haloalkanes

Question 1

mechanism for forming haloalkanes
condition

Answer 1

free radical subsition
uv light

Question 2

name 3 stages of free radical subsition

Answer 2

initiation
propagation
termination

Question 3

define a free radical

Answer 3

a species which has a single unpaired electron

Question 4

why is uv light needed to start the reaction

Answer 4

provides the energy needed to break the Cl-Cl bond

Question 5

what happens in initiation

Answer 5

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

Question 6

define propagation

Answer 6

uses a free radical and produces a free radical

Question 7

describe propagation

Answer 7

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

Question 8

define termination

Answer 8

to free radicals react together to form a molecule

Question 9

how can the amount of further sub be reduced

Answer 9

an excess of alkane must be used

Question 10

define nuclephile

Answer 10

can donate a lone pair of electrons

Question 11

define nucelophilic substitution

Answer 11

a hydrogen atom is replaced by another atom

Question 12

why is C atom attacked by a nucleophile when it’s a C-halogen bond

Answer 12

the C-halogen bond is polar as the halogen has greater electro negativity than the carbon atom

Question 13

haloalkane to alchol
reagent
conditions
mechanism

Answer 13

nucleophilic subsition
aqueous NaOH, reflux

Question 14

haloalkane to nitrile
reagent mechanism and conditions
what should you remember

Answer 14

nucleophilic substitution
KCN
aqueous and ethanol
it lengths the carbon chain

Question 15

haloalkane to amine
reagent conditions mechanism

Answer 15

nuclephilic substitution
excesss NH3
ethanol heat
and pressure

Question 16

define hydrolysis

Answer 16

splitting molecules using water

Question 17

method for studying the speed of hydrolysis for diffrent haloalkanes

Answer 17

1. place a measured sample of each halogenalkane into seperate test tubes and place in a water bath at 50C
2. into another test tube place a solution of ethanol water and aqueous silver nitrate and place in same water bath
3. once at equal temp add equal volumes of mixtures together
4. time how long it takes for a precipitate to form

Question 18

formula for rate of reaction

Answer 18

1/time taken

Question 19

why is there difference in hydrolysis between haloakanes

Answer 19

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

Question 20

C-I is the ________ bond so ________ reaction ______ energy require to break the bond

Answer 20

weakest
fastest
less

Question 21

C-CI is the ________ bond so ________ reaction ______ energy require to break the bond

Answer 21

strongest
slowest
more

Question 22

haloalkane to alkene
reagent
conditions
mechanism

Answer 22

elimination
concentrated NaOH
hot ethanol solvent

Question 23

where in the ozone formed

Answer 23

it’s formed naturally in the upper atmosphere

Question 24

how is ozone formed

Answer 24

stable oxygen atoms are split by UV into two oxygen radicals and one combine with an O2 molecule to form the ozone O3

Question 25

uses or chlorofluorocarbons

Answer 25

non toxic
inert gases
volatile

Question 26

uses of trichlorofluromethane

Answer 26

air conditioning
refrigerating

Question 27

uses of dichlorodifluoromethane

Answer 27

aerosol propellants

Question 28

CFC’s deystroy the ozone layer threw_____

Answer 28

free radical substitution

Question 29

which bond breaks in CFCl3 during initiation and why

Answer 29

C-Cl because it’s the weakest