

  • Deduce equations with descriptions and explanations of the movement of electron pairs in nucleophilic substitution reactions.

• R3.4.3—Heterolytic fission is the breakage of a covalent bond when both bonding electrons remain with one of the two fragments formed.

  • Explain, with equations, the formation of ions by heterolytic fission.

• R3.4.4—An electrophile is a reactant that forms a bond to its reaction partner (the nucleophile) by accepting both bonding electrons from that reaction partner.

  • Recognize electrophiles in chemical reactions.

• R3.4.5—Alkenes are susceptible to electrophilic attack because of the high electron density of the carbon–carbon double bond. These reactions lead to electrophilic addition.

  • Deduce equations for the reactions of alkenes with water, halogens, and hydrogen halides.