3.3 Haloalkanes

Question 1

Alkane to Haloalkane

Answer 1

Radical substitution
UV Light
Cl2

Question 2

Haloalkane to alkene

Answer 2

Elimination
Ethanoic NaOH

Question 3

Alkene to haloalkane

Answer 3

Electophillic addition

Question 4

Haloalkane to nitrile

Answer 4

Nucleophilic substitution
Aqueous ethanoic
KCN

Question 5

Haloalkane to amine

Answer 5

Nucleophillic substitution
Excess ammonia (NH3)

Question 6

Haloalkane to alcohol

Answer 6

Nucleophilic substitution
Aqueous NaOH

Question 7

Alcohol to alkene

Answer 7

Elimination
Hot concentrated H2SO4

Question 8

Alkene to alcohol

Answer 8

Electrophillic addition
H2SO4 –> Alkyl hydrogen sulphate
+H2O –> Alcohol

Question 9

Cl

Answer 9

Chlorophyll

Question 10

F

Answer 10

Fluoro

Question 11

Br

Answer 11

Bromo

Question 12

I

Answer 12

Iodo

Question 13

Primary

Answer 13

The C atom bonded to the halogen is only attached to one other C

Question 14

Secondary

Answer 14

The C atom bonded to the halogen is attached to two other C’s

Question 15

Tertiary

Answer 15

The C atom bonded to the halogen is attached to three other C’s

Question 16

Essential condition for free radical substitution

Answer 16

UV light
Provides the energy needed to break the halogen - halogen bond and start the reaction

Question 17

Free - radical

Answer 17

Species with an unpaired electron
species - a thing

Question 18

Mechanism of CH4+Cl2 –> CH3Cl + HCl

Answer 18

Initiation : Cl2 –> 2Cl.
Propagation 1 : Cl. + CH4 –> .CH3 + HCl
Propagation 2 : .CH3 + Cl2 –> CH3Cl + Cl.
Termination : .CH3 + C. –> CH3Cl
2Cl. –> Cl2
2.CH3 –> CH3CH3

Question 19

Initiation

Answer 19

Using UV light to break the halogen - halogen bond to make 2 free radicals

Question 20

Propagation step 1

Answer 20

2 free radicals produced takes a H from alkane
Turns alkane into free radical and a hydrogen halide

Question 21

Propagation step 2

Answer 21

Alkyl radical takes a halogen from a halogen molecule
Forms a haloalkane and reproduces a halogen free-radical

Question 22

Termination

Answer 22

Two free radicals combine

Question 23

What are CFC’s

Answer 23

Haloalkanes with both chlorine and fluorine

Question 24

Ozone breakdown mechanism

Answer 24

I: CCl3F –> Cl. + .CCl2F
P1: Cl. + O3 –> .ClO + O2
P2 : .ClO + O3 –> 2O2 + .Cl

Question 25

Why are CFC’s so damaging to the ozone layer?

Answer 25

Cl. is regenerated in the final propagation causing a chain reaction in the decomposition of the ozone

Question 26

Why does 1,1,1 - trifluoroethane not lead to the depletion of the ozone in the upper atmosphere?

Answer 26

It doesn’t contain Cl
C-F bonds are very strong and don’t break

Question 27

Curly arrows

Answer 27

Double headed show pair of electrons
From bond or lone pair to atom or point where bond is being made

Question 28

Nucleophile

Answer 28

Electron pair donor

Question 29

Nucleophile examples

Answer 29

OH-
CN-
NH3
They all have a lone pair to donate

Question 30

Nucleophilic substitution by OH-

Answer 30

Reagent - NaOH or KOH
Conditions - Aqueous solvent
Product - Alcohol

Question 31

Nucleophilic substitution by CN-

Answer 31

Reagent - CN
Conditions - Water and ethanol solvent
Product - Nitrile

Question 32

Nucleophilic substitution by NH3

Answer 32

Reagent - NH3
Conditions - ethanol solvent, heat and pressure
Product - amine
3 steps

Question 33

Chloropropane with silver nitrate

Answer 33

White / AgCl

Question 34

Bromopropane

Answer 34

Cream / AgBr

Question 35

Iodopropane

Answer 35

Yellow / AgI

Question 36

Weakest bond

Answer 36

C-I
Fastest reaction

Question 37

Strongest bond

Answer 37

C-Cl
Slowest reaction

Question 38

Elimination

Answer 38

Reagent - NaOH or KOH
Conditions - ethanol solvent
Product - alkene
OH- acts as a base
Forms two products - one is usually an E/Z isomer