OCR F322 Heineman

Empirical Formula
The simplest whole number ratio of atoms of each element present in a compound
Molecular Formula
The actual number of atoms of each element in a molecule
General Formula
The simplest algebraic formula of a member of a homologous series. For example, the general formula of the alkanes is CnH2n+2
Structural Formula
Shows the minimal detail for the arrangement of atoms in a molecule
Displayed Formula
Shows the relative positioning of all the atoms in a molecule and the bonds between them
Skeletal Formula
A simplified organic formula, with hydrogen atoms removed from alkyl chains, leaving just a carbon skeleton and associated functional groups
Homologous Series
A series of organic compounds with the same functional group but with each successive member differing by CH2
Functional Group
The part of the organic molecule responsible for its chemical reactions
Structural Isomers
Molecules with the same molecular formula but with different structural arrangements of atoms
Stereoisomers
Compounds with the same structural formula, but with a different arrangement of the atoms in space
E/Z Isomerism
An example of stereoisomerism, in terms of restricted rotation about a double bond and the requirement for two different groups to be attached to each carbon atom of the C=C group
Cis-Trans Isomerism
A special type of E/Z isomerism in which two of the substituent groups are the same
Hydrocarbons
Organic compounds that contain carbon and hydrogen only
Saturated Hydrocarbon
A hydrocarbon with single bonds only
Unsaturated Hydrocarbon
A hydrocarbon containing carbon-to-carbon multiple bonds
Aliphatic Hydrocarbon
A hydrocarbon with carbon atoms joined together in straight or branched chains
Alicyclic Hydrocarbon
A hydrocarbon with carbon atoms joined together in a ring structure
Alkanes
The homologous series with the general formula: CnH2n+2
Nomenclature
A system of naming compounds
Alkyl Group
An alkane with a hydrogen atom removed, e.g. CH3, C2H5; Aany alkyl group is often shown as R
Homolytic Fission
The breaking of a covalent bond, with each of the bonded electrons going to each atom, forming two radicals.
Radical
A species with an unpaired electron.
Heterolytic Fission
The breaking of a covalent bond with both of the bonded electrons going to one of the atoms, forming a cation (+ ion) and an anion (- ion)
Nucleophile
An atom (or group of atoms) that is attracted to an electron-deficient centre or atom, where it donates a pair of electrons to form a new covalent bond
Electrophile
An atom (or group of atoms) that is attracted to an electron rich centre or atom, where it accepts a pair of electrons to form a new covalent bond
Addition Reaction
A reaction in which a reactant is added to an unsaturated molecule to make a saturated molecule
Substitution Reaction
A reaction in which an atom or group of atoms is replaced with a different atom or group of atoms

In a substitution reaction:
2 reactants —> 2 products

Elimination Reaction
Refers to the removal of a molecule from a saturated molecule to make an unsaturated molecule

In an elimination reaction:
1 reactant —> 2 products

Fractional Distillation
The separation of the components in a liquid mixture into fractions which differ in boiling point (and hence chemical composition) by means of distillation, typically using a fractionating column
Cracking
Refers to the breaking down of long-chained saturated hydrocarbons to form a mixture of shorter-chained alkanes and alkenes
Catalyst
A substance that increases the rate of a chemical reaction without being used up in the process
Radical Substitution
A type of substitution reaction in which a radical replaces a different atom or group of atoms
Mechanism
A sequence of steps showing the path taken by electrons in a reaction
Initiation
The first step in a radical substitution in which the free radicals are generated by Ultraviolet Radiation
Propagation
The two repeated steps in radical substitution that build up the products in a chain reaction
Termination
The step at the end of a radical substitution when two radicals combine to form a molecule
Pi-bond (? bond)
The reactive part of a double bond formed above and below the plane of the bonded atoms by sideways overlap of p-orbitals
Electrophilic addition
A type of addition reaction in which an electrophile is attracted to an electron deficient centre or atom, where it accepts a pair of electrons to form a new covalent bond
Carbocation
An organic ion in which a carbon atom has a positive charge
Curly Arrow
A symbol used in reaction mechanisms to show the movement of an electron pair in the breaking or formation of a covalent bond
Polymer
A long molecular chain built up from monomer units
Monomer
A small molecule that combines with many other monomers to form a polymer
Addition polymerisation
The process in which unsaturated alkene molecules (monomers) add on to a growing polymer chain one at a time to form a very long saturated molecular chain (the addition polymer)
Atom Economy
{Molecular Mass of the desired products/ Sum of molecular masses of all products} X 100
Activation Energy
The minimum energy required to start a reaction by the breaking of bonds
Standard Conditions
A pressure of 100 kPa (1 atmosphere), a stated temperature, usually 298K (25C), and a concentration of 1 mol dm^-3 (for reactions with aqueous solutions)
Enthalpy change of reaction
The enthalpy change that accompanies a reaction in the molar quantities expressed in a chemical equation under standard conditions, all reactants and products being in their standard states
Enthalpy change of Formation
The enthalpy change that takes place when one mole of a compound in its standard state is formed from its constituent elements in their standard states under standard conditions
Enthalpy change of combustion
The enthalpy change that takes place when one mole of a substance reacts completely with oxygen under standard conditions, all reactants and products being in their standard states
Exothermic reaction
A reaction in which the enthalpy of the products is smaller than the enthalpy of the reactants, resulting in heat loss to the surroundings (?H -ve)
Endothermic reaction
A reaction in which the enthalpy of the products is greater than the enthalpy of the reactants, resulting in heat being taken in from the surroundings (?H +ve)
Average bond enthalpy
The average enthalpy change that takes place when breaking by homolytic fission 1 mol of a give type of bond in the molecules of a gaseous species
le Chatelier’s principle
When a system in dynamic equilibrium is subjected to a change, the position of equilibrium will shift to minimise the change
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