International Baccalaureate IB Chemistry

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. 

Both neutral and negatively charged species should be included.

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. 

$$\text{SN2: } \mathrm{Nu^{-}} + \mathrm{R\!-\!X} \rightarrow \mathrm{R\!-\!Nu} + \mathrm{X^{-}} \quad \text{(backside attack; nucleophile donates a pair, C–X bond electrons go to }X^{-}\text{)}$$

$$\text{SN1 (ionization): } \mathrm{R\!-\!X} \rightarrow \mathrm{R^{+}} + \mathrm{X^{-}} \quad \text{(heterolytic cleavage forming a carbocation)}$$

$$\text{SN1 (nucleophilic attack): } \mathrm{R^{+}} + \mathrm{Nu^{-}} \rightarrow \mathrm{R\!-\!Nu} \quad \text{(nucleophile donates a pair to the planar carbocation)}$$

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.

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. 

Both neutral and positively‑charged species should be included.

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. 

$$\mathrm{R\!-\!CH=CH_2 + H_2O \xrightarrow{H^+} R\!-\!CH(OH)\!-\!CH_3}$$

$$\mathrm{R\!-\!CH=CH_2 + X_2 \rightarrow R\!-\!CHX\!-\!CHX\!-\!R'}$$

$$\mathrm{R\!-\!CH=CH_2 + HX \rightarrow R\!-\!CHX\!-\!CH_3}$$

A Lewis acid is an electron‑pair acceptor and a Lewis base is an electron‑pair donor.

Apply Lewis acid–base theory to inorganic and organic chemistry to identify the role of the reacting species.

When a Lewis base reacts with a Lewis acid, a coordination bond is formed. Nucleophiles are Lewis bases and electrophiles are Lewis acids.

Draw and interpret Lewis formulas of reactants and products to show coordination bond formation in Lewis acid–base reactions.

Coordination bonds are formed when ligands donate an electron pair to transition element cations, forming complex ions.

Deduce the charge on a complex ion, given the formula of the ion and ligands present.

Nucleophilic substitution reactions include the reactions between halogenoalkanes and nucleophiles.

Describe and explain the mechanisms of the reactions of primary and tertiary halogenoalkanes with nucleophiles.

The rate of the substitution reactions is influenced by the identity of the leaving group.

Predict and explain the relative rates of the substitution reactions for different halogenoalkanes.

Alkenes readily undergo electrophilic addition reactions.

Describe and explain the mechanisms of the reactions between symmetrical alkenes and halogens, water and hydrogen halides.

The relative stability of carbocations in the addition reactions between hydrogen halides and unsymmetrical alkenes can be used to explain the reaction mechanism.

Predict and explain the major product of a reaction between an unsymmetrical alkene and a hydrogen halide or water.

Electrophilic substitution reactions include the reactions of benzene with electrophiles.

Describe and explain the mechanism of the reaction between benzene and a charged electrophile, $E^+$.