Module 4 Module 4 Need To Know Flashcards
What is a homologous series (3)
Exam answer
- a series of organic compounds
- with the same functional group
- and each successive member differs by a ch2 group
WHAT IS A RADICAL
A species with an UNPAIRED ELECTRON
Why does boilign point increase as alkyl chain lenght increade
Why decrease with branching
1) as chain increase, the surface contact area is increased
2) this means more and stronger London forces can be made between molecules
3) rewuireijt more energy to overcome thus higher boiling
Branching
1) increased branching reduces surface contact area between molecules
2) this results in less and weaker London forces
3) so boilign lower
Why are alkanes not reactive (2) points spec
1) c and H have similar electronegativitied thus the bond is not polar , very less ( can’t act as electrophiles )
2) c h sigma bond has high bond enthalpy so a lot of energy needed to break for reactions
Explain alkene bonding
What happens to ROTATION a due to Pi bond?
Sigma bond = head on overlap between any orbital
(ED found greatest on line connecting two nuclei)
Pi bond = side in overlap if p orbitals and ED found greatest above and below line connecting both nuclei
2) as there is Ed above and below line, pi bond RESTRICTS rotation of the carbon atoms around the double bond. This means atoms can exist in specific positions in space
Stereoisomer DEFINITON
Same general formula, structural formula but different arrangement of atoms in soace
Remember 2 conditions for Ez
Double bond
- different groups on each atom
REMEMBER WHAT IS CIS TRANS
When two GROUPS THAT ARE THE SAME ARE FOUND ON EACH CARBON (doesn’t have to be hydorgen )
Describe the reactivity of an Alkene (why) 2
More reactive than alkanes
- due to low enthakpy pi bonds (compared to sigma)
- and the fact that pi bonding increases the space available for an electron to be, more exposed, so more reactive
What is NUCLEOPHILE ELECTROPHILE DEFINITION
Nucleophile is an electron pair donator ( negative ions , lone pairs)
ELECTROPHILE is electron pair acceptors (dipoles , positive)
What’s the benefit of having polymers but the downside too
1 good 1 bad major
Making polymers for daily use very cheap, and low reactive so good for food etc
However disposing of them is very hard as they don’t degrade
What are 3 good ways to dispose and make use of polymers and why brief
(Spec)
1) recycling , involving removing toxic from PVC (less waste and made use of it )
2) usign as fuel for combustion ( free energy, saves finite resources )
3) using them as organic feedstock for production of other polymers and chemical processes ( less waste and made use of it)
Why is PVC recycling so IMPORTSNT, what would happen if pvc polymers were used as fuel for combustion
IMPORTANT SPEC POINT WAS IS MADE
PVC contains high chlorine content
When combusted, this produces HYDROGEN CHLORIDE , which is toxic and corrosive
Therefore we need to do PVC recycling to remove hcl formed during this combustion
What’s the benefit of biodegradable and photodegradable polymers
2 BENEFITS SPEC
1) bio degradable are made from biological material, so less stress on FINITE RESORUCES (oil less used)
2) alleviates the problem of disposal of polymers which was hard to dispose of
(Not toxic residue
What are the physical properties of alcohols and why compared to alkanes
- lower volatility / higher boilign point
Due to havign hydrogen bonding in alchol structure as OH is polar, means much more energy needed to overcome these binds as well as London forces, compared to just London for alkanes - high solubility
Due to hydrogen bonds (more energy released when bonding with water)
What happens as the chain of the alchol increases
Compared to alkanes
The effect of increased solubility and increased boiling decreased volatile is seen LESS as rhe OH group takes less effect
What happens to rate of hydrolysis by alklai or whatever down the group
WHY
(2 marks spec)
Rate of hydrolysis INCREASES
- as the bond enthlapy of the carbon halogen DECREASES down the group
How to do PAG to find out the rate of hydrolysis of different halolakanes
1) in one test tube add a certain amount of HALOAKENS and ethanol
- in another add a certain amount of silver nitrate aqueous
2) heat in water bath, and then mix together,
3) start clock, and measure the time taken for colour ti show
Can now compare , the fastest colour to show means the greatest rate of hydrolysis
Explain the PAG to find the rate of hdyroksyidnreallt quickly
What happens
Why ethanol used
Why heat up
NUCLEOPHILIC susbtitiom takes place between halolaken and water found in aqeuous silver nitrate
This then forms precipate with silver
Ethanol is used as haloalkanes are INSOLUBLE in water, so now they can mix and form one layer
Heated up to increase rate of reaction
Benefits of CFCS , why were they used before banned
Very stable due to carbon halogen bond
Means they were good for refrigerants and propellants
Why did scientists end up banning CFCs
1) research
2) consequence
CFCs were banned because research found their stability didn’t last as they reavjed higher parts of atmosphere, and UV light was used to cause initiation and create radicals
These radicals would then catalyse breakdown of the ozone layer , which lead to a ban
2 radicals that catalysed
What’s overall reaction
Halogen radical
NO radical
Both give the same overall equation as O3 +o —> 2 o2 so manipulate
How are NO radicals found
These are found when lighting strikes and in aircraft travel
How to do reflux key points
Heating source
Set up all equipment
- ensure the solution being heated has ANTI BUMPING GRANULES
- try use heat source as heating mantle such that no naked flame should anythign spill (alcohols are flammable)
- make sure the equipment is air tight, use Vaseline or grease or quick fit apparatus
Why do we use anti bumping granules
This is so large bubbles don’t form at bottom of flask and make the glassware vibrate or jump violently
Why water in at bototm
Ensure the jacket is full, and no air bubbles as against gravity
- this makes it colder overall
How to purify
1) use a separating funnel to remove the aqeuos layer after collecting product
- they will have different densities, so add water to the funnel and see which one rises. As a result remove the other layer usign the funnel, or collect the organic layer and use it again
2) id acids used, can remove this by adding sodium cabrinste. Ensure to release pressure usign separating funnel
3) now wash with water, add water again to remove any salts made, and remove aqeuos layer
4) now want to dry the product using drying agent, use CACL2, once clump gone decant into another flask
5) finally redistill this and collect over the TEMPERTAURE required, to remove any last impurities
Impurities could be acid , extra reactant water etc
Main thing tk remember drying agent
calcium chlroide
Remember a fragment ion can be a loss of a hydorgen from an alchol group, don’t lack !
Everything else is just breaks in covalent bonds
When covalent bonds absorb infrared , what happens
The bonds vibrate more as they gain energy
Explain how global warming works
INFRARED ( not uv ) rsdisiom from sun goes through atmospher absorbed and remitted by surfsce and then absorbed and remitted by GREENHOUSE gases in atmosphere, heating up earth
So these covalent bonds absorb air , methane co2 and h2o and re emit back ti earth, heating it up
2 uses of IR SPEC
Spec
Used in breathalysers to detect alcohol
Used to monitor and detect emissions from vehicles
