OCR Module 4.1- Basic concepts and Hydrocarbons

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  • Created by: CBright
  • Created on: 26-02-18 17:23
Homologous series
Families of organic chemicals that have the same functional group and successive members only differ by CH2
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Aliphatic Hydrocarbons
in which the carbon atoms are joined together in either straight chains or branched chains.
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Alicyclic Hydrocarbons
in which the carbon atoms are joined together in a ring structure but are not aromatic.
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Aromatic Hydrocarbons
in which there is at least one benzene ring in the structure
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How do you name branched alkanes?
stem- the longest carbon chain or parent chain, suffix- the most important functional group, prefix- the other functional groups and carbon atoms they are attached to.
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Saturated
only single bonds
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Functional group
a group of atoms that is responsible for the characteristic chemical reactions of a compound.
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Alcohol- formula, prefix and suffix
-OH, hydroxy-, -ol
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Alkane- formula, prefix, suffix
C-C, N/A, -ane
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Aldehyde- formula, prefix, suffix
-CHO, N/A, -al
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Alkene- formula, prefix, suffix
C=C, N/A, -ene
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Carboxylic acid- formla, prefic, suffix
-COOH, N/A, -oic acid
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Haloalkane- formula, prefix, suffix
-F/ -Cl/ -Br/ -I, fluoro-/ chloro-/ bromo-/ iodo, N/A
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Ketone- formula, prefix, suffix
C-CO-C, N/A, -one
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General formula
the simplest algebraic formula for a homologous series
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Displayed formula
shows the relative positions of atoms and the bonds between them
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Structural formula
provides the minimum detail for the arrangement of atoms in a molecule.
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Empirical formula
the smallest whole-number ratio of atoms of the elements in a compound.
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Molecular formula
the numbers and types of atoms in a compound.
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Skeletal formula
a simplified structural formula drawn by removing hydrogen atoms from alkyl chains.
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Unsaturated
contains at least one carbon- carbon double covalent bond.
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Hydrocarbons
compounds that contain only hydrogen and carbon
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Saturated
contains only single covalent bonds
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Isomers
have the same molecular formula but different arrangements of their atoms.
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Structural isomers
compounds with the same molecular formula but different structural formulae.
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Stereoisomers
organic compounds with the same molecular formula and structural formula but different arrangements of atoms in space.
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Cis- trans isomerism
a type of E/Z isomerism in which the two substituent grous attached to both carbon atoms of the C=C bond are the same.
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E/Z isomerism
a type of stereoisomerism caused by restrcted rotation around the double bond- two different groups are attached to both carbon atoms of the C=C double bond.
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What are the Cahn- Ingold- Prelog rules?
1- locate the C=C and redraw it to show the constituents, 2- focus on one C atoms and assign priority to each substituent based on its relative mass. 3- if the high priority groups are on the same side= Z, on different sides= E
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How do you tell which is Cis and which is Trans?
If the two substituents on each Carbon group are the same then E= Trans and Z= Cis.
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Reaction mechanism
models that show the movement of electron pairs during a reaction
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Curly arrows
model the flow of electron pairs during a reaction.
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Homolytic Fission
happens when each bonding atom receives one electron from the bonded pair, forming two radicals.
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What is the general equation for Homolytic Fission?
X-Y --> X' + Y'
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Radicals
species with one or more unpaired electrons
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Heterolytic Fission
happens when on bonding atom recieves both electrons from the bonding pair.
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What is the general equation for Heterolytic Fission?
X-Y --> X+ + Y-
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What bonds are most likely to undergo Heterolytic fission?
Polar bonds
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How do covalent bonds form?
Two radicals or two oppositely charged ions collide.
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Carbocations
very unstable and reactive intermidiates.
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Alkanes
are a homologous series of saturated hydrocarbons
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What is the alkane general formula?
CnH2n+2
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How do alkanes bond?
each covalent bond has direct overlap of the electron clouds from each atom forming a sigma bond.
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What is the bond shape and angle in an alkane?
Tetrahedral shape, bond angle 109.5'
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Are alkane molecules polar or non- polar?
Non- polar
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What are the intermolecular forces between alkane molecules?
Induced Dipol-Dipole interactions or London forces
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How does carbon chain length affect the boiling points of alkanes?
As and alkene molecule gets longer they have more surface area contacts between adjacent molecules. This increases te number of induced dipole-dipole forces. So more energy is needed to overcome these forces and so boiling point increases.
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How does branching affect the boiling points of alkanes?
The more branched a compound is, the fewer surface area interactions there are between molcules. Therefore they have fewer induced dipole-dipole attractions and therefore they take less energy to overcome so decreases boiling points.
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Why do alkanes have low reactivity?
- All the covalent bonds have high enthalpies so a large amout of energy is required to break them. - The carbon-hydrogen sigma bonds have low polarity becuase the electronegativities are almost the same.
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Complete Combustion
oxidising a fuel in a plentiful supply of air.
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What are the outcomes of an alkane undergoing complete combustion?
a clean blue flame, transfers the maximum amount of energy, only carbon dioxide and water are formed.
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Incomplete Combustion
oxidising a fuel in a limited supply of air.
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What are the outcomes of an alkane undergoing incomplete combustion?
cooler dirty yellow flame, as well as carbon dioxide and water it forms carbon and carbon monoxide.
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What condition is needed for radical substitution?
UV light
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What happens during radical substitution?
The halogen undergoes homolytic fission, formin two radicals. A hydrogen atom in the alkane is substituted by a halogen atom.
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What are the 3 stages of radical substitution?
1- Initiation (the formation of the radicals) 2- Propogation (two repeated steps that build up the desired product in a side-reaction) 3- Termination (two radicals collide and make a stable product)
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Alkene
a homologous series of unsaturated hydrocarbons
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What is the general formula of an alkene?
CnH2n
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What is the bonding in alkenes?
A sigma bond is formed between two carbon atoms using the direct overalp of the electron clouds in the two atoms. The pie bond is formed by the electrons in the adjacent p-orbitals overlapping above and below the C atoms.
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What is the shape and bond angle of an alkene molecule?
triagonal planar shape, bong angles of 120'
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What type of isomerism do alkenes primarily show?
Stereoisomerism.
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Why are alkenes more reactive than alkanes?
pie bonds are weaker than sigma bonds and therfore they will break first and react, leaving the sigma bond between the C atoms. The double bond is an area of electronegativity and attracts electrophiles.
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Electrophil
an electron pair acceptor.
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What is hydrogenation?
an addition reaction in which hydrogen is added across a C=C.
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What are the conditions for hydrogenation?
150'C and a nickel catalyst.
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What is halogenation?
an addition reaction where a haogen is added across a C=C to produce a dihaloalkane.
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What can halogenation be used for?
a test for saturation, bromine water will react and saturate the hydrocarbon, making the solution decolourise.
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What is hydration?
an addition reaction between a gaseous alkene and steam- used in industry to make alcohols.
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What are the conditions for hydration?
H3PO4 catalyst, 300'C, 65 atm
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What is the addition of hydrogen halides?
an addition reaction in which a hydrogen halide is added across the C=C.
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What does this produce?
Haloalkanes
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How does this reaction occur?
The hydrgen halides are bubbled through the alkene, causing a reaction.
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What is Markowinoff's rule?
This states that when H-X is added to an unsymetrical alkene, the H becomes attached to the C with the most H atoms to start with, forming the major product. Because carbocations that have alkyl groups attached are more stable than those with H atoms
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Monomers
small molecues that are used to make polymers.
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Polymers
macromolecules made from small repeating units
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Repeating unit
a specific arrangement of atoms that occurs in a structure over and over again
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What happens durng polymerisation?
Monomers have their pie bond broken, the electrons from each pie bond make a sigma bond with a neighbouring carbon on a different monomer.
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How do you deduce polymers from their monomers?
1- draw monomer so C=C is central, 2- draw square bracket around monomer, 3- change C=C to C-C extending bonds through each bracket, 4- add subscript n
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What is landfill?
Large holes are lined to stop any contaminants seeping into the water table. Rubbish is put in them and when full they are capped and landscaped. Conditions become anaerobic and reduces the rate of decomposition the waste does not break down.
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What is combustion? (in relation to poymer waste)
Plastics contain a lot of carbon, theit comustion releases CO2, other toxic gases can be made, plastics have a high calorific value do burn in power stations and the energy used ot drive turbines and generate electricity.
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What is reusing?
When the same product is used several times, eg plastic water bottles.
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What is recycling?
plastics are sorted into different types (expensive and labour intensive), they are cleaned and melted down and reshaped into new products. There are concerns about their quality and toxicity.
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How can polymers be used in organice feedstock?
chemucal reactions can break the polymers up into smaller organic molecules which can be usd in other industrial reactions.
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Biodegradable
materials are affected by the action of microorganisms and environmental conditions, leading to decomposition.
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What are biodegradable polymers?
polymers that break down chemically into harmless, or useful substances.
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How are biodegradable polymers made?
Biodegradable polymers (like plant starch) is added to an addition polymer and given time the starch breaks down, making the polymer chains smaller and the material biodegrades.
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Bioplastic
a material made from a renewable source that is biodegradable.
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What are the concerns with biodegradable polymers?
The small pieces of addition polymer may still be hazards to the ecosystem.
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What are photodegradable polymers?
addition polymers with bonds within their structure that are weakened by absorption of light ot that have an additive that is affected by light.
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How do photodegradable polymers work?
Once the polymer is exposed to light, it begins to break down, this is not possible to stop, however photodegradable plastics in landfill may not be exposed to enough light to break down.
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Other cards in this set

Card 2

Front

Aliphatic Hydrocarbons

Back

in which the carbon atoms are joined together in either straight chains or branched chains.

Card 3

Front

Alicyclic Hydrocarbons

Back

Preview of the front of card 3

Card 4

Front

Aromatic Hydrocarbons

Back

Preview of the front of card 4

Card 5

Front

How do you name branched alkanes?

Back

Preview of the front of card 5
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