Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Chemistry Y1 > FC18: Haloalkanes > Flashcards

FC18: Haloalkanes Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Chemistry flashcards Periodic Table flashcards Chemistry 101 flashcards Organic Chemistry 101 flashcards
1
Q

State 3 ways haloalkanes can be prepared

A

from alkanes (UV light with halogen)
from alkenes (with halogen or hydrogen halide)
from alcohols (sodium halide and concentrated sulfuric acid)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are the conditions for making bromoethane from ethanol and hydrogen bromide

A

sodium bromide, concentrated H2SO4, and heat under reflux

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what does heat under reflux do

A

makes sure no gas is lost

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what does in situ mean

A

situated in the original place (undisturbed)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what does hydrolysis mean

A

a reaction where a covalent bond is broken through the reaction with water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is formed when you hydrolyse bromoethane

A

ethanol and hydrogen bromide

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is a nucleophile

A

electron pair donor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

why is the reaction between bromoethane and water slow? what is used instead

A

because water is a poor nucleophile, so aqueous NaOH is used instead

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is the mechanism in the hydrolysis of haloalkanes

A

nucleophilic substitution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is bond enthalpy

A

the energy needed to break a bond

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what has the highest rate of hydrolysis out of the haloalkanes, with chlorine, bromine, iodine

A

the C-I bond has the lowest bond enthalpy, so the activation energy for the hydrolysis of the iodoalkane will be the lowest and the rate of hydrolysis for the iodoalkane will be highest

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

write out the experiment to compare the rate of hydrolysis of different haloalkanes

A

Add aqueous silver nitrate to the haloalkanes dissolved in ethanol
Place into a water bath to maintain the same temperature

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

why is ethanol used in the experiment to compare the rate of hydrolysis of different haloalkanes

A

it is a solvent for both partly non-polar haloalkanes and ionic AgNO3
it dissolves the ionic AgNO3 via ion-dipole bonds and the partly non-polar haloalkane via London forces. Ethanol can also form H-bonding with water

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is formed and write the equations when you carry out the experiment to measure the rate of hydrolysis of bromopropane

A

bromopropane + water -> propanol + H+ + Br- (HBr)
Ag+ + Br- -> AgBr (cream precipitate)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

why are bromide ions produced faster from the hydrolysis of the bromoalkane than chloride ions from the chloroalkane

A

because of the smaller bond enthalpy for the C-Br bond than the C-Cl bond

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are CFCs short for

A

Chloro-fluoro-carbons

17
Q

what are CFCs

A

a group of haloalkanes that were used as refrigerants, solvents, and aerosol propellants

18
Q

What is ozone and how does it form, write the equation

A

ozone is an allotrope of oxygen that forms naturally in the upper atmosphere from O2 under U.V. light
2O2 <->O3 + O (diradical)

19
Q

what is a diradical

A

2 unpaired electrons

20
Q
A
21
Q

why do Cl· radicals form when CFCs breakdown under U.V. light and not F·

A

Because C-Cl bonds have lower bond enthalpy than C-F bonds

22
Q

what is one of the nitrogen oxides formed by the reaction between nitrogen and oxygen and what can it do

A

NO - a radical that can catalyse the breakdown of O3

23
Q

How does nitrogen monoxide catalyse the breakdown of ozone, write any necessary equations

A

·NO + O3 -> ·NO2 + O2
·NO2 + O -> ·NO + O2
overall equation:
O3 + O -> 2O2

24
Q

how do ·NO radicals and Cl· radicals act as catalysts in the breakdown of ozone

A

they are used up in the first reaction and regenerated in second reaction, and so this is a chain reaction

25
Q

what is the Montreal Protocol

A

a global agreement to phase out the production and use of ozone-depleting CFCs

26
Q

Why is the ozone layer in the upper atmosphere so important

A

protects us from harmful U.V. light

27
Q

what are the colours of chloroalkane, bromoalkane, and iodoalkane precipitates

A

white, cream, yellow respectively would form from a colourless solution

28
Q

How can you prepare a haloalkane from alkanes, name the mechanism and conditions

A

halogenation of alkanes
alkane + halogen -> haloalkane + hydrogen halide
radical substitution reaction
U.V. light

29
Q

How can you prepare a haloalkane from alkenes, name the mechanism and conditions

A

alkene + halogen or halogen halide -> haloalkane
electrophilic addition reaction
minor and major product (carbocation intermediates)

29
Q

How can you prepare a haloalkane from alochols, name the mechanism and conditions

A

alcohol + hydrogen halide -> haloalkane + water
mechanism = substitution reaction
conditions = Sodium halide, concentrated sulfuric acid, heat under reflux

30
Q

what type of fission is involved in hydrolysis of haloalkanes

A

homolytic as it forms radicals

Chemistry Y1 (25 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions