Organic Year 12 Flashcards
How to calculate empirical formula
Calculate moles (mass/Mr)
Divide both by smallest number
Make whole numbers (round if close, of .5 multiply both by 2)
Aldehyde suffix and functional group
=O on end of molecule
Suffix -anal
Ketone suffix and functional group
Suffix -one
=O in centre of molecule
What are the three types of structural isomers
Chain
Position
Functional group
What is a chain isomer
Same molecular formula, different displayed
What is a position isomer
Functional group changes place
What is a functional group isomer
Changes functional group eg/ Alkene to cycloalkane
What are the two types of stereo/geometric isomerism
E/z and optical
What is E/Z isomerism
Position of high priority groups either side of c=c, fixed as c=c doesn’t rotate, same side is Z, opposite is E
Does the chain length effect reactivity of FG
No
Does chain length affect physical properties and give example
Yes
Eg/ bigger chain will increase mp as IMFs increase
What does branching do to MP
Reduces it as molecules pack together less well, so VdWs can’t act as strong
Does chain length increase or decrease isomer number
Increase
What is the polarity of alkanes like
Non polar
C and H have similar electro negativities
IMFs are only VDWs
What is the boiling point of alkanes like
Increases with chain length as higher IMFS
Decreases with branches as can’t pack together as close so vdws less effective
What is the solubility of alkanes like
Insoluble in H2O as H2 bonds in water are stronger than VDWS in alkanes
How is crude oil formed
Millions of years ago by plant and animal waste breakdown at high pressure and temp
Forms slowly therefore it is non renewable
What compounds are in crude oil and what effect does this have
Alkanes mostly but also other compounds like sulphur, reacting with air to form SO2, which causes acid rain
How does fractional distillation of crude oil happen
Vapourise crude oil in furnace
Pass into tower, hot at bottom and cold at top
Vapour moves up tower via trays containing bubble caps until they reach tray cooler than boiling point and condense and are piped off as liquid
Tar collects as liquid at bottom
No covalent bonds are broken, only VdWs
Why are alkanes cracked industrially
Short chain alkanes are in demand for fuel
Alkenes are needed to act as chemical feedstock to start reactions
What are the two types of cracking
Industrial
Catalytic
What is thermal cracking
High temp 900 degrees High pressure 70atm No catalyst Forms alkenes and alkanes \+ = no waste as alkenes make polymers -= cost as more energy
What is catalytic cracking
Lower temp 450 degrees
Low pressure 1 atm
Uses zeolite catalyst made of aluminium oxide and silicon
Forms alkanes alkenes cyclic alkanes and branched alkanes
+ less expensive and safer
- catalyst is initially expensive but lasts long time
Name all crude oil pollutants
Carbon monoxide Nitrogen oxides Sulphur dioxide Carbon particulates Unburnt hydrocarbons Carbon dioxide Water vapour
Why is CO bad, how is it formed and what is done to reduce it
Formed from incomplete combustion of alkanes
Bad as inhibits Hb so poisons people
Reduced by catalytic converters I
Why is CO2 bad, how is it formed and what is done to reduce it
Produced by combustion of alkanes
Greenhouse gas
Prevented by reduced fossil fuel use
Why is C particulates bad, how is it formed
Produced by incomplete combustion
Causes respiratory issues, cancer and global dimming
Why are nitrous oxides bad and how are they formed
Formed when hot car (2000 degrees) engines combust fuel and the nitrogen formed reacts with O2 in air
NO further reacts to give NO2, which then forms nitric acid and therefore acid rain which corrodes limestone
Why is SO/SO2 bad, how is it formed and what is done to reduce it
Fossil fuels contain sulphur impurities that form SO2 when burnt
It dissolves in water forming H2SO4 which makes acid rain - deforestation and corrosion of environment
Prevented by removal of SO2 by flue gas desulphurisation
Why is Unburnt hydrocarbons bad, how is it formed and what is done to reduce it
Formed by unburnt fuels
Irritant and greenhouse gas
Reduced. H ensuring proper fuel mix
Why is water vapour a pollutant from crude oil
It acts as a greenhouse gas contributing to climate change
How does SO2 cause acid rain
Reacts with O2 and H2O in air to give H2SO4
What are the two methods of glue gas desulphurisation
SO2 + CaO + 2H2O + 0.5O2 —> CaSO4•2H2O + Co2 SO2 is in the gas CaO is the solid compound used H2O is sprayed O2 comes from air
Other method is to use CaCO3 instead of CaO and H2O forms CaSO4 and CO2
How do catalytic converters work
In all new cars to remove Co2, NO and HCs from exhaust gas mixture
Honeycomb structure coated with platinum, polodium and iridium to give a large surface area
The gas passes over and reacts to form less harmful products
2 Equations to show catalytic converters working
2CO+2NO-> N2 + 2CO2
HCs + NO —> N2 + CO2 + H2O
How does the greenhouse effect work
CO2 and other greenhouse gases trap IR so atmosphere heats up so earth sustains life
With additional ghgs this became too efficient and earth started warming
What is the name of the reaction that forms haloalkanes from alkanes
Free radical substitution
What are the three steps of free radical substitution
Initiation
Propagation
Termination
What is the overall reaction for FRS of CH4 with Cl2
CH4 + Cl2 —> CH3Cl + HCl
What is the Initiation Step for Free radical sub
Cl2 —> 2• Cl
UV
Cl2 absorbs UV and breaks bond, e- are split in the middle so each Cl has lone e-
What is a free radical
Molecule with unpaired electron
Highly reactive
What are the propagation steps in Free radical substitution
Equation example
•Cl + CH4 —> •CH3 + HCl
•CH3 + Cl2 —> •Cl + CH3Cl
Radical and stable on each side
What are termination steps in free radical substitution
Involves two FR from propagation reacting together to give stable molecule
Can be any free radicals
How is the ozone layer breaking down
ChloroFluoroCarbons (CFCs) are forming •Cl from UV reactions in atmosphere, then FR is reacting with O3, braking down the layer
CFCs are found in aerosols and fridge coolants
Propagation steps to show ozone breakdown
- Cl + O3 —> •ClO + O2
* ClO + O3 —> •Cl + 2O2
Why are haloalkanes polar molecules
What happens to polarity going down
Contain polar C-X bond as halogens are electronegative delta - and carbons are delta plus
Polarity decreases going down group and group 7 molecules get less electroneg
What is the solubility of haloalkanes like
Bonds aren’t polar enough to be soluble
No H2 bonding
What is the boiling point of haloalkanes like and what effects it
Increases with chain length
Increases going down halogen group
Both because VDWs get bigger due to molecule getting bigger
Branches reduce Boiling point as can’t compact easily
Always higher than alkanes as higher Mr and more polar
What two factors determines reactivity of C-X bond in haloalkanes and which one is a more important factor
Bond polarity and bond enthalpie
Bond enthalpy is more important as experiments have proved that reactivity increases going down group, just like bond enthalpy shows
How does bond polarity determine C-X reactivity
X is more electroneg than C, so bond is polar, therefore C is electron deficient and can be attacked easily by nucleophiles (electron pair donor)
This would predict that C-F is most reactive as C-F is most polar so C+ has most +ve in C-F out of all halogens, so is most likely to be attacked and react
How does bond enthalpy determine reactivity of C-X bond
C-X bond get weaker going down as atom size increases
so shared e- are further away from nucleus
therefore are broken easier
This would predict that C-F is least reactive as it is the strongest bond, and this is correct
