haloalkanes

Question 1

what is hydrolysis

Answer 1

hydrolysis is a reaction with water or aqueous hydroxide ions that breaks a chemical compound into two compounds

Question 2

what ways can hydrolysis happen with haloalkanes

Answer 2

• heating with silver nitrate and ethanol added
• heating under reflux with an aquous alkali eg naoh

Question 3

what is the mechanism for this reaction called

Answer 3

nucleophillic substitution

Question 4

what is a nucleophile

Answer 4

an ion or molecule which is strongly attracted to a region of positive charge in something else . it is an electron pair donor

Question 5

draw the mechanism for bromoethane reacting with NaOH

Question 6

what happens when a haloalkane reacts with a nucleophile

Answer 6

the nucleophile replaces the halogen in a substitution reaction

Question 7

why does the halogen - carbon bond break and not one of the h-c bonds

Answer 7

the weakest bond breaks and because C-H bonds are very strong the halogen - carbon bond breaks

Question 8

what happens to the polarity of the haloalkanes

Answer 8

polarity decreases down the group because electronegativity increases as atomic radius increases , electron sheilding increases and ability to gain an electron decreases

Question 9

which haloalkane bond has the weakest bond enthalpy

Answer 9

C-I because the attraction is weaker

Question 10

how can you determine the rate of hydrolysis for different haloalkanes

Answer 10

• the rates can be determined by heating the haloalkane with aqueous silver nitrate with ethanol added
  water in the silver nitrate solution acts as a nucleophile .
  and the ethanol acts as a common solvent ,. ensuring the silver nitrate and haloalkane mix together and react .

Question 11

what happens as the hydrolysis reaction occurs

Answer 11

halide ions form . the silver nitrate reacts with it forming a precipitate of the silver halide

Question 12

what is the equation for 1-chlorobutane and silver nitrate

Answer 12

C4H9Cl(Aq) + H20(l)–>C4H9OH + AgCl~(s)+HNO39aq)

Question 13

what are organohalogen compounds

Answer 13

molecules that contain atleast one halogen atom joined to a carbon chain

Question 14

why are organohalogen compounds of slight concern

Answer 14

because they are not broken down naturally in the enviroment

Question 15

where is the ozone layer found

Answer 15

at the outer edge of the stratosphere at a height that varies of 10-40km above earths surface

Question 16

what does it do which is good

Answer 16

it absorbs damaging uv rays from the sun (UV-B) stopping them reaching the earths surface

Question 17

why is depletion of the ozone layer bad

Answer 17

more uv-b will reach our planet and damage genetics and cause a greater risk of skin cancer in organisms

Question 18

how does uv break oxygen

Answer 18

O2-> 2O

Question 19

how is ozone formed

Answer 19

O2+O<—–> O3

Question 20

what are common uses of CFCs

Answer 20

coolants in fridges
propellants in aerosols
dry cleaning solvents

Question 21

why are CFCs very stable

Answer 21

because of the strong C-H bonds

Question 22

what decreases their stability

Answer 22

-being in the stratosphere forming radicals which catalyse the breakdown of the ozone layer

Question 23

what are CFCs

Answer 23

chlorofluoro carbons (haloakanes) molecules with all their hydrogens replaced by chlorine and fluorine

Question 24

why is the Cl-C bond broken first in CFCs

Answer 24

it has the weakest bond enthalpy

Question 25

what is the initiation step for the breakdown of ozone

Answer 25

CCl3F(g)—> .CCl2F(g) + .Cl(g)
by uv

Question 26

what are the 2 propagation steps for the breakdown of ozone

Answer 26

1) Cl .(g) + O3(g) —> O2(g) + ClO .(g)

2)ClO . (g)+ O (g)—> O2(g) + Cl.(g)

Question 27

what is the termination step for the breakdown of ozone

Answer 27

Cl. (g) + Cl. (g) –> Cl2

Question 28

whats the overall equation for the breakdown of ozone

Answer 28

2O3 <—-> 3O2

Question 29

how is Cl. a cataylst

Answer 29

because it is reformed

Question 30

what other radials destroy ozone

Answer 30

nitrogen oxides formed from vehicle emissions and thunder storms can destroy ozone

Question 31

what is the initation equation for NO2 breakdown

Answer 31

NO2 (g) —> NO.(g) + O(g)

Question 32

what are the two propagation steps for the breakdown of NO2

Answer 32

1) NO.(g) + O3(g)—>O2 +NO2.
2) NO2.(g) + O –>O2 + NO.