Reaction Mechanisms Flashcards
What reagents and conditions are required to react a halogen?
Reagent - Br2
Conditions - aqueous
What reagents and conditions are required to react hydrogen halides?
Reagent - HCl, HBr
Conditions - concentrated
What is an electrophile?
An atom/group of atoms which is attracted to an electron dense centre and accepts an electron pair forming a covalent bond. Usually a positive ion with a partial positive charge
What is a carbonation atom?
All carbocations (previously known as carbonium ions) carry a positive charge on a carbon atom
Explain the electrophilic addition of an alkene and hydrogen halide?
The HBr is polar as there are differences in electronegativities. Electron pair (pi bond) from double bond is attracted to slightly positive H. Double bond breaks, new C-H bond formed. HBr breaks with heterolytic fission, Br- ion formed, carbonation of C+ attracts Br- to create a bond between the two.
Why are curly arrows used?
To show the movement of electron pairs when bonds are broken or made.
Give the types of reactions
Substitution
Addition
Elimination
What is a substitution reaction?
An atom or group of atoms are replaced by a different atom/group of atoms
What is an addition reaction?
Two reactants are forming to make only one new product
What is an elimination reaction?
The removal of a small molecule from a larger one
What is homolytic fission?
When a covalent bond breaks by homolytic fission, each of the bonded atoms takes one of the shared pair of electrons from the bond (homo - same)
What is heterolytic fission?
One of the bonded atoms which breaks during the breaking of the covalent bond is taken to the atom, meaning both electrons are on the side, creating a negative ion and a positive ion.
(Hetero - different)
What is electrophile?
An atom/group that is attracted to an electron rich centre which will accept an electron forming a covalent bond - an electron pair acceptor
What happens in electrophilic addition?
A double bond breaks
