CAIE Chemistry AS Level Organic Chemistry Vocabulary

Vocabulary flashcards covering core definitions, structures, isomerism, reaction mechanisms, and polymers from the CAIE AS Level Organic Chemistry course.

Hydrocarbon

A compound made up of only carbon and hydrogen atoms.

Alkane

A family of simple hydrocarbons with no functional group.

Molecular formula

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

Structural formula

A representation showing the structure carbon by carbon with hydrogens and functional groups attached.

Skeletal formula

A representation showing only the bonds on the carbon skeleton, where carbon and hydrogen atoms are omitted but functional groups are shown.

Displayed formula

A representation showing how all the atoms are arranged and showing every bond between them.

Homologous series

A group of compounds with the same functional group, with successive members differing by $-CH_2-$.

Functional group

A group of atoms responsible for the characteristic reactions of an organic compound.

Saturated

Containing the most amount of hydrogen atoms possible without a double or triple carbon-carbon bond.

Unsaturated

Contains a carbon-carbon double or triple bond, meaning it does not contain the greatest possible amount of hydrogen atoms.

Homolytic fission

The splitting of a covalent bond where each atom retains one electron from the bonding pair.

Heterolytic fission

The splitting of a covalent bond where one atom retains both electrons from the bonding pair.

Free radical

An uncharged molecule with an unpaired electron.

Initiation

An initial chemical reaction which triggers further reactions.

Propagation

A secondary reaction where there is no net gain or loss of free radicals.

Termination

The final step in a chain reaction where a reactive intermediate is rendered inactive.

Nucleophile

A molecule or substance that donates electrons.

Electrophile

A molecule or substance that acts as an electron pair acceptor.

Addition reaction

A reaction where two or more molecules react together to form a larger molecule.

Substitution reaction

A reaction where an atom or group is replaced by another atom or group.

Elimination reaction

A reaction in which two substituents are removed from a molecule in a mechanism with one or two steps.

Hydrolysis

The splitting up of a compound or molecule using water.

Condensation reaction

The formation of a compound with the release of water.

Oxidation

The loss of electrons.

Reduction

The gain of electrons.

Hybridisation

The concept of forming new orbitals by combining pre-existing electron orbitals.

$sp$ hybridisation

The combination of one s orbital and one p orbital to form two equivalent orbitals that repel to give a linear shape with a $180^{\circ}$ bond angle.

$sp^2$ hybridisation

The combination of one s orbital and two p orbitals to form three equivalent orbitals giving a trigonal planar arrangement with a bond angle of $120^{\circ}$, leaving one unchanged 2p orbital perpendicular.

$sp^3$ hybridisation

The combination of one s orbital and three p orbitals to form four equivalent orbitals giving a tetrahedral arrangement with bond angles of $109.5^{\circ}$.

Sigma ($\sigma$) bond

A covalent bond formed when two orbitals overlap end-to-end, around which rotation can occur.

Pi ($\pi$) bond

A covalent bond formed when unhybridized 2p orbitals overlap above and below the plane of atoms, restricting rotation around the bond.

Structural isomers

Molecules with the same molecular formula but a different structural formula.

Chain isomerism

A type of structural isomerism that occurs when there is branching on the carbon chain.

Functional group isomerism

A type of structural isomerism where the functional group on the carbon chain changes.

Positional isomerism

A type of structural isomerism where the carbon chain backbone remains the same but the attached functional groups change position.

Stereoisomers

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

Geometrical (cis-trans) isomerism

A type of stereoisomerism occurring due to a pi bond restricting rotation around a $C=C$ double bond.

Chiral centre

An atom with four different groups bonded to it, creating non-superimposable mirror images.

Optical isomers

Stereoisomers that have the same molecular and structural formula but are non-superimposable mirror images of one another.

Hydrogenation

The process of adding two hydrogen atoms across a double bond in an alkene using hydrogen gas ($H_2$), heat, and a $Pt$ or $Ni$ catalyst.

Cracking

The process of breaking down longer chain alkanes into shorter chain alkanes and alkenes using heat and an $Al_2O_3$ catalyst.

Thermal cracking

A type of cracking requiring high temperatures (around $1000\,^{\circ}\text{C}$) and high pressures (around $70\,\text{atm}$) that produces lots of alkenes.

Catalytic cracking

A type of cracking using a zeolite catalyst, slight pressure, and high temperature (around $450\,^{\circ}\text{C}$) to produce mostly aromatic hydrocarbons and motor fuels.

Primary halogenoalkane

A halogenoalkane in which the halogen is attached to a carbon atom that is attached to one alkyl group.

Secondary halogenoalkane

A halogenoalkane in which the halogen is attached to a carbon atom that is attached to two alkyl groups.

Tertiary halogenoalkane

A halogenoalkane in which the halogen is attached to a carbon atom that is attached to three alkyl groups.

$S_N1$ mechanism

A two-step nucleophilic substitution mechanism involving the formation of a carbocation intermediate.

$S_N2$ mechanism

A one-step nucleophilic substitution mechanism where the nucleophile attacks the carbon atom from the backside simultaneously as the leaving group leaves.

Esterification

The process of heating an alcohol and a carboxylic acid together in the presence of an acid catalyst to form an ester.

Addition polymerisation

A reaction where many alkene monomers join together by opening their $C=C$ double bonds to form a long saturated polymer chain.

Repeat unit

The section of a polymer chain which repeats throughout the whole chain structure.