organic stuff that I forget lmao - first 8 topics

what is a homologous series and features of one

family of organic compounds with same functional groups but different carbon chain length

same general formula, similar chemical properties

how does E-Z isomerism come around

C=C bond restricted rotation (planar) and each carbon in double bond has 2 different groups attached

what is petroleum and what is a fraction

mixture of alkanes

compounds with similar boiling points

process for fractional distillation

• Crude oil is heated in a furnace

• Mixture of liquid and vapour passes up the column which is hot at the bottom and cooler at the top

• Vapours pass up the column via series of trays containing bubble caps until they arrive at a tray that is sufficiently cool - condense to a liquid

order of fractions

• Refinery gases - fuel on site

• Gasoline/petrol - cars

• Naphtha

• Kerosene/paraffin - jet fuel and lighting

• Diesel oil - lorries and taxis

• Lubricating oil and waxes - candles and engine oil

• Fuel oil - ships, power stations

• Tar/bitumen - roads and roofing

what is cracking and why necessary

breaking C-C bonds in alkanes

Shorter chain alkanes are higher in demand and there is less supply - more economically valuable

Longer chain alkanes cracked to form shorter chain alkanes

Alkenes can be used to make polymers - reactive so valuable

conditions for thermal

• produces high proportion of alkenes

  • Free radical fission

  • Reaction involves heating alkanes to high temperatures 700-1200 K under high pressure, up to 7000 kPa

catalytic cracking

• lower temperature - 720 K and slight/moderate pressure using a zeolite catalyst consisting of silicon dioxide and aluminium oxide

• Zeolites have honeycomb structure with enormous surface area

  • Acidic

• This form of cracking produces motor fuels mainly - products are mostly branched alkanes, cycloalkanes or aromatic compounds

use of alkanes

fuels

what produced by combustion of alkanes

carbon dioxide, carbon monoxide, water vapour = toxic and greenhouse gas

sulfur dioxide = acid rain

nitrogen oxides = acid rain, respiratory issues

carbon particles = asthma/cancer

how NO formed

• Ignition sparks in an engine produce high temps which break the N₂ triple bond

  • N₂ + O₂ -----> 2NO

• only at high temperatures

how to get rid of sulfur impurities

flue gas desulphurisation with CaO or CaCO3

how to get rid of nitrogen oxides and carbon monoxide

• Catalytic converter is a honeycomb made of ceramic material coated with platinum and rhodium metals - catalysts

  • Honeycomb shape provides enormous surface area, polluting gases pass over catalyst and react with each other to form less harmful products

• 2NO + 2CO -----> N₂ + 2CO₂

• 2NO -----> N₂ + O₂

stuff about greenhouse effect/gases

• Carbon dioxide bonds (double bonds) vibrate at IR frequency because they are polar - therefore absorb heat

• IR radiation emitted from earth does not escape atmosphere

carbon neutral = no net emissions of carbon dioxide to the atmosphere

carbon-halogen bond and rate of reaction

C-F most polar as F most electronegative

C-I is weaker than/lower bond enthalpy/breaks easier than C-Br or C-Cl/F

why do nucleophilic substitutions occur

Bromine is more electronegative than carbon

C is partially positive

Lone/electron pair donated to the partially positive carbon

what does OH- act as in elimination

• OH^- ion acts as a base and lone pair donor removing proton from halogenoalkane

what does ozone do

absorbing some of the UV rays from the sun - without this skin cancer would be very common (UV rays damage DNA)

why are CFC’s greenhouse gases and why are C-F fine

CFCs can absorb infrared radiation as the molecule has polar bonds

• C-F bonds do not break in UV light

why did CFC’s continue to be used

what does bonding in alkene involve

Double covalent bond = centre of high electron density

how does electrophilic addition occur

C=C is electron dense area

Br₂ becomes polarised

Delta positive Br is attracted to C=C

major v minor product spiel

• Major product formed via more stable carbocation

• State which one is the more stable and that the major came from that

  • Major product formed from the tertiary carbocation rather than the secondary one

• Greater stability of tertiary carbocation due to greater positive inductive effect of three alkyl/two alkyl groups rather than one

why do alkenes not biodegrade/unreactive

strong non-polar C-C and C-H bonds

not open to attack by nucleophiles

what is PVC and its relevance

• Properties of polymers can be modified by use of plasticiser additives - small molecules that get between polymer chains and force them apart allowing them to slide across each other

  • Makes it more flexible

• PVC (polychloroethene) is rigid enough for use as drainpipes but with plasticiser can make aprons

what is ethanol made via fermentation separated by

fractional distillation and used as biofuel

what is biofuel

• Ethanol is a carbon neutral fuel - releases same amount of carbon dioxide when burnt as was taken in from atmosphere when plants grow and are photosynthesised

  • No net emissions of carbon dioxide to the atmosphere

• Biofuel is a fuel derived or produced from renewable biological sources

  • Photosynthesis - 6CO₂ (g) + 6H₂O (l) -----> C₆H₁₂O₆ (aq) + 6O₂ (g)

  • Fermentation - C₆H₁₂O₆ ---> 2C₂H₅OH + 2CO₂

  • Burning - 2C₂H₅OH + 6O₂ ------> 4CO₂ + 6H₂O

  • 6CO₂ goes in and 6 comes out

pros of biofuel

• Biofuels are cost-effective

• Biofuels are more environmentally friendly than regular fossil fuels

• Biofuels are made from renewable sources, rather than finite, and so will not run out

• Biofuels can be produced in large batches due to fermentation process

cons of biofuel

• Transportation of equipment - releases carbon emissions

• Fossil fuels are used to run the fermentation machinery

• Nitrous oxide is released from fermenters used to grow the crop

• Ethical concerns that there will be too much agricultural land being used for growing crops to make biofuels – this could lead to food scarcity

• Ethical issues including reduced biodiversity and habitat loss due to agricultural land being used for crops

• Other ecological issues, this includes soil erosion, deforestation, fertiliser run-off and more

alcohol to alkene use

monomers for addition polymerisation can be formed without deriving them from crude oil

mass spec stuff

precise masses are different

electron impact ionisation = breaks molecular ion into smaller fragments

high-resolution mass spec = molecular formula found, cannot identify compound

infrared info

If a molecule has polar bonds, it can absorb infrared radiation = greenhouse gas

Use fingerprint region - look for match to known spectrum

optical isomerism info

non-superimposable mirror images = enantiomers

• 4 different substituents are attached to one carbon atom - known as the chiral carbon centre

• Polarised light is passed through two solutions of the same concentration, each contains a different optical isomer of the same substance

• Enantiomers will rotate the plane of light in opposite directions

• One solution will rotate the plane of polarisation through one angle - clockwise = +

• The other solution will rotate the plane of polarisation the other way

why hydride ion only react with aldehydes/queeftones

Hydride ion is a nucleophile which is attracted to delta positive carbon in polar C=O bond

But in alkenes - there is a C=C electron rich area

Repels the hydride ion so no reaction occurs

why KCN and not HCN

• KCN dissociates better than HCN to produce CN- ions

  • Aqueous conditions

• CN- ion is toxic so typically not carried out

why optical isomers form in queeftones/aldehydes

equal chance of attacking the plane from above or below the flat trigonal planar of C=O/planar carbonyl group