2.2 synthesis - general Flashcards
explain homolytic fission
involves the bond breaking evenly, meaning that one electron from the shared pair in the bond goes to each atom
what does homolytic fission create?
free radicals
where does homolytic fission most commonly occur?
non-polar bonds
explain heterolytic fission
involves the bond breaking unevenly, with one atom in the bond receiving both electrons and the other atom receiving none
what does heterolytic fission create?
positive and negative ions
where does heterolytic fission most commonly occur?
in polar bonds
what are characteristics of electrophiles?
- deficient in electrons
- positive or partial positive charge
- able to accept electrons
- attracted to region of negative charge/groups that can donate electrons
what are characteristics of nucleophiles?
- rich in electrons
- negative or partial negative charge
- able to donate to electrons
- attracted to region of positive charge/groups that can accept electrons
what are examples of electrophiles?
Na+, Mg(2+), NH4+, NO2+, general carbocation
what are examples of nucleophiles?
Cl-, CN-, H2O, C=C, OH-, NH3
why do primary and secondary haloalkanes undergo SN2, while tertiary undergoes SN1?
steric hindrance - in primary and secondary, there is space for a nucleophile to approach the carbon. in tertiary there is not.
carbonation stability - tertiary CARBOCATIONS are more stable so can survive exist enough to under SN1
what reacts with haloalkanes to form ethers?
alkoxide
in which molecules can two alkenes form from elimination?
in larger molecules where the halogen/hydroxyl group makes it asymmetrical
state Markovnikov’s rule
when an asymmetrical molecule is attached to an asymmetrical alkene, the hydrogen atom becomes attached to the carbon with the most hydrogens already attached
why does Markovnikov’s rule occur?
the secondary carbocation intermediate is more stable than the primary carbocation
which is the preferred method of forming esters and why?
reacting alcohols with acid chlorides - no catalyst is required
what does a neutralisation reaction between an acid and a metal produce?
salt and hydrogen
what is the suffix of the O branch on an ether?
oxy (e.g. methoxy)
what is a common use of ethers and why?
solvents - they are relatively unreactive
why can ethers easily be removed from solutions using distillation?
they are small and volatile compounds
which family of compounds are ethers isomeric with?
alcohols
why does an ether have a lower boiling point than its isomeric alcohol?
the alcohol has hydrogen bonding present
which two ethers are soluble in water?
methoxymethane and methoxyethane
why are only two ethers soluble in water?
due to their larger molecule size
how does solubility in ethers work?
the slightly positive hydrogen on the water attracts the lone pairs of electrons on the oxygen of the ether
which two types of amines have hydrogen bonding?
primary and secondary
which type of amine has a lower boiling point than its isomeric amines?
tertiary amines (due to a lack of hydrogen bonding)
how does solubility work in amines?
lone pair of electrons on the nitrogen atom are able to form hydrogen bonds with the water
in amines, solubility decreases with…
increasing chain length
which type of reaction do amines usually undergo?
neutralisation with an acid
what is the name of a group attached to a benzene ring that isn’t a hydrogen?
a phenyl group
which atoms/groups can be added to benzene?
halogens (chlorine/bromine)
nitronium ion (NO2+)
sulfonic acid group (SO3H)
alkyl groups
why does benzene undergo electrophilic substitution?
it has delocalised electrons which make it susceptible to electrophilic attack
