2 - Organics

Question 1

Why is Cracking important?

Answer 1

Converts low-demand fractions into higher demand fractions

Makes useful hydrocarbons not normally found in crude oil

Question 2

What are the conditions for thermal cracking?

Answer 2

High temp + pressure

Makes high percentage of small alkenes

Question 3

What are the conditions for catalytic cracking?

Answer 3

High temp + slight pressure + zeolite catalyst
More efficient
Zeoloite catalyst favours the formation of branched and cycloalkanes

Question 4

What are the pollution problems caused by burning hydrocarbons?

Answer 4

Global warming
Water vapour is a greenhouse gas
Carbon monoxide and carbon from incomplete combustion
Sulphur dioxide - acid rain
Nitrogen oxides - acid rain and acidic water and petrochemical smog

Question 5

Ways of reducing pollution from hydrocarbon combustion?

Answer 5

Flue gas desulphurisation

Catalytic converters - converts oxides of nitrogen and CO

Question 6

Describe covalent double bonds.

Answer 6

Sigma - side-on overlap, atomic orbitals between the nuclei
Pi - end on overlap, atomic orbitals above and below
Overlap in two places causes restricted rotation

Question 7

What is E/Z isomerism?

Answer 7

Both hydrogen atoms on the same side of the double bond - Z

Both hydrogen atoms on the opposite side of the double bond - E

Question 8

What is the pi bond in an alkene like?

Answer 8

Area of high electron density and can thus attract electrophiles

Question 9

What is Heterolytic fission?

Answer 9

The breaking of a covalent bond which results in both electrons going to the same atom

Question 10

Describe electrophilic addition of alkene

Answer 10

A hydrogen halide or halogen will be attracted by the double bond causing a bond to form breaking the double bond and leaving a radical nucleophile which bonds to the second un-bonded carbon.

Question 11

Describe hydrogenation

Answer 11

Adding hydrogen to saturate the double bond of an alkene using 200 degrees and a nickel catalyst. (Makes alkane)

Question 12

How is the presence of a double bond detected?

Answer 12

Bromine water that causes a brown to colourless change

Question 13

What is Markownikoff’s rule?

Answer 13

“The more electronegative part of the electrophile will usually attach itself to the more highly substantiated carbon atom”

Question 14

What are the major and minor products of electrophilic addition called?

Answer 14

Markownikoff product and the anti-Markownikoff product

Question 15

What does electrophilic addition of an alkene produce?

Answer 15

Halogeno-alkanes

Question 16

Describe hydration of an alkene

Answer 16

Addition of steam, at 300 degrees, 60 atmospheres and using a phosphoric acid catalyst. It produces an alcohol.

Question 17

Advantages of fermentation

Answer 17

Low-tech process
Not use much energy (35-55 degrees)
Uses sugar cane which is renewable

Question 18

Disadvantages of fermentation

Answer 18

Batch process
Slow process
Unethical

Question 19

Other than fermentation how can ethanol be produced?

Answer 19

hydration of ethene - adding steam at 300 degrees, 60 atmospheres and a Phosphoric acid catalyst

Question 20

Advantages of hydration

Answer 20

Fast process
Continuous process
Produces pure ethanol

Question 21

Disadvantages of hydration

Answer 21

High tech - expensive
Uses a lot of energy
ethene comes from crude oil which is non-renewable

Question 22

What is produced when burning ethanol?

Answer 22

CO2 and H20

Question 23

Describe the elimination of alcohols

Answer 23

Elimination reaction of alcohol. Concentrated phosphoric acid (H3PO4) used to remove water and make an alkene.

Question 24

What does the elimination of alcohols produce?

Answer 24

Alkenes (removal of H2O)

Question 25

What forms when a primary alcohol is mildly oxidised?

Answer 25

aldehyde (anal) (COH)

Question 26

What forms when a secondary alcohol is mildly oxidised?

Answer 26

Ketone (anone) (COC)

Question 27

Why can't tertiary alcohols be oxidised?

Answer 27

No available H atoms

Question 28

What is formed when an aldehyde is further oxidised?

Answer 28

Carboxylic acid as an extra oxygen is added (COOH)

Question 29

What can be used as an oxidising agent?

Answer 29

Concentrated Potassium dichromate

Question 30

What can be used to test for Aldehydes?

Answer 30

Tollens reagent - forms 'Silver Mirror'

Question 31

What is a substitution reaction?

Answer 31

A reaction in which one atom or group of atoms on the organic molecule is directly replaced by another.

Question 32

How are free radicals formed?

Answer 32

homolytic fission - breaking a covalent bond in which one electron goes to each atom

Question 33

What are the three steps and conditions for free radical substitution?

Answer 33

Initiation, Propagation, Termination and UV light required

Question 34

What can be done to make sure the major product is achieved in free radical substitution?

Answer 34

Excess of alkane

Question 35

What does free radical substitution make?

Answer 35

Halogenoalkanes

Question 36

What do halogenoalkanes react with?

Answer 36

Nucleophiles as the C-X bond is slightly positive

Question 37

Describe the reaction of halogenoalkanes and hydroxide ions

Answer 37

Nucleophilic Subsitiution .The hydroxide ion (acting as a nucleophile) attacks the carbon from behind forcing the X atom to leave as an ion. It does this under boiling with reflux with aqueous NaOH or KOH. It makes an alcohol.

Question 38

Describe the reaction of an alkene and H2SO4

Answer 38

Electrophilic of cold concentrated sulphuric acid + then warm and add water. An alcohol is formed. This is hydrolysis.

Question 39

Describe the reaction of halogenoalkanes and cyanide ions (CN-)

Answer 39

Nucleophilic substitution. Boiled under reflux with KCN in aqueous ethanol. The Carbon in the cyanide attacks the carbon. CN- ion attacks carbon and halogen ion is formed. It is a very useful reaction for ascending the homologous series as it increases the number of carbons on the chain.

Question 40

Describe the reaction of halogenoalkanes and ammonia (NH3)

Answer 40

Nucleophilic substitution. Heated with ethanol. Primary amine formed. Halogen ion formed.

Question 41

Describe the elimination of halogenoalkanes

Answer 41

Produces an alkene. Ethanolic solution of KOH used. OH ion attacks hydrogen, forms water. curly arrows go from ion to H to C-C bond to X. Loss of X. Hydroxide ion acts as nucleophile.

Question 42

Describe the rates of reaction for the Halogenoalkanes

Answer 42

Increases down group as halogen atom becomes larger, the C-X bond becomes longer, weaker and easier to break thus reacting more quickly.

Question 43

Describe dehydration.

Answer 43

Elimination reaction of alcohol. Concentrated phosphoric acid (H3PO4) used to remove water and make an alkene.

Question 44

How to make chloroalkane from alcohol? (Chlorination)

Answer 44

Add PCL, HCL produced, misty white fumes, only works with primary and secondary alcohols. For tertiary shake with aqueous HCL, water produced

Question 45

How to make bromoalkane from alcohol? (Bromoalkane)

Answer 45

Warm gently with HBr, makes H20 To make HBr, add KBr to conc H2SO4 KBr + H2SO4 --> KHSO4 + HBr

Question 46

How to make iodoalkane from alcohol? (iodonation)

Answer 46

Reflux with PI3, makes H3PO3 To make PL3, add Red phosphorus to 3 iodines 2P + 3I2 --> 2PI3