Edexcel A level Chemistry
Paper 2
Nucleophile
A species that donates a lone pair of electrons. Examples include ammonia, water and cyanide.
Electrophile
A species that accepts a pair of electrons. The most common example is H+ that accepts a lone
pair of electrons from a nitrogen atom in ammonia.
Nucleophilic substitution
A substitution reaction in which a nucleophile such as ammonia is attracted to a positive charge
centre such as the functional group carbon atom of a halogenoalkane.
Hydrolysis
Breaking up a molecule using water. There are two types of hydrolysis - acidic and alkaline
Ester
A molecule that contains the COO functional group. Many esters are volatile and are found in
fragrances such as rose oil.
Ester solubility in water
The middle of the molecule has has hydrogen bonding between the oxygen of C=O and the H of
water; and also between the -O- and the H of water. The smaller the molecule the higher the
solubility in water.
Ester solubility in hexane (non-polar solvent)
The non-polar alkyl ends of the molecule form London forces with the solvent. The larger the
molecule, the greater the solubility in the hexane solvent because there are more London forces
between the solute molecule and the solvent molecule.
Ammonia
NH3
Primary amine
, CH3NH2
Secondary amine
(CH3)2NH
Tertiary amine
(CH3)3N
Free radical substitution
When a halogen atom replaces a hydrogen atom in a reaction. UV is required. At higher levels of
the halogen, the amount of substitution increases. For example, CCL4 is formed at high CL2
levels, CH3Cl is formed at low Cl2 levels. 3 steps I,P,T.
Electrophilic addition
A type of addition reaction in which an electrophile is attracted to an electron-rich centre or
atom, where it accepts a pair of electrons to form a new covalent bond.
Example - symbol equation - free radical substitution at low UV levels
Cl2 + CH4 --> CH3Cl + HCl
Example - symbol equation - free radical substitution at high UV levels
4Cl2 + CH4 --> CCl4 + 4HCl
Example - symbol equation - electrophilic addition
C2H4 + Cl2 --> C2H4Cl2
Example - symbol equation - addition polymerisation
n C2H4 --> [C2H4]n
Structural isomerism
Atoms are joined in a different order forming different structures
Stereoisomerism
Atoms are joined in the same order but they occupy different positions in space
Optical isomerism
An example of stereoisomerism where the molecule has one or more chiral centres
E/Z isomerism
Paper 2
Nucleophile
A species that donates a lone pair of electrons. Examples include ammonia, water and cyanide.
Electrophile
A species that accepts a pair of electrons. The most common example is H+ that accepts a lone
pair of electrons from a nitrogen atom in ammonia.
Nucleophilic substitution
A substitution reaction in which a nucleophile such as ammonia is attracted to a positive charge
centre such as the functional group carbon atom of a halogenoalkane.
Hydrolysis
Breaking up a molecule using water. There are two types of hydrolysis - acidic and alkaline
Ester
A molecule that contains the COO functional group. Many esters are volatile and are found in
fragrances such as rose oil.
Ester solubility in water
The middle of the molecule has has hydrogen bonding between the oxygen of C=O and the H of
water; and also between the -O- and the H of water. The smaller the molecule the higher the
solubility in water.
Ester solubility in hexane (non-polar solvent)
The non-polar alkyl ends of the molecule form London forces with the solvent. The larger the
molecule, the greater the solubility in the hexane solvent because there are more London forces
between the solute molecule and the solvent molecule.
Ammonia
NH3
Primary amine
, CH3NH2
Secondary amine
(CH3)2NH
Tertiary amine
(CH3)3N
Free radical substitution
When a halogen atom replaces a hydrogen atom in a reaction. UV is required. At higher levels of
the halogen, the amount of substitution increases. For example, CCL4 is formed at high CL2
levels, CH3Cl is formed at low Cl2 levels. 3 steps I,P,T.
Electrophilic addition
A type of addition reaction in which an electrophile is attracted to an electron-rich centre or
atom, where it accepts a pair of electrons to form a new covalent bond.
Example - symbol equation - free radical substitution at low UV levels
Cl2 + CH4 --> CH3Cl + HCl
Example - symbol equation - free radical substitution at high UV levels
4Cl2 + CH4 --> CCl4 + 4HCl
Example - symbol equation - electrophilic addition
C2H4 + Cl2 --> C2H4Cl2
Example - symbol equation - addition polymerisation
n C2H4 --> [C2H4]n
Structural isomerism
Atoms are joined in a different order forming different structures
Stereoisomerism
Atoms are joined in the same order but they occupy different positions in space
Optical isomerism
An example of stereoisomerism where the molecule has one or more chiral centres
E/Z isomerism
