haloalkanes

Question 1

haloalkanes

Answer 1

compounds in which a halogen atom has replaced at least one of the hydrogen atoms in an alkane chain

Question 2

classification of haloalkanes

Answer 2

depends on how many alkyl groups are bonded to the carbon atom that has the halogen atom

Question 3

functional group in a haloalkane

Answer 3

is the carbon halogen bond

Question 4

why is c-halogen bond polar

Answer 4

halogen atom is more electronegative than carbon

Question 5

electrophile

Answer 5

electron pair acceptor

Question 6

nucleophile

Answer 6

electron pair donor

Question 7

examples of nucleophiles

Answer 7

OH- hydroxide ion
NH3 ammonia
H2O water
CN- cyanide ion

Question 8

nucleophile must possess…

Answer 8

a lone pair of electrons and is attracted to areas of positive charge/partial positive charge so must be negative

Question 9

nucleophilic substitution

Answer 9

an electron pair donor replaces a halogen atom

Question 10

hydrolysis

Answer 10

chemical reaction involving water or an aqueous solution of a hydroxide ion that causes the breaking of a bond in a molecule
results in the molecule being split into two products

Question 11

nucleophilic substitution reagents

Answer 11

aqueous alkali such as NaOH or KOH

Question 12

nucleophilic substitution conditions

Answer 12

heat under reflux

Question 13

heating under reflux

Answer 13

involves the continuous boiling and condensing of a liquid allowing prolonged heating of the mixture and prevents loss by evaporation preventing the liquid boiling dry

Question 14

trend in increasing reactivity of halogens

Answer 14

fluorine –> chlorine –> bromine –> iodine

Question 15

rate of hydrolysis of primary haloalkanes reagents

Answer 15

aqueous silver nitrate, AGNO3

Question 16

rate of hydrolysis of primary haloalkanes conditions

Answer 16

ethanol solvent and heat (in a water bath)

Question 17

method to measure rate of hydrolysis of primary haloalkane

Answer 17

place a set amount of haloalkane into a test tube and place in a water bath at 50 degrees
place a set amount of ethanol and aqueous silver nitrate into another test tube and place the test tube in the same water bath at 50 degrees
when the liquids in the test tubes have reached the same temperature add the contents of one test tube to the other test tube and replace in the water bath
time how long it takes for the precipitate to form in the test tube
the rate of hydrolysis =1/time

Question 18

why is the rate of hydrolysis of 1-iodobutane faster than the rate of hydrolysis of 1 chlorobutane

Answer 18

the rate of hydrolyis depends upon the strength of the carbon halogen bond
the C-I bond in 1-iodibutane is weaker than the C-Cl bond in 1-chlorobutane
less energy is needed to break the C-I bond so the rate of hydrolysis is faster

Question 19

reaction of a haloalkane and cyanide ion reagents

Answer 19

sodium cyanide (NaCN) or potassium cyanide (KCN)

Question 20

reaction of a haloalkane and cyanide ion conditions

Answer 20

dissolved in ethanol

Question 21

why can ammonia behave as a nucleophile

Answer 21

the N atom has a lone pair of electrons which can be donated

Question 22

what are CFCs

Answer 22

inert (unreactive) non toxic and non flammable

Question 23

why are CFCs no longer used

Answer 23

their use results in the depletion of the ozone layer

Question 24

alternative to CFCs

Answer 24

HFCs

Question 25

what is the ozone layer

Answer 25

region of earth's stratosphere (upper atmoshphere) that absorbs most of the sun's harmful UV radiation it contains a high concentration of ozone O3 relative to other parts of the atmosphere

Question 26

what has happened to the ozone layer

Answer 26

use of CFCs has increased the rate of ozone depletion

Question 27

how have CFCs caused the breakdown of the ozone

Answer 27

CFC molecules produce Cl radicals in the atmosphere by homolytic fission of a C-Cl bond

Question 28

initiation step using CFCl3

Answer 28

CFCl3 --> Cl radicals + CFCl2 radicals

Question 29

propagation 1 step using CFCl3

Answer 29

Cl radicals + O3 --> ClO radicals + O2

Question 30

propagation 2 step using CFCl3

Answer 30

CIO radicals + O --> Cl radicals + O2

Question 31

overall equation using CFCl3

Answer 31

O3 +O --> 2O2

Question 32

name another radical that catalyzes the breakdown of the ozone

Answer 32

NOx such as NO radicals which are produced in the atmosphere during a lightning strike or inside a jet engine

Question 33

initiation step using N2

Answer 33

N2 + O2 --> 2NO radicals

Question 34

propagation 1 step using N2

Answer 34

NO radicals + O3 --> NO2 radicals + O2

Question 35

propagation 2 step using N2

Answer 35

NO2 radicals + O --> NO radicals + O2

Question 36

overall equation using N2

Answer 36

O3 + O --> 2O2