Organic Chemistry Revision Notes

Comprehensive vocabulary revision flashcards covering homologous series, petroleum fractionation, alkanes, alkenes, alcohols, carboxylic acids, esters, and addition and condensation polymers based on Cher Sara's notes.

Homologous series

A family of organic compounds with the same functional group, the same general formula, similar chemical properties, a gradual change in physical properties, and successive members differing by $\text{—CH}_2\text{—}$.

Functional group

An atom or group of atoms that gives an organic molecule its characteristic chemical properties.

Hydrocarbon

A compound containing hydrogen and carbon only.

Saturated

An organic compound containing only $\text{C—C}$ single covalent bonds.

Unsaturated

An organic compound containing at least one carbon–carbon double bond ($\text{C=C}$).

Polyunsaturated

A compound that contains more than one $\text{C=C}$ double bond.

Isomers

Compounds that have the same molecular formula but different structural formulae.

Identify this branched isomer of butane:

Methylpropane (a branched-chain alkane isomer of butane with the molecular formula $\text{C}_4\text{H}_{10}$).

Boiling point trend in a homologous series

Boiling point increases down the series because molecules become larger, causing intermolecular forces of attraction to become stronger, meaning more energy is required to overcome these forces.

Petroleum (crude oil)

A finite, non-renewable fossil fuel consisting of a complex mixture of hydrocarbons.

Fractional distillation of petroleum

The industrial process separating petroleum into fractions in a fractionating column that is hot at the bottom and cool at the top, where fractions condense at different heights according to their boiling point ranges.

Petroleum gas

The fraction containing hydrocarbons with $1-4$ carbon atoms, having a boiling point $< 40\,^\circ\text{C}$, used as fuel for cooking and heating.

Naphtha

The petroleum fraction containing $7-14$ carbon atoms, boiling in the range of $90-150\,^\circ\text{C}$, used as feedstock (raw material) for the petrochemical industry.

Kerosene (paraffin)

The petroleum fraction containing $9-16$ carbon atoms, boiling between $150-240\,^\circ\text{C}$, used as fuel for aircraft engines and for heating and cooking.

Bitumen

The heaviest petroleum fraction containing hydrocarbons with $> 70$ carbon atoms and a boiling point $> 350\,^\circ\text{C}$, used for paving road surfaces.

Complete combustion

The exothermic burning of a fuel in a sufficient supply of oxygen to form carbon dioxide ($\text{CO}_2$) and water ($\text{H}_2\text{O}$).

Incomplete combustion

The burning of a fuel in an insufficient supply of oxygen, producing toxic carbon monoxide ($\text{CO}$) and/or soot (carbon, $\text{C}$), along with water ($\text{H}_2\text{O}$).

Alkanes

A homologous series of saturated hydrocarbons having the general formula $\text{C}_n\text{H}_{2n+2}$, which undergo combustion and substitution reactions.

Substitution reaction (alkanes)

A photochemical reaction where hydrogen atoms in an alkane are replaced one by one by chlorine or bromine atoms in the presence of ultraviolet (UV) light.

Alkenes

A homologous series of unsaturated hydrocarbons containing a carbon–carbon double bond ($\text{C=C}$) with the general formula $\text{C}_n\text{H}_{2n}$.

Cracking

The thermal decomposition process of breaking large, long-chain alkane molecules into smaller, more useful alkenes and alkanes (or hydrogen) at about $600\,^\circ\text{C}$ over a silicon dioxide ($\text{SiO}_2$) or aluminium oxide ($\text{Al}_2\text{O}_3$) catalyst.

Addition reaction

A chemical reaction in which two molecules combine to yield a single product by breaking the $\text{C=C}$ double bond, turning an unsaturated reactant into a saturated product.

Hydrogenation

An addition reaction in which an alkene reacts with hydrogen ($\text{H}_2$) at $200\,^\circ\text{C}$ in the presence of a nickel catalyst to form an alkane; used industrially to convert unsaturated vegetable oils into margarine.

Bromination

An addition reaction where an alkene reacts with aqueous bromine ($\text{Br}_2\text{(aq)}$) at room temperature with no catalyst to form a dibromoalkane.

Identify this halogenated product formed from ethene:

1,2-dibromoethane ($\text{CH}_2\text{BrCH}_2\text{Br}$), formed by adding bromine across the double bond of ethene.

Bromine water test

A diagnostic chemical test where aqueous bromine is decolourised from reddish-brown to colourless by an unsaturated alkene, but stays reddish-brown in the presence of an alkane without UV light.

Hydration of ethene

The industrial manufacture of ethanol by passing ethene and steam over a phosphoric(V) acid ($\text{H}_3\text{PO}_4$) catalyst at $300\,^\circ\text{C}$ and $60\,\text{atm}$.

Fermentation

The conversion of glucose into ethanol and carbon dioxide catalysed by yeast enzymes at $37\,^\circ\text{C}$ in the absence of oxygen: $\text{C}_6\text{H}_{12}\text{O}_6\text{(aq)} \rightarrow 2\text{C}_2\text{H}_5\text{OH}\text{(aq)} + 2\text{CO}_2\text{(g)}$.

Alcohols

A homologous series of organic compounds containing the hydroxyl functional group ($\text{—OH}$) with the general formula $\text{C}_n\text{H}_{2n+1}\text{OH}$.

Carboxylic acids

A homologous series of organic weak acids containing the carboxyl functional group ($\text{—COOH}$) with the general formula $\text{C}_n\text{H}_{2n+1}\text{COOH}$ (where $n = 0, 1, 2, \dots$).

Weak acid (carboxylic acid)

An acid that only partially ionises in aqueous solution, resulting in a low concentration of hydrogen ions ($\text{H}^+$) compared to strong acids like hydrochloric acid.

Esterification

A reversible reaction between a carboxylic acid and an alcohol warmed with a few drops of concentrated sulfuric acid ($\text{conc. H}_2\text{SO}_4$) catalyst to form an ester and water.

Identify this ester from its structural formula:

Ethyl ethanoate ($\text{CH}_3\text{COOC}_2\text{H}_5$), formed from ethanoic acid and ethanol.

Ester

A sweet-smelling, colourless, water-insoluble compound containing the ester linkage ($\text{—COO—}$), commonly used in perfumes, food flavourings, and cosmetics solvents.

Macromolecule

A very large molecule built from hundreds or thousands of atoms covalently bonded together.

Addition polymerisation

A reaction in which many unsaturated monomer molecules join together by opening their $\text{C=C}$ bonds to form a single long-chain polymer without forming any secondary products.

Identify this addition polymer repeat unit:

Poly(chloroethene) or PVC, formed by addition polymerisation of chloroethene monomers.

Condensation polymerisation

The reaction where bifunctional monomers join to form a polymer chain accompanied by the elimination of small molecules such as water ($\text{H}_2\text{O}$).

Nylon

A synthetic polyamide condensation polymer formed from a dicarboxylic acid and a diamine linked by amide bonds ($\text{—CONH—}$) with the loss of water.

Terylene

A synthetic polyester condensation polymer formed from a dicarboxylic acid and a diol linked by ester linkages ($\text{—COO—}$) with the elimination of water molecules.

Amide linkage

The functional link ($\text{—CONH—}$) connecting repeat units in polyamides such as Nylon.

Acidified potassium manganate(VII)

A powerful oxidising agent used with heat to oxidise alcohols to carboxylic acids, undergoing a distinct colour change from purple to colourless.

Acidified potassium dichromate(VI)

An oxidising agent used with heat to convert alcohols into carboxylic acids, characterised by a colour shift from orange to green.