haloalkanes
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mechanism for forming haloalkanes condition
free radical subsition uv light
name 3 stages of free radical subsition
initiation propagation termination
define a free radical
a species which has a single unpaired electron
why is uv light needed to start the reaction
provides the energy needed to break the Cl-Cl bond
what happens in initiation
formation of a free radical break the Cl-Cl covalent bond between 2 Cl atoms both cl atone have donated one pair of electrons into the covalent bond and when the bond breaks they take back their electron this is called homolytic fission
define propagation
uses a free radical and produces a free radical
describe propagation
chlorine radical reacts with a methane a hydrogen atom removed from alkane producing HCl and a methyl radical Cl2 reacts with the methyl radical producing another chlorine radical and haloalkane methane
define termination
to free radicals react together to form a molecule
how can the amount of further sub be reduced
an excess of alkane must be used
define nuclephile
can donate a lone pair of electrons
define nucelophilic substitution
a hydrogen atom is replaced by another atom
why is C atom attacked by a nucleophile when it’s a C-halogen bond
the C-halogen bond is polar as the halogen has greater electro negativity than the carbon atom
haloalkane to alchol reagent conditions mechanism
nucleophilic subsition aqueous NaOH, reflux
haloalkane to nitrile reagent mechanism and conditions what should you remember
nucleophilic substitution KCN aqueous and ethanol it lengths the carbon chain
haloalkane to amine reagent conditions mechanism
nuclephilic substitution excesss NH3 ethanol heat and pressure
define hydrolysis
splitting molecules using water
method for studying the speed of hydrolysis for diffrent haloalkanes
• place a measured sample of each halogenalkane into seperate test tubes and place in a water bath at 50C • into another test tube place a solution of ethanol water and aqueous silver nitrate and place in same water bath • once at equal temp add equal volumes of mixtures together • time how long it takes for a precipitate to form
formula for rate of reaction
1/time taken
why is there difference in hydrolysis between haloakanes
as bond enthalpy decreases it is easier to break the c-halogen bond the stronger the bond the harder it is to break and the slower the rate of reaction will be as more energy is required to break it
C-I is the ________ bond so ________ reaction ______ energy require to break the bond
weakest fastest less
C-CI is the ________ bond so ________ reaction ______ energy require to break the bond
strongest slowest more
haloalkane to alkene reagent conditions mechanism
elimination concentrated NaOH hot ethanol solvent
where in the ozone formed
it’s formed naturally in the upper atmosphere
how is ozone formed
stable oxygen atoms are split by UV into two oxygen radicals and one combine with an O2 molecule to form the ozone O3