11.1 Formulae, Functional Groups and Terminology

2026 Syllabus Objectives

Core:

1. Draw and interpret the displayed formula of a molecule to show all the atoms and all the bonds
2. Write and interpret general formulae of compounds in the same homologous series, limited to:
   • (a) alkanes, $C_nH_{2n+2}$
   • (b) alkenes, $C_nH_{2n}$
   • (c) alcohols, $C_nH_{2n+1}OH$
   • (d) carboxylic acids, $C_nH_{2n+1}COOH$
3. Identify a functional group as an atom or group of atoms that determine the chemical properties of a homologous series
4. State that a homologous series is a family of similar compounds with similar chemical properties due to the presence of the same functional group
5. State that a saturated compound has molecules in which all carbon–carbon bonds are single bonds
6. State that an unsaturated compound has molecules in which one or more carbon–carbon bonds are not single bonds

Supplement: 7. State that a structural formula is an unambiguous description of the way the atoms in a molecule are arranged, including $CH_2=CH_2$, $CH_3CH_2OH$, $CH_3COOCH_3$ 8. Define structural isomers as compounds with the same molecular formula, but different structural formulae, including $C_4H_{10}$ as $CH_3CH_2CH_2CH_3$ and $CH_3CH(CH_3)CH_3$ and $C_4H_8$ as $CH_3CH_2CH=CH_2$ and $CH_3CH=CHCH_3$ 9. Describe the general characteristics of a homologous series as:

• (a) having the same functional group
• (b) having the same general formula
• (c) differing from one member to the next by a $-CH_2-$ unit
• (d) displaying a trend in physical properties
• (e) sharing similar chemical properties

---