paper 2 missed marks Flashcards
explain why the bromination of benzene in paracetamol (phenol) occurs more readily than the bromination of benzene
lone pair from oxygen will interact with delocalised ring of electrons - increases electron density and therefore reactivity towards electrophiles
phenol does not need a halogen carrier
benzene requires heating/reflux whereas phenol needs room temperature
why is the honeycomb structure used in car exhaust systems?
large surface area
allows gases to flow through
what type of reaction occurs between Na2O and SiO2? why is the reaction necessary?
neutralisation
Na2O - corrosive
Si - inert
how do anti bumping granules prevent bumping?
distribute heat evenly
provide surface area for bubbles to form
why is distillation instead of reflux an inefficient way to produce ethanoic acid from ethanol?
ethanol would oxidise to ethanal
ethanal has a low boiling point therefore will distil before ethanoic acid is formed
devise an experiment to compare the relative rates of hydrolysis of haloalkanes
use ethanol as a solvent and silver nitrate as solution
equal amounts of each haloalkane
measure the time taken for precipitate to form
use a water bath to control temperature
trend in hydrolysis of haloalkanes
I > Br > Cl
iodoalkane is quickest
C-I bond is weakest
define chiral/explain
carbon has 4 different substituents therefore non-superimposable
difference in nucleophilic substitutions of primary haloalkane and tertiary haloalkane using OH-
primary haloalkane and OH- both in rds
primary is SN2 therefore transition states
tertiary is SN1 therefore carbocation
purpose of starch in iodine clock reaction
starch is an indicator (reacts with the iodine)
time taken for the formation of the blue-black complex can be used to calculate rate of reaction
why is … not optically active produced by … ?
racemic mixture
carbocation is trigonometry planar therefore equal probability of attack from either side
what kind of fission forms free radicals
homolytic
why might a yield of a certain organic product be low?
reaction produces a mixture of organic products
why can phosphorus form PCl5 but nitrogen can’t form NCl5
P can expand its octet to accommodate more electrons whereas N can only accommodate 8 electrons
why does NCl3 have a higher boiling point than NF3?
More electrons and greater London forces in NCl3
permanent dipole-dipole forces stronger in NF3 as F is more electronegative
London forces are more significant than permanent dipole-dipole forces therefore more energy needed to overcome in NCl3
why do different compounds have different retention times in column chromatography?
different affinity to stationary phase
retention time depends on boiling temperature of compound
how do impurities make catalysts less effective
impurities adsorb to catalyst surface
less surface area for reactants to adsorb therefore less bonds weaken
impurities form strong bonds to surface / less likely to desorb
recrystallisation
solid dissolved in minimum hot solvent
cool product in ice bath
filter product in Büchner funnel
dry between filter paper
why are amino acids solid at room temp
they’re zwitterions
ionic bonds form between zwitterions
how do you know it is zero order for conc time graph
straight line with negative gradient - rate of reaction is independent
rate is constant
what are nucleophiles
electron pair donors
compare acid and alkali hydrolysis of esters by heating under reflux
make same product
acid hydrolysis reversible, alkaline not
acid hydrolysis produces carboxylic acid, alkaline produces carboxylate ion
acid is a catalyst, alkali is a reactant
important to add when talking about optical activity
rotates plane polarised light
