Organic molecule reactions

Question 1

Free radical substitution

Answer 1

ALKANE -> HALOALKANE
Initiation: UV light splits Cl2 into 2Cl free radicals

Propagation: Cl free radical reacts with alkane creating HCl and a free radical from the alkane (eg, methyl). Then the alkane free radical reacts with some Cl2 and creates a haloalkane and a chlorine free radical. This causes a chain reaction

Termination: the chain ends when the two possible free radicals react together

Question 2

Nucleophilic substitution

Answer 2

HALOALKANE -> ALCOHOL
The nucleophile is OH- provided by NaOH or H2O. Hydroxide ion donates lone pair to delta positive carbon causing a bond that removes the halogen from the molecule.

Question 3

Secondary alcohol oxidation

Answer 3

ALCOHOL -> KETONE

Oxidised using acidified potassium dichromate to form a ketone

Question 4

Primary alcohol oxidation

Answer 4

ALCOHOL -> ALDEHYDE

Oxidised using acidified potassium dichromate to form an aldehyde

Question 5

Continued primary alcohol oxidation

Answer 5

ALCOHOL -> ALDEHYDE -> CARBOXYLIC ACID

Oxidised using acidified potassium dichromate to form carboxylic acid from an aldehyde

Question 6

Tertiary alcohol oxidation

Answer 6

No reaction

Question 7

Hydration

Answer 7

ALKENE -> ALCOHOL

Add water, breaks double bond and adds H and OH groups. Conditions: 70 atms, 300*c, dil. H3PO4 catalyst

Question 8

Dehydration

Answer 8

ALCOHOL -> ALKENE

Using a conc.H2SO4 catalyst, alcohol is dehydrated into an alkene

Question 9

Electrophilic addiction

Answer 9

ALKENE - > HALOALKANE
The electron pair in the π-bond gives the alkene a space of high electron density, so this is a good place for attack by an electrophile. During the attack, heterolytic bond fission occurs. A bond is created between one carbon and one bromine causing the other carbon to become a carbocation, thus attracting the other bromine.

Question 10

What is heterolytic fission

Answer 10

Where both bonding electrons go to the same atom

Question 11

What is homolytic fission

Answer 11

Where the bonding electrons go to different atoms

Question 12

Elimination reaction

Answer 12

HALOALKANE -> ALKENE

Using alcohol NaOH, a hydrogen and a halide are removed, leaving behind an alkene

Question 13

Polymerisation

Answer 13

MONOMER -> REPEATING UNIT

Question 14

Polypropene uses and properties

Answer 14

Rigid, used in containers and kitchen units

Question 15

Polyphenylethene uses and properties

Answer 15

(polystyrene) used as an insulator when expanded

Question 16

Polychloroethene uses and properties

Answer 16

Flexible insulator for wires and pipes

Question 17

Hydrogenation

Answer 17

ALKENE -> ALKANE

Adding hydrogen breaks the double bond forming an alkane. Nickel catalyst, at 150*c needed

Question 18

Advantages of industrial manufacture of ethanol

Answer 18

Quicker
100% atom economy
Easier to mass produce
No waste products
Continuous

Question 19

Disadvantages of industrial manufacture of ethanol

Answer 19

Negative environmental impact - made from crude oil
Uses energy
Costs of creating necessary conditions

Question 20

Advantages of fermentation

Answer 20

Easier to create necessary conditions
Low energy demand
Renewable stock
Readily available reactant

Question 21

Disadvantages of fermentation

Answer 21

Takes much longer
Capped alcohol % or yeast are killed
CO2 biproduct
Batch production
Less than 100% atom economy

Question 22

Fermentation

Answer 22

Glucose forms alcohol using yeast as an enzyme. Anaerobic conditions, warmth and pH 7 required

Question 23

Conditions for industrial hydration of alkenes to make alcohol

Answer 23

300*c, 60-70atms, phosphoric acid catalyst

Question 24

Esterification

Answer 24

CARBOXYLIC ACID + ALCOHOL -> ESTER

Catalysed with conc. sulphuric acid