Resit Exam Ocr Chemistry Unit 2: Module 2 - Alcohols, Halogenoalkanes And Analysis

Front 1

Alcohols

What are the two ways ethanol can be made?

Back 1

-Hydration of ethene

-Fermentation of sugars

Front 2

Alcohols

Draw the hydration of ethene. Include catalysts.

Back 2

(steam)

Front 3

Alcohols

Describe the conversion rate of the hydration of ethene.

Back 3

The reaction is reversible so the conversion of ethene is incomplete - only 5% of the ethene is converted into ethanol.

Any unreacted gas is recycled and passed through the reactor again.

Overall a 95% conversion rate is achieved.

Front 4

Alcohols

What is done in fermentation?

Back 4

Carbohydrates (sugar or starch) are converted into ethanol and CO2.

Front 5

Alcohols

Draw the fermentation of glucose. Include conditions

Back 5

37 degrees.

Front 6

Alcohols

Explain why a temp of 37 is used.

Back 6

Below 25 = reaction too slow

Above 37 = enzyme used to catalyse the reaction is denatured and loses its efficiency

Front 7

Alcohols

Explain the conversion of this fermentation

Back 7

Ethanol solution produced in this way has a concentration of up to 14% alcohol by volume.

The toxicity of the alcohol limits the concentration of the ethanol that can be made by fermentation. This is because the enzyme ceases to function above an alcohol concentration of 14%.

Front 8

Alcohols

Why is it important that fermentation is carried out in the absence of air?

Back 8

It is anaerobic.

Prevents the oxidation of ethanol to undesirable compounds such as ethanal or ethanoic acid which would affect the flavour.

Front 9

Alcohols

What are the uses of ethanol alcohols?

Back 9

- Alcoholic drinks, perfumes, aftershaves, cleaning fluids, methylated spirits (solvents for removing paint or ink stains, fuel in spirit burners, camping stoves)

-Blended with petroleum to increase octane ratings of fuels

-Methanol is used as a clean-burning fuel - use as an additive in high-performance racing cars.

Front 10

Alcohols

What influences the properties of alcohols?

Back 10

Their ability to form hydrogen bonds between OH groups of neighbouring molecules.

Front 11

Alcohols

Draw the formation of hydrogen bonds between molecules of ethanol.

Back 11

Front 12

Alcohols

Define volatility

Back 12

The ease at which a liquid turns into a gas. Volatility increases as boiling point decreases,

Front 13

Alcohols

Describe the volatility of alcohols

Back 13

The presence of hydrogen bonds means alcohols have a higher boiling point and thus lower volatility than alkanes

Front 14

Alcohols

Describe the solubility of alcohols

Back 14

Alcohols dissolve in water because hydrogen bonds form between the polar OH groups of the alcohol and water molecules

Front 15

Alcohols

What happens to solubility as chain length increases?

Back 15

Solubility decreases because a larger part of the alcohol molecule is made up of a non-polar hydrocarbon chain which does not form hydrogen bonds with water.

Front 16

Alcohols

What is a primary alcohol?

Back 16

An alcohol where the OH is attached to a carbon atom with none/1 alkyl group

Front 17

Alcohols

What is a secondary alcohol?

Back 17

An alcohol where the OH is attached to a carbon atom with 2 alkyl groups

Front 18

Alcohols

What is a tertiary alcohol?

Back 18

An alcohol where the OH is attached to a carbon atom with 3 alkyl groups

Front 19

Alcohols

Write the complete combustion of ethanol.

Back 19

lggl

Front 20

Alcohols

What is the colour change for the oxidation of alcohols with K2CR2O7/H2SO4 ?

Back 20

Orange -> Green

Front 21

Alcohols

Draw the oxidation of a primary alcohol when distilled immediately. Include conditions

Back 21

K2CR2O7/H2SO4

Distil immediately

Front 22

Alcohols

Draw the oxidation of a primary alcohol under reflux.

Back 22

Reflux

H+/K2Cr2O7

Front 23

Alcohols

What is reflux?

Back 23

The continual boiling and condensing of a reaction mixture to ensure that the reaction takes place without the contents of the flask boiling dry.

Front 24

Alcohols

Write the oxidation of a secondary alcohol

Back 24

Reflux

K2Cr2O7/H2SO4

Front 25

Alcohols

What happens when you oxidise tertiary alcohols?

Back 25

Nothing, The oxidising agent remains organge.

Front 26

Alcohols

How is an ester formed?

Back 26

Warming an alcohol with a carboxylic acid in the presence of an acid metal catalyst

Front 27

Alcohols

Define esterification

Back 27

The reaction of an alcohol with a carboxylic acid to produce an ester and water

Front 28

Alcohols

Draw the esterification between propanoic acid and methanol.

Back 28

Front 29

Alcohols

What is the function of esters?

Back 29

-Adhesives and solvents in the chemical industry

- Used to produce food flavourings and perfumes

Front 30

Alcohols

How do you prepare an ester in the lab? (check on spec pls)

Back 30

1) In a boiling tube, add 1cm3 of the carboxylic acid to 1cm3 of the alcohol. Carefully add a few drops of concentrated H2SO4

2) Place the boiling tube in a hot water bath at 80degrees for 5mins

3) Pour the product in a beaker of cold water

4) You will see an oil floating on the surface of the water- this is the sweet smelling ester.

Front 31

Alcohols

Define dehydration

Back 31

An elimination reaction in which water is removed from a saturated molecule to make an unsaturated molecule.

Front 32

Alcohols

What is formed when an alcohol is dehydrated?

Back 32

An alkene + H2O

Front 33

Alcohols

What does dehydration require?

Back 33

An acid catalyst - H2SO4, H3PO4

Front 34

Alcohols

Write the equation for the dehydration of ethanol.

Back 34

Reflux

Heat

Conc H2SO4

Front 35

Alcohols

Draw the dehydration of cyclohexanol.

Back 35

conc H3PO4

Heat

reflux

Front 36

Halogenoalkanes

What is a halogenoalkane?

Back 36

Compound in which a halogen atom has replaced at least one of the hydrogen atoms in an alkane chain

Front 37

Halogenoalkanes

What are/were the uses of Halogenoalkanes ?

Back 37

Refrigerants, aerosol propellants, degreasing agents and dry cleaning solvents.

Used in organic synthesis.

Front 38

Halogenoalkanes

What is the general formula?

Back 38

CnH2n+1X

Front 39

Halogenoalkanes

How are halogenoalkanes polar?

Back 39

The difference in electronegativities of the carbon and halogen bond.

Halogen is more electronegative so the bonded electron pair is attracted more closely to the halogen atom, forming a polar bond.

Front 40

Halogenoalkanes

What happens with electronegativity as you decrease down the halogen groups?

Back 40

It decreases.

Front 41

Halogenoalkanes

What reactions do Halogenoalkanes take part in?

Back 41

Nucleophillic substitution

Front 42

Halogenoalkanes

What are the conditions for the hydrolysis of a Halogenoalkane ?

Back 42

aq NaOH/KOH

Heat

Reflux

Front 43

Halogenoalkanes

Write the equation for the hydrolysis of 1-bromopropane

Back 43

Front 44

Halogenoalkanes

Define hydrolysis

Back 44

A reaction with water/OH- (aq) that breaks a chemical compound into two compounds

Front 45

Halogenoalkanes

Define nucleophillic substitution

Back 45

A type of substitution reaction in which a nucleophile is attracted to an electron deficient centre or atom, where is donates a pair of electrons to form a new covalent bond.

Front 46

Halogenoalkanes

Describe what happens in the nucleophilic substitution reactions of Halogenoalkanes

Back 46

1) The OH- ion has a lone pair of electrons. This is attracted and donated to the electron deficient carbon atom in the halogenoalkane. This is nucleophillic attack.

2) The donation of the elctron pair leads to the formation of a new covalent bond between the oxygen atom of the Oh- ion and the C atom.

3) The C-Halogen bond breaks by heterolytic fission, with both electrons going to the halogen atom, forming a halide ion.

Front 47

Halogenoalkanes

How can you measure the rate of hydrolysis of primary Halogenoalkanes ?

Back 47

-Heat the Halogenoalkane with aq silver nitrate with ethanol.

- water acts as the nucleophile and ethanol is the solvent

- The aq AgNO3 reacts with any halide ions present, forming a ppt of the silver halide

- rate = 1/time taken for ppt to form

Front 48

Halogenoalkanes

Write the hydrolysis of 1-chlorobutane and the precipitate.

Back 48

Ch3Ch2Ch2Ch2Cl (aq) +H2O (l) ---->

Ch3Ch2Ch2Ch2OH (aq) + H+ (aq) + Cl- (aq)

Cl- (aq) + AG+(aq) --> AgCl(s)

Front 49

Halogenoalkanes

What needs to be controlled ?

Back 49

1) Mol of Halogenoalkane

2) chain length of Halogenoalkanes

3) temperature - water bath

Front 50

Halogenoalkanes

Describe the procedure for measuring the rate of hydrolysis of Halogenoalkanes

Back 50

1) Measure each Halogenoalkane into separate test tubes in a waterbath at 50dgs

2) Put a solution of ethanol, water and (aq) AgNO3 into another test tube and put this in the water bath.

3) When they all reach the same temperature, add equal amounts to each Halogenoalkane

4) Time how long it takes for a ppt to form

Front 51

Halogenoalkanes

What are the colours of ppts formed?

Back 51

AgCl -white

AgBr - Cream

AgI - Yellow

Front 52

Halogenoalkanes

What two factors affect the rate of hydrolysis?

Back 52

- POLARITY - C-F is the most polar so the partially positive carbon atom attracts the nucleophile most readily = fastest reaction

-BOND ENTHALPY - C-I is the weakest bond so is broken most easily = fastest reaction

BUT bond enthalpy is more important than polarity, so the rate of hydrolysis increases as you go down the group.

Front 53

Halogenoalkanes

What is PTFE? Show how it is formed

Back 53

Polytetrafluroethene

Front 54

Halogenoalkanes

What are the properties of PTFE?

Back 54

-inert

-resistant to chemical attack

0-heat resistant

- non--stick

- electrical insulant

Front 55

Halogenoalkanes

What causes these properties?

Back 55

The strenth of the C-F bonds.

Front 56

Halogenoalkanes

Draw the formation of PVC

Back 56

Front 57

Halogenoalkanes

What are the uses of PVC?

Back 57

Drainpipes, childrens toys, window frams, sports equipment, packaging

Front 58

Halogenoalkanes

What were the original uses and properties of CFCs?

Back 58

-Unreactive, non-toxic

-Non flammable

-Used as refrigerants, propellants, blowing agents

-Were stable because of the strength of the c-Halogen bond

Front 59

Halogenoalkanes

What were the problems with CFCs?

Back 59

They are only stable until they reach the stratosphere where they break down in the presence of uv light to form chlorine radicals which are thought to catalyse the breakdown of the ozone layer.

The depletion of the ozone layer means it cannot absorb the uv light from the sun, leaving it to reach the lower atmosphere, increasing the prevalence of skin cancer,

Front 60

Halogenoalkanes

What are being used as alternatives to CFCs?

Back 60

Hydrofluorohydrocarbons, HCFCs.

They are non-flammable and non-toxic

BUT they still deplete the ozone layer (but much less)

Front 61

Halogenoalkanes

How do you calculate % yield?

Back 61

% Yield = Amount of product, mol / theoretical amount of product, mol

x100

Front 62

Halogenoalkanes

Why might you not get 100% yield?

Back 62

-Reaction may be at equilibrium or not to completion

-by-products may be formed

-reactants may not be pure

-some reactants/products left in equipment

-separation and purification may lead to loss of product

Front 63

Halogenoalkanes

Calculate the % yield of:

CH3CH2OH + 2[O] -> CH3COOH + H2O

9.2g 4.25g

Back 63

CH3CH2OH = 46 g mol-1

CH3COOH = 60 g mol-1

9.21/46 = 0.2

4.25/60 = 0.0725

ACTUAL/THEORETICAL

0.0725/0.2 x 100 = 36.25 %

Front 64

Halogenoalkanes

What is atom economy?

Back 64

Molecular mass of desired product /

Sum of molecular mass of all products

x100

Front 65

Halogenoalkanes

What is the atom economy of Addition of bromine to propene?

Back 65

100%

Front 66

Halogenoalkanes

CH3CH2Ch2CH2Br + NaOH -> CH3CH2CH2CH2OH (Desired) + NaBr

Back 66

74/176.9 x100 = 41.8%

Front 67

Halogenoalkanes

What reactions have what atom economies?

Back 67

Addition - 100%

Sub/Elim - <100%

Front 68

Analysis

What happens when molecules absorb IR?

Back 68

The absorbed energy makes bonds vibrate with either a stretching or bending motion.

Front 69

Analysis

What affects the frequency at which a bond vibrates?

Back 69

The bond strength, bond length and the mass of each atom involved in the bond

Front 70

Analysis

What are the characteristic absorptions of C=O, OH and COOH

Back 70

C=O - 1750cm-1

OH = broad 3200-3550

COOH = very broad 2500-3300

Front 71

Analysis

What are the uses of mass spec?

Back 71

-Identifies unknown compounds

-Determines the abundance of each isotope in an element

-Gives information of structure and chemical properties of molecules

Front 72

Analysis

What are the real life uses of mass spec?

Back 72

-Steroid detection

-Analysing molecules in space

-Detecting toxic chemicals in contaminated marine life

-monitoring breath of patient's breath during surgery whilst under anaesthetic

Front 73

Analysis

How does mass spec work?

Back 73

It determines the mass of a molecule or isotope by measuring the mass-charge ratio of ions

Front 74

Analysis

Describe the process of mass spec

Back 74

1) Sample is introduced via a sample inlet

2) Sample molecules are converted into ions by an ionisation source, i.e. electron impact, chemical ionisation, lasers etc

3) Ions are propelled into a mass analyser

4) Ions are separated according to their mass-charge ration, i.e. by deflection with a magnetic field

5) Ions are detected, A mass spectrum is generated by a computer

Front 75

Analysis

What is m/z ?

Back 75

M=mass

Z=Charge on ion

Front 76

Analysis

Calculate RAM

Back 76

(78.7x24) + (10.13x25) + (11.17x26) / 100 =

24.32

Front 77

Analysis

What is the molecular ion?

Back 77

M+

The positive ion formed in mass spectroscopy when a molecule loses an electron

Front 78

Analysis

What method ionises a molecule?

Back 78

Electron impact - molecules being tested are bombarded with electrons. An electron is dislodged from a molecule and a +ve ion is formed/

Front 79

Analysis

Write the ionisation of ethanol.

Back 79

C2H5OH + e- ---> C2H5OH+ + 2e-

Front 80

Analysis

What is fragmentation?

Back 80

The process in mass spectrometry that causes a +ve ion to split into pieces, one of which is a positive fragment ion.

The energy from the ionisation causes fragmentation to occur.

Front 81

Analysis

Write a possible fragmentation of ethanol molecular ion

Back 81

C2H5OH+ ---> CH3 + CH2OH+ (fragment ion)

Front 82

Analysis

How do you find the molecular ion?

Back 82

It produces a peak with the highest m/z value

Front 83

Analysis

How can you determine molecular mass from mass spec?

Back 83

m/z of molecular ion = molecular mass

Front 84

Analysis

What are common peaks mz values?

Back 84

CH3 + = 15

C2H5+ = 29

C3H7+ = 43

C4H9+ = 57