as organic

Question 1

Order of priority highest first for naming functional groups :

Answer 1

Carboxylic acids>aldehydes>ketones>alcohols>alkenes>halogenoalkanes

Question 2

where will a curly arrow always start from

Answer 2

a lone pair of electrons or the centre of a bond

Question 3

how does priority grp work w E-Z isomerism

Answer 3

The atom with the bigger atomic number is classed as the priority atom

Question 4

fractional distillation method

Answer 4

• Oil is pre-heated
• then passed into column.
• The fractions condense at different heights
• The temperature of column decreases upwards
• The separation depends on boiling point.
• Boiling point depends on size of molecules.
• The larger the molecule the larger the van der waals forces
• Similar molecules (size, bp, mass) condense together
• Small molecules condense at the top at lower temperatures
• and big molecules condense at the bottom at higher temperatures.

Question 5

Cracking?

Answer 5

conversion of large hydrocarbons to smaller hydrocarbon molecules by breakage of C-C bonds

Question 6

Economic reasons for cracking 3

Answer 6

• The petroleum fractions with shorter C chains (e.g. petrol and naphtha) are in more demand than larger fractions.
• To make use of excess larger hydrocarbons and to supply demand for shorter ones, longer hydrocarbons are cracked.
• The products of cracking are more valuable than the starting materials (e.g. ethene used to make poly(ethene), branched alkanes for motor fuels, etc.)

Question 7

Thermal Cracking

Answer 7

• High pressure (7000 kPa)
• High temperature (400°C to 900°C
• produces mostly alkenes e.g. ethene used for making polymers and ethanol
• sometimes produces hydrogen used in the Haber Process and in margarine manufacture.

Question 8

Catalytic Cracking

Answer 8

Slight or moderate pressure High temperature (450°C)
Zeolite catalyst
Produces branched and cyclic alkanes and aromatic hydrocarbons

Question 9

why is catalytic preferred to thermal

Answer 9

Branched and cyclic hydrocarbons burn more cleanly and are used to give fuels a higher octane number
Cheaper than thermal cracking because it saves energy as lower temperatures and pressures are used

Question 10

how do NOx form

Answer 10

Nitrogen oxides form from the reaction between N2 and O2 inside the car engine.
The high temperature and spark in the engine provides sufficient energy to break strong N2 bond

Question 11

NOx consequence

Answer 11

NO is toxic and can form acidic gas NO2 NO2 is toxic and acidic and forms acid rain

Question 12

CO consequence

Answer 12

toxic

Question 13

CO2 consequence

Answer 13

global warming

Question 14

unburnt hydrocarbons

Answer 14

smog

Question 15

soot

Answer 15

global dimming + respiratory problems

Question 16

catalytic converters structure

Answer 16

Converters have a ceramic honeycomb coated with a thin layer of catalyst metals platinum, palladium, rhodium – to give a large surface area.

Question 17

why do alkanes not react w many reagents

Answer 17

This is because the C-C bond and the C-H bond are relatively strong

Question 18

what do the rate of NS reactions depend on

Answer 18

the strength of the C-X bond
The weaker the bond, the easier it is to break and the faster the reaction.
The iodoalkanes are the fastest to substitute and the fluoroalkanes are the slowest. The strength of the C-F bond is such that fluoroalkanes are very unreactive

Question 19

what does 1’ halogenoalkane tend towards and what does 3’ tend towards?

Answer 19

• Primary tends towards substitution
• Tertiary tends towards elimination

Question 19

ozone decomp mechanism

Answer 19

Cl.+ O3  ClO.+ O2
ClO.+O3 2O2 +Cl.
Overall equation
2O3 3O2

Question 20

why is ozone beneficial

Answer 20

it filters out much of the sun’s harmful UV radiation.

Question 21

why Man-made chlorofluorocarbons (CFC’s) caused a hole to form in the ozone layer.

Answer 21

Chlorine radicals are formed in the upper atmosphere when energy from ultra-violet radiation causes C–Cl bonds in chlorofluorocarbons (CFCs) to break.
The chlorine free radical atoms catalyse the decomposition of ozone, due to these reactions, because they are regenerated. (They provide an alternative route with a lower activation energy)
These reactions contributed to the formation of a hole in the ozone layer.

Question 22

alternative chlorine-free compounds to cfcs

Answer 22

HFCs (Hydro fluoro carbons) e.g. CH2FCF3 are now used for refrigerators and air-conditioners. These are safer as they do not contain the C-Cl bond.
The C-F bond is stronger than the C-Cl bond and is not affected by UV.

Question 23

what does the C=C bond consist of

Answer 23

one sigma (σ) bond and one pi (π) bond.

Question 24

why r alkenes vulnerable to attack by electrophiles

Answer 24

π bonds are exposed and have high electron density. They are therefore vulnerable to attack by species which ‘like’ electrons: these species are called electrophiles

Question 25

Electrophile

Answer 25

electron pair acceptor

Question 26

Direct industrial hydration of alkenes to form alcohols

Answer 26

Essential conditions High temperature 300 to 600°C High pressure 70 atm Catalyst: concentrated H3PO4

Question 27

poly(chloroethene)/PVC = uses

Answer 27

a polymer that is water proof, an electrical insulator and doesn’t react with acids. In its pure form it is a rigid plastic due to the strong intermolecular bonding between polymer chains prevents them moving over each other. In this un-plasticised form it is used make uPVC window frame coverings and guttering. If a plasticiser is added the intermolecular forces are weakened which allows the chains to move more easily, resulting in more flexibility in the polymer. In this form PVC is used to make insulation on electrical wires, and waterproof clothing.

Question 28

alcohol BP

Answer 28

The alcohols have relatively low volatility and high boiling points due to their ability to form hydrogen bond between alcohol molecules.

Question 29

Tertiary alcohols cannot be oxidised at all by potassium dichromate: why

Answer 29

Tertiary alcohols cannot be oxidised at all by potassium dichromate: This is because there is no hydrogen atom bonded to the carbon with the -OH group

Question 29

alc -> alkene

Answer 29

Reagents: Concentrated sulfuric or phosphoric acids Conditions: warm (under reflux) Role of reagent: dehydrating agent/catalyst Type of reaction: acid catalysed elimination

Question 30

2 methods for ethanol production

Answer 30

fermentation from ethene

Question 31

adv + disadvantage of fermentation

Answer 31

Advantages *sugar is a renewable resource *production uses low level technology / cheap equipment Disadvantages *batch process which is slow and gives high production costs *ethanol made is not pure and needs purifying by fractional distillation *depletes land used for growing food crops

Question 32

adv + disadvantage of ethanol production from ethene

Answer 32

Advantages: *faster reaction *purer product *continuous process (which means cheaper manpower) Disadvantages: *high technology equipment needed (expensive initial costs) *ethene is non-renewable resource (will become more expensive when raw materials run out) *high energy costs for pumping to produce high pressures

Question 33

ethanol production from fermentation

Answer 33

glucoseethanol + carbon dioxide C6H12O6  2 CH3CH2OH + 2 CO2 The conditions needed are: *Yeast *No air *temperatures 30 –40oC Type of reaction: Fermentation The optimum temperature for fermentation is around 38oC At lower temperatures the reaction is too slow. At higher temperatures the yeast dies and the enzymes denature. Fermentation is done in an absence of air because the presence of air can cause extra reactions to occur. It oxidises the ethanol produced to ethanoic acid (vinegar).

Question 34

ethanol production from ethene

Answer 34

From ethene Reagent: ETHENE - from cracking of fractions from distilled crude oil CH2=CH2 (g) + H2O (g) CH3CH2OH (l) Type of reaction: Hydration/addition Definition: Hydration is the addition of water to a molecule Essential Conditions high temperature 300 °C high pressure 70 atm strong acidic catalyst of conc H3PO4

Question 35

Where else could CO2 be released - use of ethanol as biofuel

Answer 35

This does not take into account any energy needed to irrigate plants, fractionally distil the ethanol from the reaction mixture or process the fuel. If the energy for these processes comes from fossil fuels then the ethanol produced is not carbon neutral.

Question 36

what is high resolution mass spectrometry, why is it good

Answer 36

High resolution mass spectroscopy can measure the mass to 5 d.p. This can help differentiate between compounds that appear to have similar Mr (to the nearest whole number)

Question 37

If a compound contains a chlorine or a bromine atom then two molecular ion peaks will occur

Answer 37

a M and a M+2 peak will occur due to the two naturally occurring isotopes of chlorine or bromine.

Question 38

difference between OH acid and alcohol peak in IR spectrums

Answer 38

acid = WIDE alc = SHARP