This work presents the chemistry of functional groups with an emphasis on patterns of reactivity, the consequences of the relative electronegativity of the atoms that constitute the functional groups, the role or lone pairs and the stereochemistry of reactions at a particular group. The material is presented in four sections. The first section considers functional groups involving C-X bonds such as alkyl halides, alcohols, ethers and amines. The second section considers unsymmetrical p=bonded C=X functional groups, typically the carbonyl group and the influence of these groups on adjacent centres. The third section covers symmetrical p-bonded functional groups including alkenes, alkynes and arenes and the consequences of the factors that perturb the symmetry, such as on the orientation of aromatic substitution. The final section concentrates on interconversions like oxidation and reduction, and the protection of functional groups to achieve selectivity. The chemistry of the functional groups is considered here with mechanistic rationale. Students will be encouraged to consider reactions in terms of regions of electron deficiency and excess, and hence identify the sites at which electrophiles and nucleophiles might react.