OCR A A-Level Chemistry Module 4 - Core Organic Chemistry

Homologous Series

A series of organic molecules which contain the same functional group where each successive member differs by a -CH2 group.

Functional Group

A group of atoms responsible for the chemical reactions of a compound.

General Formula

The simplest algebraic formula of a homologous series.

Empirical Formula

The simplest whole number ratio of atoms of each element in a molecule.

Molecular Formula

The actual number of atoms of each element in a molecule.

Structural Formula

Shows how atoms are bonded together in a molecule (minimum detail).

Displayed Formula

Shows all covalent bonds and all atoms present in a molecule.

Structural Isomerism

Where molecules have the same molecular formula but a different structural formula.

Stereoisomerism

Molecules that have the same molecular and structural formula but a different arrangement of atoms in space.

E/Z isomerism

A type of stereoisomerism due to restricted rotation about a C=C double bond. Two different groups must be attached to each carbon atom in the C=C group.

Hydrocarbon

A compound of hydrogen and carbon only.

Saturated hydrocarbon

Compounds containing only single C-C bonds.

Unsaturated hydrocarbons

Compounds containing one or more double C=C bonds.

Homolytic Fission

When a covalent bond breaks, each atom retains one of the bonding pair of electrons (forming radicals).

Heterolytic Fission

When a covalent bond breaks, one atom takes both the bonding electrons in the bonding pair (to form a positive and a negative ion).

Nucleophile

A species which can donate a pair of electrons - (it is attracted to areas of relative positive charge).

Electrophile

A species which can accept a pair of electrons - (it is attracted to areas of relative negative charge).

Free Radical

An atom or group of atoms with an unpaired electrons.

Addition polymerisation

Where small unsaturated molecules (monomers) join together to form a long molecular chain.

Curly Arrow

Indicates the movement of an electron pair to show either breaking or formation of a covalent bond.

Reflux

A continuous cycle of evaporation and condensation used to prevent the escape of volatile components.

Volatility

How easily a substance evaporates - a highly volatile substance evaporates easily.

Fractional Distillation

The separation of components from a mixture using their different boiling points.