Haloalkane

Question 1

How to turn alkane to Haloalkane

Answer 1

Free radical substitution
Using UV light/Cl2

Question 2

Haloalkane to Alkene

Answer 2

Elimination - ethanolic NaOH

Question 3

Alkene to Haloalkane

Answer 3

Electrophilic addition

Question 4

Alkene to Alcohol

Answer 4

Elimination
Hot concentration
H2SO4

Question 5

Haloalkane to Alcohol

Answer 5

Nucleophilic substitution
NaOH (aq)

Question 6

Haloalkane to Amine

Answer 6

Nucleophilic Substitution
NH3 excess

Question 7

Haloalkane to Nitrile

Answer 7

Nucleophilic Substitution
KCN
Ethanolic (aq)

Question 8

Essential condition for free radical substitution

Answer 8

UV Light
Provides energy required to break a hydrogen bond and start a reaction

Question 9

Free radical definition

Answer 9

A species with an unpaired electron

Question 10

Describe the initiation step

Answer 10

The halogen molecule splits into 2 free radicals
Breaking the halogen-hydrogen bond is called homolytic bond fission

Question 11

Define Propagation 1 (step 2)

Answer 11

•The free radical produced during initiation takes a H from the alkane
• This turns the alkane into a free radical and also produces a hydrogen halide.

Question 12

Define propagation 2

Answer 12

The alkyl radical produced in step 1 of propagation takes halogen atoms from a halogen molecule (not all were split in initiation)
Forming haloalkane and reproduced the halogen free radical

Question 13

Describe termination

Answer 13

Two free radicals combine

Question 14

To reduce the amount of further substitution you would:

Answer 14

Have an excess of the alkane

Question 15

Rules for Curley arrows

Answer 15

• Double headed arrow represents movement of a pair of electrons
• must start from a bond or a lone pair
• must end at an atom or a point where a bond is being made

Question 16

Define a Nucleophile

Answer 16

An electron pair donor

Question 17

What are the 3 different nucleophiles that react with haloalkanes

Answer 17

OH-
CN-
NH3

Question 18

Method of hydrolysis

Answer 18

1. Place measured sample of each halogenalkane (equal molar amounts) into separate test tubes and place in water bath at 50oC
2. Into another test tube place solution of ethanol, water + aqueous silver nitrate and place in same water bath
3. Once at equal temperature add equal volumes of ethanol mixture and haloalkane solution together
4. Time how long it takes for each precipitate to form

Question 19

Chloropropane precipitate colour, time taken to appear and rate of reaction

Answer 19

White, AgCl - 150secs - 0.066s-1

Question 20

Broom propane ppt colour, time taken to appear and rate of reaction

Answer 20

Cream, AgBr - 90secs - 0.011sec-1

Question 21

Iodopropane ppt colour, time taken to appear and rate of reaction

Answer 21

Yellow, AgI - 60secs - 0.016s-1