4- Basics, Hydrocarbons, Alcohols, Haloalkanes, Analysis Flashcards
What is the stem name for one carbon
Meth-
What is the stem name for 2 carbons
Eth-
What is the stem name for 3 carbons
Prop-
What is the stem name for 4 carbons
But-
What is the stem name for 5 carbons
Pent-
What is the stem name for 6 carbons
Hex-
What is the stem name for7 carbons
Hept-
What is the stem name for 8 carbons
Oct -
Stem name for 10 carbons
Dec-
Display formula for butane
CH3CH2CH2CH3
What is the general formula
An algebraic formula that can describe any member of a family of compounds
What is the empirical formula
The simplest whole number ratio of atoms of each element in a compound
What is the molecular formula
The actual number of atoms of each element in a molecule
What is the structural formula
Shows the arrangement of atoms carbon by carbon with the attached hydrogens and functional groups
What is the skeletal formula
Shows the bonds of the carbon skeleton only, with any functional group. The hydrogen and carbon atoms aren’t shown.
What is the display formula
Shows all the atoms are arranged and all the bonds between them
What is a homologous series
An organic compound with the same functional group and similar chemical properties and general formula
Define hydrocarbon
A compound made of hydrogen and carbon atoms only
Define staurated
Has the maximum number of hydrogen atoms possible (around the carbon atom in a hydrocarbon)
Define unsaturated
An organic compound with a double / triple bond capable of adding subsitiuents through addition reactions
Define a functional group
An atom of group of atoms in an organic molecule, that determines its characteristic chemical and physical properties
What do consecutive members of a homologous series differ by
-CH2-
What is the general formula for alkanes.
CnH2n+2
Suffix for alkanes
-ane
Prefix of branched alkanes
Alkyl-
Suffix for alkanes
-ene
Prefix for haloalkanes
Chloro-
Bromo-
Iodo-
Suffix for alcohols
-ol
Suffix for aldehydes
-al
Suffix for ketones
-one
Prefix + suffix for cycloalkanez
Cyclo-….. -ane
Suffix for carboxylic acids
- oic acid
Prefix and suffix for esters
Alkyl-…..-anoate
All organic compounds contain a carbon skeleton - what are the 2 ways this can be
Aromatic or aliphatic
What do aromatic compounds contain
Benzene ring
What ao aliphatic compounds contain
Carbon, hydrogen
How are aliphatic compounds joined together
joined together in straight chains, branched chains or non-aromatic rings
If an aliphatic compound contain a (non aromatic) ring then it can be callled …..
Alicyclic
What are saturated compounds
Only contain carbon-carbon single bonds
What do unsaturated compounds have
Carbon -carbon double bonds, triple bonds or aromatic groups
What is an alkyl group
A fragment of a molecule
What is the general formula for an alkyl group
CnH2n+1
What does rhe main functional group of the molecule usually tell you….
What Homologous series the molecule is in, and gives the prefix or suffix
If there is more than one longest chain when naming organic compounds what do you do
Pick the one with the most side chains
What order do you put the prefix on IUPAC names
In alphabetical order, after the number of the carbon atom each is attached to
If there is more that one identical side chain or functional group. What do you use before that part of the name
2 (di-)
3( tri-)
4 (tetra-)
(Ignor these when factoring the alphabetical order)
When are two molecules isomers of one another
They have the same molecular formula but the atoms are arranged differently
What are the two types of isomers (organic)
Structural isomers
Stereoisomers
What is a structural isomer
The atoms are connected in differnt ways. So although the molecular formula is the same, the structural formula is differnt.
How many differnt types of structural isomers are there
3
What are the 3 types of structural isomers
Chain isomers
positional isomers
Functional group isomers
What is a chain isomer
The carbon skeleton can be arranged differnt, eg. A straight chain or branched in differnt ways
What are the properties like in chain isomers
Similar chemical properties but there physical properties like boiling points will be differnt because of the change in shape of the molecule
What is a positional isomer
The skeleton and rhe functional group could be the same, only with the functional group attached to a differnt carbon atom
Explain the properties in positional isomers
Differnt physicals properties
And the chemical properties might be differnt to
What are functional group isomers
The same atoms can be arranged into differnt functional groups
Explain the properties in functional group isomers
Very differnt physical and chemical properties
How many chain isomers are there with C3H7Br
0
How many positional isomers are there with C3H7Br
What are they
2 isomers
1-bromopropane
2-bromopropane
What are alkanes
saturated hydrocarbons
Every carbon atom has 4 single bonds with other atoms
What is the general formula for alkanes
CnH2n+2
What is the general formula for cyclo….ane
CnH2n
What is the shape of Alkane molecules around each carbon
Tetrahedral
What is the bond angle in alkanes
109.5
What are the boiling points like in alkanes
Smallest alkanes are gases at room temp and pressure as they have got a very low boiling point
larger alkanes are liquids they have a higher boiling points
Explain the difference in boiling points between small and large alkanes
1) alkanes have covalent bonds inside the molecules. Between the molecules there are induces dipole -dipole interactions (London forces) which hold them together
2) the longer the carbon chain,the strong the London forces. This is becuase there’s more surface contact and more electrons to interact with
3)as the molecule get longer it takes more energy to overcome the London forces and the booing points rise
Explain the differnce in boiling points between branches and unbranched alkanes
Branches chains Has a lower boiling points than its straight chain isomer. Branched chain alkanes can’t pack closely together and they have smaller molecular surface areas of contact. However straight chains can pack closely and there is a lot of surface contact between them so the London forces are reduced in branched chains.
If you oxidise (burn) alkanes with oxygen what do you get and what is the name of this reaction
Carbon dioxide and water
Combustion
Combustion equation
Alkane + oxygen = carbon dioxide + water
What do combustion reaction happen between
Gases
So liquid alkanes have to be varporised first
Smaller alkanes turn into gases ………. How else can this be described.
And what does that mean for how easy it will burn
More easy
(There more volatile)
it will burn more easily too
Larger alkanes release more energy per mole beacuse….
Because they have more bonds to react
Why are alkanes food fules
Lots of energy when they burn
All bases at the same temp and pressure have the same……
Molar ratio
How do you use the ratio of the volumes of the gases reaction together to calculate the molar ratio and therefore what hydrocarbon is combusting
1) using volumes provided, write the reaction equation
2) simplify
3) fill in the blanks with with you know. For example if 8 moles of o2 reacted to form 5 mole of carbon dioxide the rest of the mole must end as h20
4) use the final combustion equation to identity x
5) all the carbon atoms from x end up in carbon dioxide molecules and all the hydrogen most end as water
What does burning alkanes in limited oxygen produce
Carbon monoxide
Why is carbon monoxide poisonous
The oxygen in your blood stream is carried around by heamoglobim
Carbon monoxide is better at binding to haemonolobin than oxygen is so it binds to the heamoglobin in your blood stream before oxygen can
Thus means that less oxygen can be carried around your body leading to oxygen deprivation. At high concentrations, carbon monoxide can be fatal
What is an isomer
Molecules with the same molecular formula but differnt structural or spatial arrangementsof the atoms within the molecule
What are the 2 types of isomers
Structural
Sterioisomerism
What is a structural isomer
Same molecular formula but differnt structural formula
What is a position isomer
Molecule stays the same but the position of the functional group changes
Suffix for naming alcohols
Ol
When the alcohol group is not priority what is it called
Hydroxyl group
Where is the functional group on an aldehyde
Always on the terminal c atom ( so we don’t give a numerical position
Ketones suffix
-one
Suffix of haloalkanes
Ane
Alkenes suffering
Ene
What has the lowest priory when naming
Alkane and haloalkes
What has a higher priority in m,wind alchol or alkanes
Alcohol
When there is a alkene and a alcohol functional group how is it written
……… en ……- - ol
What has more priority a functional group or lowest numbers
Functional group
What are the two types of bond fissions
Homolytic
Heterolytic
What is bond fission
Breaking a covalent bond
What is heterolytic fission
In heterolytic fission the bond breaks unevenly with one of the bonded atoms recieving both electrons from the bonded pairs
Two differnt substances are formed - a positively charged cations and a negatively charged anion
What does a Curley arrow show
Movement of an electron pair
What is homolytic fission
The bond breaks evenly and each bonding atom recives one electron from the bonded pair. Two electrically charged ‘radicals’ are formed
What is a radical and how are they shown
A particle that have an unpaired electron
They are shown in mechanisms by a big dot next to the molecular formula (the dot represents the unpaired electron )
Are radicals reactive and why
Very
Because of the unpaired electrons
For which functional groups is it always on carbon 1
Aldehydes
Carboxylic acid
Nitriles
Does a high priority take the suffix or a prefix
Except form what
Suffix and lowest number
Double and triple c-c bonds only take suffic form
What is the order of the highest naming priority
Carboxylic acid > aldehydes > ketones > alcohols > alkenes > haloalkanes
If more than one double bond presents in an alkane , what happens to the name
DIene
TRI
And stem ends in a
What is the prefix for haloalkanes - fluorine
fluoro
What is the prefix for haloalkanes - chlorine
Chloro
What is the prefix for haloalkanes - bromine
Bromo
What is the prefix for haloalkanes - iodine
Iodo
When there are more than 2 OH groups
How does it change the name
Di or tri used
And an e on the stem name
If there is a alcohol and another functional group with a higher priority what is rhe alcohol called as a prefix
Hydroxy
What changed about the name when there are two aldehydes groups
Di
And an e is added to the stem.
What changes about the name when there are two ketones groups
Di
And an e is added to the stem
If there are Carboxylic acid groups on both ends of the chain
What is it called
Dioic acid
Halogens react with alkanes forming …….
Haloalkanes
Halogens react with alkanes in ………….. reactions
Photochemical
What are photochemical reactions starts by
Ultraviolet light
Describe a photochemical reaction
A hydrogen atom is substituted by chlorine or bromine
A hydrogen atom is substituted by chlorine or bromine
What’s is this reaction called
Free radical substitution
What is rhe 3 reaction mechanisms for free radical substitution with chlorine and methane
Initiation reaction
Propagation reactions
Termination reaction
What is initiation reaction
(With Chlorine and methane as an example )
Free radical substitution
1) sunlight provided enough energy. To break the cl-cl bond
This is photodissociation
Cl2 —-> 2cl.
2) the bonds splits equally and each atom gets to keep one electron x homolytic fission
The atoms becomes a highly reactive free radical becasue of its unpaired electron
What is it called when sunlight provids enough energy to break the cl-cl bond
Photodissociation
What is propagation reaction
(With Chlorine and methane as an example )
Free radical substitution
Free radicals are used to and created in a chain reaction
1) cl. Attacks a methane molecule : ch. + ch4 —> .ch3 + hcl
2) the new methyl free radical, , .ch3, can attack another cl2 molecule. : .CH3 + Cl2 —-> CH3Cl + Cl.
3) the new Cl. Can attack another ch4 molecule and so on until all the Cl2 or ch4 molecules are wiped out
What is a termination reaction
(With Chlorine and methane as an example )
Free radical substitution
1) the two free radicals join together, making a mole stable molecule,
2) there are heaps of possible termination reactions. Examples.
Cl. +.CH3 —> CH3CL
.CH3 + .CH3 —> C2H6
Cl. + Cl. —> cl2
What is a problem with free radical substitution
If your trying to make a particular product , you don’t get only the product your after but a mixture of products
General formula for alkenes
Cn H2n
What do au alkenes molecules have
At least one c=c double covalent bond
Are c= c double bonds unsaturated + why
Yes
Because they can make more double bonds with extra atoms in addition reactions
A double bund is made up of what two bonds
Sigma and pi
When is a sigma bond formed
When two s orbitals overlap
Explain what happens when two s orbitals overlap
- They overlap in a straight line.
This gives the highest possible electron density between two nuclei - this is a single covalent bond
The high electron density between the nucleus means there is a strong electrostatic attraction between the nuclei and the shared pair of electrons . This means that sigma bond have a high bond enthalpy
What is the strongest type of covalent bonds
Sigma bond
When is a pi bond formed
sideways overlap of two adjacent p orbitals
Whya have pi bonds got two parts to it
One above and one bellow the molecular axis. This is because the p orbitals which overlap are dumbbell shaped
Why are pi bonds weaker than sigma bonds
Because the electron density is spread out above and below the nuclei. This means that the electrostatic attraction. Between the nuclei and shared pair of electrons. Is weaker so pi bonds have a relatively low bond enthalpy
Are C-C and C-H sigma or pi bonds
Sigma
Why don’t alkanes react easily
Only contain C-C and C-H sigma bonds which have high bond enthalpy and so are difficult to break.
The bonds are non polar do they don’t attract nucleophiles or electrophiles
Why are alkenes more reactive
The C=C bonds contains both sigma and pi bond
The C=C double bond contains four electrons so it has a high electron density and the pi bond also sticks out above and below the rest of the molecule. These two factors means rhe pi bonds is likely to be attacked by electrophiles.
The low bond enthalpy of the pi bond also contributes to the reactivity .
Why are alkenes good starting points for making other organic compounds
Because the double bond is so reactive
What are alkenes good starting points for
Organic compounds and for making petrochemicals
can double bonds rotate
Yes
How are atoms arranged in a C=C double bond
1) Carbon atoms in a C=C double bond and the atoms bonded to these carbons all lie in the same plane (they’re planar).
Because of the way they’re arranged, they’re actually said to be trigonal planar — the atoms attached to each double-bonded carbon are at the corners of an imaginary equilateral triangle.
What are the bond angles in the planar unit
All 120°
Are all alkenes completely planar
In ethene yes
But not in larger alkenes
But the >C=C< unit is still planar
Why can’t C=C atoms around it rotate
Because of the way the p orbitals overlap to form a pi bond
Are double bonds rigid
Yes
Even though atoms can’t rotate about a double bonds, they can still rotate …..
About any single bond in a molecule
The restricted rotation around the C=C double bond is what causes alkenes to form, ……
Stereoisomers
What is a stereoisomers
Have the same structural formula but a differnt arrangement in shape
When do stereoisomers occur
When two double bonded carbon atoms each have two differnt atoms or groups attached to them
What are the names of the stereoisomers
Z-Isomer
E- isomer
What is a Z-isomer
Same group either both above or below the double bond
What is the E-isomer
The same group positioned across the double bond
How Is the E and Z separeated from the name when naming stereoisomers
By a dash
Who came up with the solution to the problem with stereoisomers having totally differnt groups attached
Mr cahn
Mr ingold
Mr prelog
What is the name for the rules used to work out which is E or Z isomers for any alkenes
Cahn-ingold-prolog (CIP) rules
How does CIP rule name E and Z isomers
Looks at the atoms directly bonded to each of the C=C carbon atoms
Atoms with the higher atomic number of each carbon is given the higher priority
You can now assign the isomers as E and Z.
if the 2higher priority groups are positioned across the double bond from one another is the E isomer
If a carbon is directly bonded to two carbon atoms, what do u do when looking if E or Z isomers
you need to go further along the chain to work out ordering
The methyl carbon is only attached to the hydrogen atom but ethyl carbon is attached to another carbon atom so the ethyl group is high priority
What can E/Z isomers also be known as
Cis - trans isomers
of the carbon atoms have at least one group in common then you can call the isomers what …..
Cis or trans
Or
E- or Z-
What does cis means for naming stereoisomerism
The same groups are on the same side of the double bond
What does trans mean in naming stereoisomers
the same groups are on opposite side of the double bond
When does the cis - trans system not work
If the carbon atoms both have totally differnt groups attached to the,
What is an optical isomer
A special kind of stereoisomerism that occurd when there is an asymmetrical carbon with an organic molecule - called a chiral carbon
WHat is a chiral carbon
Carbon with 4 different substituents bonded to the centre carbon atom - so no line of symmetry
Asymmetrical molecules arise due to the chiral carbon what does it give rise to
Two isomers (non-superimposable mirror images)
They are optical isomers
What are the two optical isomers known as
Enatiomers of each other
(Oftern with a + or - depending on how they effect the plan of polarised light)
Each enatiomer of a chiral molecule will rotate the plan of polarises light by …..
90°
+ enantimer - rotates the plane by 90°………..
Clockwise
-enantimer - rotates the plane by 90°………..
Anti-clockwise
If a 50:50 enantiomer split what is it called
Racemic
Aliphatic
Carbon atoms are joined to each other in branched or unbranched chains or non aromatic rings
Alicyclic
Carbon atoms are joined to each other in ring structures
Aromatic
Some or all the atoms are joined in a benzene ring
What is the bonding in alkanes
Bond is the result of the overlap between two orbitals of the bonding atoms ( sigma bonds)
Each carbon atoms have 4 sigma binds
What is the shape of alkanes and the bong angle
Tetrahedral
109.5 °
Why are alkane shapes flexible
The sigma bond lie between the two atoms in a horizontal plane and there is free rotation
Describe of a sigma bond in alkanes
One SP3 orbital form each carbon overlap to form a single c-c bond called a sigma bong
What is this called
1S2 2S2 2p2 ——-> 1s2 2s1 2p3
Hybridisation
How does boiling point change as the carbon chain increases in alkanes
Increases
Why does boiling point increase as chain length of alkanes increase
As chain length increases the molecule will have a larger surface area
This is greater constant between molecules
London forces between molecules are therefore greater
How does branching of alkanes effect boiling points
Branched chain compounds have lower boiling points than the corresponding straight chain isomer
The London forces depend on the surface area of contract, it becomes smaller on account of branching so the boiling point of the branched chain alkenes are less than the straight chain isomers
Are alkanes soluble in non polar substances and why
Yes
They are non polar
They interact and from new London forces overcoming the old ones
Are alkanes soluble in polar solvents and why
No
They are non polar
A lot of energy is required to overcome the hydrogen bonding in water, any interaction of alkane and water will only result in new London forces + this is not energetically equivalent to overcoming the old London forces and hydrogen bonding
What are electrophilic addition reactions
The alkene double bond opens up and atoms are added to the carbon atom
Why do electrophilic addition reactions happen
The double bond has got plenty of electrons and is easily attacked by electrophiles
What are electrophiles
Electron pair acceptors
They are usually shot of electrons so they’re attracted to areas where there are lots of electrons
Give some examples of electrophiles
Positive charged ions
Like H+
And polar molecules
What does adding hydrogen to C=C bond produce
Alkanes
What are the conditions for addinf hydrogen to a C=C double bond to produce an alkane
(Hydrogenation )
Nickel catalyst
150°c
Halogens react with Alkenes to form what
Dihaloalkanes
Describe halogenation
The halogen is added across the double bond. And each of the carbon atoms end up bonded to one halogen atom
What type of reaction is halogenation
Electrophilic addition
Describe the mechanism of halogenation
With bromine and ethene as an example
( how would this be differnt for H-Br)
The double bond repels the electrons in br2 polarising Br-br
Heterolytic fission of Br2. The closer Br gives up the bonding electron to the other br and bonds to the C atom
You get a positively charged carbocation intermediate. The Br- now goes over and bonds to the other c atoms forming 1,2-dibromoethane
H-br aleardy has a permanent dipole so step one isn’t necessary
How can u test for carbon carbon double bonds
Add bromine water
Shake
Colour changes orange to colourless
Why does adding bromine water to an alkene decolourise
Becuase bromine is added across the double bond to form a colourless dibromoalkane
Alkenes can be hydrated by steam to form what
Alcohols
What is the reaction from Alkenes to alcohol called
Hydration
What conditions are needed for hydration reaction
300°c
Pressure 60-70 atm
Solid phosphoric (v)acid catalyst
Is the hydration reaction of Alkenes to Alcohols reversible and what is the reaction yield like
Yes
Low (It’s only around 5% from ethene but u reacted alkene gas can be recycled and up ethene yield to around 95%)
Alkenes undergo addition reactions with hydrogen haldies to form what
Haloalkanes
If hydrogen halides add to an unsymmetrical alkene how many possible products are there
And what does rhe amount of each product depend on
2
How stable the carbocation formed in the middle of reaction is
Are carbocations with more alkyls groups more or less stable and why
More because the alkyl group feeds electrons towards the positive charge. So the more stable carbocations is more likely to form
What is a primary/secondary/tertiray carbocation
Refers the the number of r groups
Primary = 1 r groups
Tertiray = 3 r groups
Order primary , secondary and tertiray carbocations into leats to most stable
Primary
Secondary
Tertiray
How does hydrogen bromine react with propene
1) the secondary carbocation is more stable because it’s got two alkyl groups
This carbocation forms more of the time
2) the primary carbocation is less stable as its only got one alkyl group it forms less oftern
What is rhe markownikoff rule
The major product form addition of a hydrogen halide (HX) to an unsymmetrical alkene is the one where hydrogen adds to the carbon with the most hydrogen already attached
Describe complete combustion
Plentiful supply of O2
Alkanes burn completely
Products = co2 and H2O
Products of complete combustion
CO2 and H2O
Describe incomplete combustion
Limited supply if O2
Less energy released per mole than complete
Leads to C or CO
What are the products of incomplete combustion
C or CO
And water
Why are alkanes good fules
Readily available
Easy to transport
Burn in plentiful supply of O2 without producing toxic products
Highly exothermic when combusted
What are the harms of CO
Highly toxic
Odourless
causes death if accumulated in an enclosed space
Toxic to humans
Why is carbon monoxide toxic to humans
Binds with haemoglobin in RBC to from carboxyhaemoglobin ( a stronger bond than that between oxygen and haemoglobin)
Symptoms of carbon monoxide poisoning
Tension headaches
Dizziness
Nausea
Vomiting
Tiredness
Confusion
Stomach pain
Difficulty breathing
What does rhe % level of carboxyhaemoglobin have to be to indicate severe exposure to carbon monoxide
30%
Treatments of carbon monoxide
Breathing in conc O2 and hyperbaric oxygen therapy
What is another word for carbon
Soot
Why is carbon not a desirable product
Global dimming - carbon particles reflect sunlight back into space
Health - soot can enter body (leads to breathing issues)
The double bond in alkenes can opem up and join together to make long chains called …..?
Polymers
Individual small alkenes are called…. (Before joined together to form polymers)
Monomers
How are monomers joined together to form polymers
Addition polymerisation
How to find the monomer form a polymer
Take the repeating unit and add a double bond
Advantages of synthetic polymers
Very unreactive so food doesn’t react with the PTFE coating on plans, plastic window don’t rot.
What is the problem of polymers being very unreactive
Most polymers arnt biodegradable and so they’re very difficult to dispose of
In the Uk how many tonnes of plastic waste are produced each year
Over 2 million tonnes
What 3 ways can u dispose of water platics
Buried
Reused
Burned
When is plastic generally disposed of in landfill
Used when rhe plastic is
- difficult to separate from other waste
- not in sufficient quantities to make separation financially worthwhile
- too difficult technically to recycle
Why is there a need to reduce landfill as much as possible
Because the amount of waste we generate is become more of a problem
What are many plastics made from
Non renewable
Oil fractions
What are ways to reuse plastics after sorting into differnt types
Some plastic can be recycled by melting and remoulding them
Some plastics can be cracked into monomers, and these can be used as an organic feedstock to make more plastics or other chemicals
What can the heat generated from burning plastics be used to do
Generate electricity
Why does burning plastcis need to be carefully controlled
to reduce toxic gases
(Eg, polymer that contain chlorine produce HCL when burned)
What are waste plastics from, combustion passed through and why
Scrubbers which can neutralise gases such as HCl by allowing them to react with a base
What can biodegradable polymers be made from
Renewable raw materials such as starch ( from maize and other plants) or oil fractions, such as from the hydrocarbon isoprene (2-methyl-1,3-butadiene)
So organisms can digest them
Negative of biodegradable,e polymers
More expensive than the non biodegradable equivalents
Why cant u just put biodegradable polymers in landfill and expect them to perish away
And where would u need to put them
lack of moisture and oxygen
Compost heap - so u would have to collect and separate the biodegradable polymers from non biodegradablepolymers
Give a potential use of biodegrable plastic
Plastic sheeting used to protect plants from the frost can be made from poly(ethene) with starch grains in bedded in it in time the start is broken down by microorganisms and the remaining poly(ethene) crumbles into dust. There is no need to collect dispose of the old sheeting.
What are photodegradable polymers
Polymers that decompose when exposed to sunlight
What is a radical
A species with an unpaired valence electron
What is a mechanism
The steps undergone by a chemical reaction as it is occurring
What is a Nucleophile
A species that donates a pair of electrons
( is attracted to a positivity centre)
What is an Electrophile
A species that accepts a pair electrons
(Electron loving)
What does propagation
(FRS) mean
Intermediate step (s) in a chain of reaction where the product of one reaction will undergo further reactions
Problem pf free radical substitution on longer chains
The substitution could take place anywhere on a longer chain
Giving lots of products alongside the desired product (lowering the yield)
Why is free radical substitution an issue
Chlorofluorocarbons (CFCs) destroy the ozone layer
In the atmosphere Cl-cl binds break (in precedes of Uv light ) by homolytic fission on to from chlorine free radicals
These radicals destroy the ozone layer
Uses of CFCs
Coolants in fridges
Degreasing circuit boards
Propellants in aerosols
Dry cleaning solvents
What is the layers of the atmosphere
+ distance from earth
Exosphere - 400km
Thermosphere - 300km
Mesosphere - 50km
Stratosphere and- 40km
Troposphere - 10km
Between what two layers is the ozone layer
Mesosphere and stratosphere
What are dangers of UV radiation
damages DNA
Chases skin cancer
What UV radiation does the ozone absorb
UV-c and most of UV-B
What is rhe Montreal protocol
In 1987, 24 countries signed up the Montreal protocol to ban uses if CFCs
Alternatives to CFC and why.
HFC- hydrogenfluorocarbons (H,F,C)
No Cl so no ozone depletion potential
Explain initiation of CFc
CFCs rise to the stratosphere
UV light provides energy to break Cl-cl bonds to from Cl. radicals
Cl. Radial,s react to destroy the ……… in a …… reaction
ozone
Chain
How many O3 molecules can one Cl. Radicals destroy
1000
What are the propagation reaction for Cl. Radicals and rhe ozone layer
O3 + Cl. —> o2 + Cl.O
O3 + CL.O—> 2O2 + Cl.
What is the overall reaction for Cl. Radical and the ozone layer
2O3 —> 3 O2
What is thermal cracking
Long chain alkanes are heated to a very high temperature, extremely high pressure for a very short space of time
Conditions of thermal cracking
1000-1200K
70 Atm
Thermal cracking products
Shorter chain alkanes + are rich in alkenes
What is catalytic cracking
Long chain alkanes heated with pressure in the presence of a zeolite catalyst.
conditions of catalytic cracking
800-1000k
1-2 atm
Zeolight catalyst
What is a zeolite catalyst
An acidic mineral which has a honeycomb structure made from aluminium oxide and silicon dioxide
Products of catalytic cracking
Branched alkanes
Cycloalkanes
Aromatic compounds
What is the best way to reduce chances of too many bi products for chlorine and methane
Excess of methane
As there is a greater chance of a chlorine colliding with methane molecule and not a chloromethane
What products from further substitution can u get with Cl and methane
CH2Cl2
cHCl3
ccl4
What is the general formula for alcohol
CnH2n+1OH
What categories can alcohol be fitted into
Primary
Secondary
Tertiary
What does weather alcohol is primary secondary or tertiary depend on
Which carbon atom the - OH group is bonded to
Primary = 1 alkyl group
Secondary - 2 lamely groups
Tertiary = 3 alkyl groups
(From where the OH is connected to the carbon)
Are alcohols generally polar molecules
Yes
Why are alcohols generally polar molecules
Due to the electronegative hydroxyl group which pulls electrons in the C-OH bond away form the carbon atom
d
How do hydrogen bonds arise between alcohols
The electronegative oxygen in the polar hydroxyl group draws electron density away from the hydrogen, giving it a slightly positive charge. Thus positive charge can attract the lone pairs on an oxygen from a neighbouring molecule, forming hydrogen bonds
Are alcohols soluble in water
Small alcohols are but larger alcohols solubility in water decrease
Why are small alcohols soluble in water
When you mix alcohol with water, hydrogen bonds form between -OH and H2O. If it’s a small alcohol hydrogen binding lets it mix freely with water
What are larger alcohols less soluble in water
Most of the molecule is a non polar carbon chain , so there’s less attraction for the polar H2O molecules.
What is the trend in alcohol size and solubility in water
As alcohols increase in size, their solubility in water decreases
Why do alcohols have relatively low volatility compared to non polar compound
As alcohols also from hydrogen bonds with each other,
Hydrogen bonding is the strongest kind of IMF so it gives alcohols relatively low volatility’s
What does low volatiles mean
They don’t evaporate easily into a gas
Alcohols react with compounds containing halide ions in what type of reaction
Substitution reaction
Explain how a haloalkane is formed
Form an alcohol
The hydroxyl group is replaced by the halide
What conditions are needed for alcohols to turn to haloalkanes
Acid catalyst
What is formed when water is eliminated form alcohols
Alkenes
What type of reaction is alcohols to alkenes
Elimination reaction
How is an alcohol turned to an alkene
With an acidic catalyst - either concentrated sulfuric acid or concentrated phosphoric acid. The mixture is then heated
An elimination reaction where water is eliminated is called what
A dehydration reaction
When an alcohol dehydrates it eliminates what
Water
What is rhe water molecule made up from when an alcohol dehydrated to an alkene
And what does this mean for the number of possible alkene products
From rhe hydroxyl group and a hydrogen atom that was bonded to a carbon atom from adjacent to the hydroxyl carbon
2 possible alkene products form one elimination reaction depending on which side the hydroxyl group of the hydrogen is eliminated from (if the alkene product can from E/Z isomers then the product will be a mixture of both isomers)
What is the simplest way to oxidise alcohols
Burn them
Doesn’t take much to set ethanol alight and burn with a pale blue flame.
How is ethanol oxidised
The C-C and C-H bonds are broken as the ethanol is complety oxidised
What are the products of ethanol being complete oxidised and what type of reaction is this
Co2 and water
Combustion
What is rhe equation for the complet oxidation of ethanol
C2H5O + 3O2 —> 2CO2 + 3H2O
What can you do to mildly oxidise alcohols
Oxidising agent acidified dichromate (Vl)
(Cr2O7 2- / H+)
The organe dichromate (Vl) ion is reduced to the …….
Green chromium (lll) ion (Cr 3+)
What are primary alcohols oxidised to
Aldehydes and then to carboxylic acids
What are secondary alcohols oxidised to
Ketones only
What are tertiary alcohols oxidised to
They won’t be oxidised
What are aldehydes and keystones
Carbonyl compounds
What is the functional group for aldehydes and ketones
C=O
What is the general formula for aldehydes and ketones
CnH2nO
What do aldehydes have
Hydrogen and one alkyl group attached to the carbonyl carbon atom
What do ketones have
2 alkyl groups attached to the carbonyl carbon atom
How many times can primary alcohols be oxidised
2 x
How to turn aldehyde into carboxylic acid
Oxidise
(Reflux)
How can you control how far an alcohol is oxidesed
By controlling the reaction conditions
If you gently heat ethanol with potassium dichromate (Vl) solution (an oxiditising agent) and sulfuric acid what should you get,
And if u heat to far as it’s hard to control the amount of heat what do u get
Apple smelling Ethanal (an aldehyde)
Usually oxidised to form vinegar smelling ethanoic acid
How can you just form an aldehyde form a primary alcohol without it oxidising further into a carboxylic acid
You need to get it out of the oxidising solution as soon as it’s formed, you can do this by gently heating excess alcohol with a controlled amount of oxidising agent in distillation apparatus so the aldehyde (which boils at a lower temp than the alcohol) is distilled off immediately.
To produce carboxylic acid the alcohol has to be vigorously oxidised. The alcohol is mixed with excess oxidising agent and heated under reflux
How are secondary alcohols oxides to ketones
Refluxing a secondary alcohol with acidified dichromate (Vl) will produce a ketone
Why cant secondary alcohols be oxidised twice
1st oxidation produced a ketone
Ketones can’t be oxidised easily so even prolonged refluxing won’t produce anything more
Tertiary alcohols don’t react with potassium dichromate (Vl) so the solution stays
Orange
What is the only way to oxidise tertiary alcohols
By burning them
What is a haloalkanes
Am alkane with at least one halogen atom in place of a hydrogen atom
Why is rhe carbon halogen bond polar
Halogens are generally much more electronegative than carbon
The positive carbon in a carbon halogen bond is electron deficient. What does this mean it can be attacked by
A Nucleophile
What is a Nucleophile
An electron pair donor
It could be a negative ion or an atom with a lone pair of electrons. It donated an electron pair to somewhere without enough electrons
OH-, CN- and NH3 are all ………. Whuchreact withhaloalkanes
Nucleophile
T or f
Water is a nuceophile that reacts fast
False it reacts slowly
Haloalkanes can be hydrolysed to …….
Alcohols
Haloalkanes can be hydrolysed to alcohols in what type of reaction
A nucleophilic substitution reaction
Explain how haloalkanes can be hydrolysed to alcohols in a nucleophilic substitution reaction
Use warm aqueous alkali
(Eg, sodium hydroxide or potassium hydroxide or it won’t work)
What is hydrolysis
When water breaks bonds
What is the general equation for haloalkanes to alcohols
R-X + OH- ————- > R-OH + X-
OH- / H20
(Reflux)
What is the mechanism for haloalkes being hydrolysed to alcohols
(With bromoethane as an example)
1) OH-is the Nucleophile which provides a pair of electrons for the positive Carbon
2) the C-Br bond breaks heterolytically- both electrons from the bond are taken by the br-
3) br- falls of as OH- bonds to the carbon
Will water work as a Nucleophile in the haloalkes to alcohols reaction
Yes but slower
What is the general equation for haloalkanes with water to from alcohols
R-X + H2O —> R-OH +H+ + X-
How quickly differnt haloalkanes are hydrolysed depends on what
Bond enthalpy
Weaker carbon halogen bonds break more easily - so they react faster
What has the weakest bond and so hydrolysed rhe fasted in carbon-halogen bonds
Iodoalkanes (the further down the group the weaker bonds) have the weakest bonds so they hydrolyse the fastest
What has the strongest bond and so hydrolysed rhe slowest in carbon-halogen bonds
Fluoroalkanes gave the strongest bonds, so they are the slowest at hydrolysing
How can you compare the reactivity of chloroalkanes, bromoalkanes and iodoalkanes
1) when you mix a haloalkane with water it reacts to from an alcohol
2) If you put silver nitrate solution in the mixture too, the silver ions react with the halide ions as soon as they from, giving a silver halide precipitate
3) to compare the reactivity set up three test tubes each containing a differnt haloalkane, ethanol and silver nitrate solution ( this contains the water)
4) a pale yellow precipitate quickly forms with 2-iodopropane — so iodoalkanes must be the most reactive haloalkanes, bromoalkanss reacts slows than iododalkes to form a cream precipitate , and chloroalkanes form a white precipitate the slowest of all
T or f
CFC are haloalkanes
T
What are CFCs
Chlorofluorocarbons
They contain only chlorine , fluorine and carbon
(All the hydrogens have been replaces)
What are the positives Of CFCS
stable
Volatile
Non flammable
Non toxic
Low bp
Odourless
Why are CFCs so stable
Because of the strength of the carbon- hydrogen bonds
What does ozone in the upper atmosphere acts as
Chemical sunscreen
It absorbs a lot of the ultraviolet racyauion which can cause sunburn or skin cancer
How is ozone formed
Naturally when an oxygen molecule is broken down into two free radicals by UV radiation. The free radicals attack other oxygen molecules forming ozone
O2 - —- —-> O +O - ——— > o2 + O —— > O3
What did scientist discover abiut the ozone layer in 1970z and 1980s
Scientists discovered that the ozone layer above Antarctica was getting thinner -
The ozone over the artic has been found to be thinning too.
These holes in the ozone layer allow more harmfull UV radiation to reach earth.
How are the holes in the ozone layer formed
CFCs in the upper atmosphere absorb UV radiation and split to form chroine free radicals. These free radicals catalyse the destruction of ozone. They destroy ozone molecules and are then regenerated to destroy more ozone. One chlorine atom can destroy 10,000 ozone molecules before it formed a stable compound
Cl. Free facials are catalysts, they react with ozone to from an intermediate (ClO.) and an oxygen molecule
What are the 2 propergation reactions for ozone depletion
Cl. + O3 —> O2 + Clo3 .
ClO. + O — > O2 + Cl.
(The O radical domes form the break down of oxygen by UV radiation )
What is the overall reaction for ozone depletion and what is the catalysts
O3 + O —> 2 O2
Cl. Is rhe catalyst
NO. Free radicals are form what
Nitrogen oxides
What do NO. Free radicals destroy
Ozone
What are nitrogen oxides produced by
Car and aircraft engines and thunderstorms
NO. Free radicals react. With the ozone the same way as chlorine radicals so the equations can be represent by what
R wich represents either Cl. radical or NO. Radical
What are the few premitted uses of CfCs
Medical inhalers
Fire extinguishers
Submarines
What are being used as alternatives to CFCS unrulna a
Safer products are developed
HCFCs and HFCs
Hydrocarbons are also used
Explain the effect of HCFCs on the ozone
They are broken down in the atmosphere in 10-20 years
They still damage rhe ozone later but their effect is much smaller than CFcs
Explain the effects of HFCs in the ozone
HFCs Are also broken down in the atmosphere. Unlike HCFCs they done contain chlorine , so they don’t affect the ozone layer
Negative of HFCs and HCFCs
They are greenhouse gasses
They are 1000 times Worse than CO2
Negative of hydrocarbons as alternatives to CFCs
Greenhouse gases
Nowerdays what do most aerosols been replaced by, many industrial fridges and freezers now use what as coolant gas and what is used to make foamed polymers
Pump spray systems Or use nitrogen as the propellant
Ammonia
Carbon dioxide
Are there still ozone holes
Still form in the spring but are slowest shrinking
various gasses in the atmosphere that contain what molecules that are able to absorb infrared radiation and re-emit them in all directions
And what is thus called
C=O
C-H
O-H
The greenhouse effect
What are rhe main greenhouse gases
Water vapour
Carbon dioxide
MEthane
Over the last 150 years why has there been higher conc of greenhouse gases
Worlds pop had increased
We have become more industrialised - meaning we have been burning fossil fuels, releasing Co2 and chopping down forests which absorb CO2
Also growing more food, and cows and paddy fields release lots of methane
What does high conc of greenhouse gases mean for the earth
More heat being trapped and the earth getting warmer - this is global warming
Global warming is through to be responsible for recent changes to climate - such as the shrinking of the polar ice caps and less predictable weather
What evidence is there of climate change
Evidence shows that earths average temperature has increased dramatically in the last 50 years and that CO2 levels have increased at the same time. The correlation between CO2 and temperature is pretty clear, but just showing the correlation doesn’t prove that one thing causes another..
There is now a consensus and climate scientist at the link is casual
What do climate scientists believe the recent warming is due to
Anthropogenic
(Human activities)
How are government working to reduce their greenhouse gas emissions
Scientific evidence has persuaded governments to form a global agreement that climate change could be damaging for people, the environment and economies and that we should try to limit it
In 1997, the Kyoto protocol was signed- industrialised countries promised to reduce their greenhouse gas emissions to greed levels. The agreement came to an end in 2012 and currently has no replacement though. Many governments agreed that they need to reduce the CO2 emissions by around 50% by 2050.
The UK government has created policies to use more renewable energy supplies, such as wind and solar farms in order to reduce their emissions
Describe how an infrared spectroscopy work
A beam of IR radiation is passed through a sample of a chemical
The IR radiation is absorbed by the covalent bond in the molecules increasing thru vibrational energy
Bonds between differnt atoms absorb differnt frequency’s of IR radiation.
Bonds in differnt placed in a molecule absorb differnt frequencies
What shows as differnt frequencies of IR radiation
Bonds between differ atoms
Bonds in differnt places in a molecule
Where are C-H groups found
Alkyl groups
Alkenes
Adenes
Where are O-H groups found
Alcohols
Carboxylic acids (but thus has a differnt frequency to alcohols due to the bond being in a differnt place)
what does an infrared spectrometer produce
A spectrum that shows what frequencies of radiation the molecules are absorbing
What can you use the spectrum produced by the infrared spectrometer to identify
The functional groups in a molecule
And if a functional group has changed in a reaction
Which way do the peaks on IR spectra Point
Downwards
What is wavenumber
Measure used for frequency on an IR spectrum
How to calculate wavenumber
1/ wavelength in cm
Where do most organic compounds produce a peak at and what causes thus
About 3000 cm -
C-H
What does a strong sharp absorbs ion at 1700 cm-1 show
There’s a c=o group
What do peaks show on an infrared spectrum
Where radiation is being absorbed
How are infrared spectroscopy used in brethalysers and why is it chosen
To work out if a driver is over the drink - drive limit
The amount of ethanol vapour in the drivers breath is found by measuring the intensity of the peak corresponding to the C-H bond in the IR spectrum.
It’s chosen becasue it’s not affected by any water vapour in the breath
Uses of infrared spectroscopy
Breathalyser
Monitoring conc of pollution gases (including, CO, NO, which are both present in car Emissionssj
How can IR spectroscopy be used to monitor conc of polluting gases
The intensity of the leans corresponding to c=- O or N=O can be studied to monitor their levels
what can u work out form mass spectrum
Relative atomic mass
What is a mass spectrum produced by
A mass spectrometer
How do mass spectrometers work
The molecules in a sample are bombarded with electrons which remove an element form the molecule to form a molecular ions, M+(g)
How do you find the relative molecular mass for a mass spectrometer
Look at the molecular ion peak ( the M peak ) the mass change valve of the molecular ion peak is the molecular mass (this is ash ion the ion has a 1+ change which it normally will)
What is on the Y axis is of a mass spectrum
Abundance of ins
What is on the x axis of a mass spectrum
mass/charge ratio
For most organic compounds where is the M peak
The M peak is rhe one with the second highest mass / change ratio
What is the smallest peak to the right of the M peak called
The M+1 peak
What causes the M+1 peak for organic compounds
caused by the presence of the carbon isotope 13C
What does the bombarding of the electrons in mass spectrometry make some of the molecular ions beak up into
Fragments
The fragments that are ions shown up of the mass spectrum making a what pattern
Fragmentation
What are fragmentation patterns use
Use them to identify molecules and their structures
T or f
Only ions show up on the mass spectrum, the ………. Are lost
T
Free radicals
To work out the structural formula from a mass spectrometer , what do you have to work out
What ions could have made each peak form it’s m/z value (you assume the m/z value of a peak matches the mass of the ion that made it )
Even if two compounds contain the same atoms you can still tell them apart with mass Spectrometry.
Why
Because they won’t produce exactly the same set of fragments
T or f
Every compound produces a differnt mass spectrum,
T
What can be used to identify a compound form its spectrum
Large computer databases
What do you do if you are asked to identify a compound form it’s mass or percentage composition, iR spectrum and mass spectrum
1) use the composition to work out the molecular formula of the compound
2) work out what functional groups are in the compound form it’s infrared spectrum
3) use the mass spectrum to work out the structure of the molecule
Organic reactions are slow and substances are usually flammable and volatile
What would happen if you heat them with a Bunsen burner
Evaporate or catch fire before time to react
If you heat an organic with a Bunsen burner they will evaporate and catch fire before you have time to react. how can you get around this problem
Reflux reaction
What is a reflux reaction
Mixture is heated in a flask fitted with a vertical Liebig condenser
- this continuously boils, evaporates and condenses the vapours and recycles them back into thr flask, giving them time to react
How is the heating usually done in a reflux reactjon
Electrical
Hot plates , heating mantles, or electrical controlled water baths
Why are heating usually done electrically for refluxing
To avoid naked flames that might ignite compounds
Why are anti-bumping granules added for refluxing
Added to make boiling smoother
How does distillation work
By gently heating a mixture in a distillation apparatus
The substances will evaporate out of the mixture in order to increase boiling points
What does the thermometer show when doing distillation
Shows the boiling points of the substances that is evaporating at any given time
If you known the boiling point of your pure product, what can you use when doing distillation to tell you when it’s evaporating and therevpfore………….
Thermometer
Condensing
If the product of a reaction has a lower boiling point than the starting material.
Then what can you do
The reaction mixture can be heated so that the product evaporates form the reaction mixture as it forms
If the starting material of distillation has a higher boiling point than the product.
So long as what is controlled it won’t evaporate out of the reaction mixture
Temperature
T or f
Sometimes a product is formed that will go on to react further if it is left in the reaction mixture
T
What can redistillation be used for
If products and irs impurities have differnt boiling points , then redistillation can be used to separate them,
How do you carry out redistillation
Use the same distillation apparatus, but this time your heating and impure product instead of reaction mixture when the liquid you want boils you place a flask at the open end of the condenser ready to collect your product when thermometer shows the temperature is changing put another flask at the end of the condenser because a different liquid is about to be delivered
If the products is insoluble in water, what can you use separation to remove
Any impurities that do dissolve in water, such as salts or water soluble organic compounds
Describe separation
Reaction complete
The mixture is poured into a separating funnel and water is added
The funnel is shaken and then allowed settle. The organic later is less dense than the aqueous layer so should float on top. Any water soluble impurities should have dissolved in the lower aqueous layer. You can them open the stopped on the separating funnel and run of the aqueous layer and collect your product
If you use separation to purify a product, the organic layer will end up with trace amounts of what, so what does it have to be …
Water
Dried
How can you dry an organic layer that has been left after separation
Add anhydrous salt such as magnesium sulfate or calcium chloride. The salt is used as a drying agent - it binds to any water present to become hydrated
When you first ass the salt to the organic layer it will be lumpy. This means you need to add more. You know that all the water has been removed when you swirl the mixturre and it looks like a snow globe
You can filter the mixture to remove the solid drying agent
What does a synthetic route show
How to get from one compound to another
It shows all the reactions with the intermediate products and the reagents needed for each reaction
If you heat a primary alchcok with what reagents under reflect it goes straight to a carboxylic acid
K2Cr2O7
H2SO4
Heat secondary alcohol in reflux apparatus
Conditions for haloalkane to alchcol
Warm NaOH or KOH, H2O reflux
Haloalkane to Alcochol
What can you use to test the C-X bond strengths
H2o
AGNO3
Conditions alcohol to haloalkane
NaX
H2SO4
20°C
Conditions for alcohol to aldehyde
K2Cr2O7
H2SO4
Heat primary alcohol in distillation apparatus
Conditions for aldehyde to carboxylic acid
K2Cr2O7
H2SO4
Reflux
Alcohol to ketone conditions
K2Cr2O7
H2SO4
Heat secondary alcohol in reflux apparatus
Alcohol to alkene conditions
Conc. H2SO4 or H3PO4, hear
Alkene to alcohol Condirions
Steam,
H2SO4 or H3PO4 catalyst,
300°C
60-70 atm
Alkene to Dihaloakene conditions
X2
20°C
Alkene to dihaloalanez
What do you add as X2 to test for in saturation
Br2
Alkene to haloalkane conditions
HX
20°c
Alkene to alkane conditions
H2
Nickel catalyst
150°c
Alkane functional group
C-C
Properties of alkane
Non polar
Unreactive
What typical reaction for alkanes undergo
Radical susbstitution
Alkene to functional group
C=C
Alkene properties
Non polar
Electron rich double bond
Typical reactions for alkenes
Electrophilic addition
Functional group of alcohols
C-OH
Properties of alcohols
Polar C-OH bond
Lone pair on O can act as a nucleophile
Typical reactions of alcohols
Nucleophilic substitution
Dehydration / elimination
Functional group of haloalkane
C-X
Properties of haloalanes
Polar C-X bond
Typical reactions of halo alkenes
Nucleophilic substitution
Aldehyde / ketone functional group C=O
Properties of aldehyde / ketone
Polar C=O bond
Typical reactions of aldehyde / ketones
Aldehydes will oxidise
Carboxylic acid functional group
-COOH
Properties of Carboxylic acid
Electron deficient carbon centre
Typical reactions of carboxylic acid
Esterification
Can a compound have more than one functional group
Yes
What should you include if you are asked how to make one compound for another in an exam
1) any special procedures such as refluxing
2) conditions needed
Bonding in alkenes
No rotation in alkenes around double bond because 2 P-orbitals overlap sideways ( pi bonds)
Describe a pi bond
Very electron dense
In alkenes each carbon only bonded to 3 other atoms
What does thus cause
2p2 hybridisation
Causes a very negative region of space above and below the plane of the polecule
Why is pi bond weaker than sigma
Very negative region of space above and below plane of molecules
Distant from control of nuclei
Physical alkene properties
Each alekene has 2 fewer e- than the corresponding alkane - so similar but alkenes is slightly lower London forces
Mp / bp inc, with nu, of carbon atoms as the strength of London forces increases
Insoluble in water
Why type of reaction turns alkenes in haloalames
Electrophilic addirion reactions
What does electrophillic mean ( basic )
Electron loving
What are polymers
Large molecules built up from small repeating units called monomers
How do polymer come about
Naturally in living things and through chemical processes in industry
What’s the minimum amount of carbons a monomer should have
At least 2 carbons
What does the n mean on a polymer
Number of repeated units
What types of chemical bonding is polymers
Covalent
Uses of poly (ethene)
Most commonly used polymer
Eg, shampoo bottles
Uses of poly(chloroethene)
Pipes
Uses of poly(propane)
Toys
Packing creates
Uses of poly(phenylethene)
Packing material
Food trays
Uses of poly ( tetrafluoroethene)
Coating for non stick pans
Cable insulation
Addition polymers are formed from alkene
What is this called
additition polymerisation
Why are poly(alkenes) unreactive
Strong C-C and C-H bonds
What is the manufacturing process for margarine
Catalytic hydrogenation of unsaturated vegetable oils using hydrogen and nickel catalyst
Liquid vegetable oils are generally polyunsaturated alkenes. Hydrdogenation by reaction of hydrogen using a nickle catalyst converts the double bond to saturated single bonds. Thus increases the melting poking og the oils making it harder and more solid
What does hydration of alkenes mean
Adding water
What is hydration of alkenes a way of marking
Alcohols
What conditions is needed in hydration of alkenes
acid catalyst
Eg, sulphuric acid
What does dehydration of alcohols form by removing what
Alkenes
Removing OH
In dehydration is the less substituted or more substituted alkene more likely to form
More substituted
Do the trans alkenes or cis alkenes form more
So what is it called
(Usually)
Trans
so major
The cis is minor
Are addition polymers polar
No they are non polar
What problems does addition polymers and inert cause
Creates potential environmental problems during disposal
What 2 ways can you dispose addition polymers
Landfill
Burning
Issues with landfill of addition polymers
Long term problems
Non biodegradable so takes many years to break down
Issues with burning addition polymers
Produce toxic fumes
are condensation polymers polar
Yes
How are condensation polymers broken down
Naturally by hydrolysis into their monomer units
Therfore biodegradable and easier to dispose of
What are bioplastics made of
wholly or in part from renewable biomass sources such as sugarcane and corn, or from microbes such as yeast.
Bioplastics made from renewable resources can be …….
be naturally recycled by biological processes, thus limiting the use of fossil fuels and protecting the environment. Therefore, bioplastics are sustainable, largely biodegradable, and biocompatible
Uses of bio plastics
Food packaging, agriculture, compositing bags, hygiene, biomedical products, structural products. Ect
What does biodegradable or compostable mean
can be broken down by microorganisms into water, carbon dioxide, mineral salts and new biomass within a defined period of time.
How quickly something biodegrades depends on what
conditions it’s exposed to
Including temp, duration, presence of microorganisms, nutrients, oxygen and moisture
What a Photodegradable polymers designed to do
degrade when exposed to sunlight in the environment
Uses of Photodegradable polymers
• Plastic waste disposal problems
• Photodegradation of plastic contamination in the marine environment
• Production of photodegradable mulch films with carefully controlled lifetimes.
what 2 steps help products biodegrade
Oxidation
Biodegrading
What 2 ways are there to make plastics photodegradable
Chemists can add a substance that absorbs sunlight to the plastic. The sunlight makes this substance more reactive and it attacks the polymer chains the plastic is made from. When a ‘package’ of light (a photon) hits a molecule of the added substance this molecule helps focus the energy of the sunlight in a way which causes some of the bonds in the polymer to break. The chains become fractured and brittle so the plastic falls apart.
Micro-organisms can attack polythene but only slowly and not if the polythene has a molecular weight greater than about …….
500
Once photodegradable plastic is exposed to light it begins to break down – whether you want it to or not. This can be disastrous if it is mixed with other plastics during recycling.’ Why would this be a disaster?
Photodegradable plastics tend to breakdown in smaller pieces than the smaller pieces will buy the grade if mix, they will most likely be buried in landfill. It is too dark to do this degrading process.
What does solubility mean
A measure of how able a compound dissolves in a given solvent
Why are alcohols soluble in polar solvent s
polar itself
Energy released from new H bonds formed compensate for the energy required to overcome the origional H bonds
Why are longer alcohols less soluble
Most of chain is non polar
So can’t for H bonds
Energetically unfavourable to form new H bonds
What is a dichromate ion
Cr2O7. ^2-
What is the colour change that dichromate ion undergoes when it is reduced
Orange to green
How can you distinguish between an Carboxylic acid and an aldehyde
Add sodium carbonate
Fizzing indicated Carboxylic acid
How do u get from an alcohol to an Carboxylic acid
excess oxidising agent
Primary alcohols oxidation to aldehyde conditions
Dilute H2SO4
K2Cr2O7
Distill
Primary alcohols to Carboxylic acid conditions
Excess K2Cr2O7
Heat under reflux
Dilute H2SO4
Conditions for secondary alcohols to ketone
Dilute H2SO4
K2Cr2O7
Reflux
What is the order of reactivity of alcohols
3°>2°>1°
What is the general equation for halogenation of a tertiary alcohol
R-OH + HX —> R-X + H2O
What type of reaction is halogens and alcohols
Nucelophilic substitution
Why is an acid needed for halogenation of alcohols
Because Oh is a poor leaving group
And O+H2 is a great leaving group
General equation for a secondary and primary alcohol
R-OH + NaX _______H2SO4______> R-X + NaHSO4 + H2O
What is the differnce between the curly arrow mechanism of secondary/ primary and tertiary
Primary and secondary won’t form a carbocation as not stable enough.
Tertiary needs to form a carbocation as otherwise not enough room for substitution
What are the polarity of haloalkanes
Haloalkanes contain a C-X bond
The C-X bond is polar
As hallogens are more electron ene fatigue than carbon
Electronegativity decreases down group 7
What is the solubityly of haloalkanes in water
The bond is not polar enough to dissolve in water
Haloalkes do mix with
………… easily so can be used to clean out stains
Hydrocarbons
Do haloalkanes tend to dissolve in organic solvents, why/why not
Yes
Beacuse the new IMFS have the same strength as the ones being broken in the separate haloalkanes and solvent
Why can haloalkanes undergo nucleophilic substitution
Due to the polarity
So the Bond is attacked by nucleophilws
Examples of nucleophiles
OH-
H2O
NH3
CN
What type of haloalkanes can undergo nucleophilic substitution recation
Primary
What is the strongest
c- halogen bond
And why
C-F
Because F is the smallest halogen and so the sharing of electrons are strongly attracted to the F nucleus
Which C-halogen bond is the most reactive
Iodine
In organic mass spectrum the highest m/z value usually corresponds to?
the molecular ion
And its position provided info on the molecular mass
What are the peaks on mass spectrum from
Fragments
Why do many fragments not show up on on mass spectrum of organic molecules
They are not charged ions
What is the M+1 peak in mass spectrometry of carbon due to ?
Natural abundance of carbon -13
In mass spectrum
the abundance is effected by what
Explain in detail
The stability of the carbocation
The more stable the higher the peaks
The more alkyl groups attached to the carbonation the more stable it is
Why does the mass spectrum of haloalkane oftern show multiple peaks in the molecular ion region
Due to the differnt isotopes of the halogens
What is a common fragment of aldehydes and ketones
Carbon monoxide
Why won’t carbon monoxide fragment not show up on mass spectrum
- but what will it produce
It’s a molecule so uncharged
It will produce a m/z drop of 28 somewhere in the spectrum
Why does the position of the carbonyl group influence the fragmentation pattern
The molecular ion fragments either side of the carbon group
The more stable the acylium ion RCO+ the more abundant it will be
The more abundant the species the taller it’s peak
What can you use mass spectrometry of organic compounds for
Identify molar mass of organic compounds
Gain information about structure
Describe the mass spectrum
Sample vaporised, ionised to form positive ions
Ions accelerated, heavier move slower
Ions detected as mass:charge ratio m/z
As ions reach detector they create a signal which is detected so the greater the abundance the larger the signal
What forms peaks on mass spectrum of organic moelcuels
Fragments of molecules
What is rhe M+ peak formed by in a mass spectrum of organic moelcuels
Ion of the whole molecule
Where do problems with M+ peaks occur on mass spectrum of organic molecules
Problems when elements have a high rate of isotopes
Eg, cl and br
This produce a M+ and an M+2 peak
What peak can carbon-13 produce on a mass spectrum
M+1 peak
What does the amount a bond stretch or bend depend on
Mass of atom and strength of bond
( lighter and stronger bonds is faster
Each chemical bond has a unique natural frequency caused by …..
Vibration in bond
The bonds absorb energy from wavelength of radiation that has ……
The same frequency
On IR - low intensity means that compound has……
Absorbed that frequency
What is the fingerprint region
Below 1500cm-1
It’s unique to every compound
- it’s more difficult to pick out individual bonds
Describe what a carbonyl compound will look like on infrared spectrum,
Sharp and strong absorption around 1700cm-1
Due to c=o bond
Describe what an alcohol will look like on an IR spectrum
Between 3200 and 3600cm-1
Due to O-H bond
Also peak between 1000 and 1300 due to c-o bond
Descirbe what a Carboxylic acid would look like on an IR spectrum
B-road absorption Bayern 2500 and 3300 cm-1
Due to O-H bond
Also strong absoptiom at 1700cm-1 due to C=O bond
Also peak between 1000 and 1300 due to c-o bond
De#curb the infrared spectrophotometer
A beam if infra red radiation passes through sample
A similar beam is passed through the reference cell
The frequency of radiation is varied.
Bond vibrating with a similar frequency absorbs radiation
The amount of radiation absorbed by the sample is compared with the reference
UV absorbed
- what is rhe energy used fro
- and what spectroscopy technique
Movement of electron to higher energy levels
Uv spectroscopy
Infra red absorbed
what is rhe energy used fro
- and what spectroscopy technique
To vibrate bonds
Infra red spectroscopy
Microwaves absorbed
what is rhe energy used fro
- and what spectroscopy technique
To rotate molecules
Microwave spectroscopy
Radio waves absorbed
what is rhe energy used fro
- and what spectroscopy technique
To change nuclear spin
NMR spectroscopy
What are the 3 differnt types of vibrations
Symmetrical stretch
Asymmetrical stretch
Bending
If IR light is passed through the compound
What will is absorb
Some or all of the light at the frequencies at which it’s bonds vibrate
What are wave numbers
Used as a measure of the wavelength of frequency of the absorbtion
What range is IR light absorbed
4000-400
What can the fingerprint region also be checked to see
If a compound is pure
