Haloalkanes

Question 1

describe the reactivity of haloalkanes?

Answer 1

polar C-Halogen bond due to halogen being more electronegative therefore positive carbon attracts nucleophiles

Question 2

what are some nucleophiles

Answer 2

OH-
H20
NH3

Question 3

what are nucleophiles?

Answer 3

species that donate a lone pair of electrons to an electron deficient carbon atom to form a covalent bond

Question 4

what happens when haloalkane reacts with nucleophile

Answer 4

nucleophile replaces halogen in a substitution reaction

Question 5

what is this reaction called?

Answer 5

nucleophilic substitution

Question 6

describe the hydrolysis of a haloalkane?

Answer 6

OH- nucleophile is attracted to a slightly carbon atom forming a new bond between the oxygen atom of the hydroxide ion and the carbon atom. Carbon-halogen bond breaks by heterolytic fission forming a halide ion.

Question 7

during the hydrolysis of a haloalkane, why does the OH- nucleophile go around the carbon atom

Answer 7

so it minimised repulsion between nucleophile and slightly negative halogen atom

Question 8

how are haloalkanes converted to alcohols?

Answer 8

mixture of haloalkane and sodium hydroxide is heated under relux to obtain a good yield

Question 9

why do iodoalkanes react faster than bromoalkanes with nucleophiles>

Answer 9

carbon-iodine bond is weaker therefore less energy is required to break bond

Question 10

how do you measure the rate of hydrolysis of primary haloalkanes?

Answer 10

carry out the hydrolysis of haloalkanes in the presence of aqueous silver nitrate which reacts with halide ions that are produced to form a precipitate of silver halide

Question 11

why does a tertiary haloalkane react faster than primary haloalkane?

Answer 11

tertiary haloalkane reacts by a two-step mechanism whereas primary haloalkane reacts by one-step mechanism

Question 12

what is the two-step mechanism for hydrolysis of tertiary haloalkane

Answer 12

1) carbon-halogen bond of tertiary haloalkane breaks by heterolytic fission
2) a OH- ion attacks the carbocation to form the organic product

Question 13

what is an organohalogen compound

Answer 13

molecule that contains at least one halogen atom joined to a carbon chain

Question 14

where are organohalogen compounds in

Answer 14

pesticides

Question 15

what does the ozone layer do

Answer 15

ozone absorbs UV-B rays from sun preventing it from reaching earths surface and causing sunburns and skin cancer

Question 16

what is the equation for breakdown of ozone by UV rays

Answer 16

O2 —- 2O in an equilibrium steady state

Question 17

how is the equilibrium of ozone breakdown disrupted

Answer 17

human activity in production of CFC ( chlorofluorocarbons)

Question 18

what are CFC used for

Answer 18

refrigerants, air conditioning unit and aerosol propellants

Question 19

why are CFC stable

Answer 19

strong carbon- halogen bonds

Question 20

what happens to CFC at the stratosphere?

Answer 20

CFC break down to form chlorine radicals which catalyse the breakdown of ozone

Question 21

why does the chlorine bond break in CFC

Answer 21

C-Cl bond has the lowest enthalpy so UV radiation provides sufficient energy to break it down by homolytic fission