type of reactant
| saturated | unsaturated |
|---|---|
| - compounds which contain only single bonds | - compounds which contain double or triple bonds |
| - ie alkanes | - ie alkenes, arenes |
| electrophile (electron-seeking) | nucleophile (nucleus-seeking) |
|---|---|
| - a reactant that forms a covalent bond by accepting both bonding electrons from another reactant | - a reactant that forms a covalent bond by donating both bonding electrons to another reactant |
| - electrophiles are typically positive ions or have a partial positive charge and are therefore attracted to parts of molecules which are electron rich | - nucleophiles have a lone pair of electrons and may also have a negative charge; they are therefore electron rich and are attracted to parts of molecules which are electron defficient |
| - ie | - ie |
types of reaction
| type | |
|---|---|
| addition | - occurs when two reactants combine to form a single product - characteristic of unsaturated compounds - |
| substitution | - occurs when one atom or group of atoms in a compound is replaced by a different atom or group - characteristic of saturated compounds and aromatic compounds - |
types of bond-breaking (bond fission)
| homolytic fission | heterolytic fission |
|---|---|
| - is when a covalent bond breaks by splitting the shared pair of electrons between thet wo products | - is when a covalent bond breaks with both the shared electrons going to one of the products |
| - produces two radicals, each with an unpaired electron | - produces two oppositely charged ions |
convention for depicting organic reaction mechanisms
-
a curly arrow shows movement of movement electrons within bonds and between reactants
- drawn from site of electron availability
- drawn from site of electron availability
-
a double-barbed arrow represents the motion of an electron pair
-
a single-barbed arrow, known as a fish hook, represents the movement of a single electron
- often used in reactions involving radicals