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50 Cards in this Set
- Front
- Back
- 3rd side (hint)
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What are sigma bonds? |
They are the single covalent bonds between C-C or C-H firmed from the overlap of orbitals directly between the bonding atoms Sigma bonds can freely rotate |
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What is the general formula for an alkane? |
CnH2n+2 |
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What are he shapes of alkane like? |
Well because each carbon is surrounded by 4 bonding pairs of electrons, these bonding pairs repel ecahother as far as possible creating a bonding angle of 109.5° (tetrahedral shape) around each carbon atom |
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What happens to the BP as chain length increases? |
It also increases because there are more electron and more points of contact between molecules. So more strong London forces that are harder to break |
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What happens to the BP as alkane branching increases? |
The bp's decrease as increased branching leads to fewer points of contact be teen the molecules. So the London forces become weaker |
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Are alkane soluble? |
Nope. Alkane are non polar and do not dissolve with polar solvents like water. But they do mix with non polar solvents |
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Are alkane reactive? |
Nope. They have a low reactivity because sigma bonds are hard to break |
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What does the complete combustion of alkane form? |
Carbon dioxide and water |
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What does the incomplete combustion of alkane form? |
Carbon monoxide and water |
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What is free radical substitution? |
It is a process where alkane can be made to react with halogens |
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What are the conditions needed for free radical substitution? |
Ultraviolet radiation and a high temperature |
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What are 3 steps of free radical substitution? |
Initiation - forming 2 radicals from the halogen Propogation - reactions between the radicals and the compound Termination - when 2 radicals react together to dorm a new molecule |
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Why does radical substitution have limitations for organic synthesis? |
A large mixture of products are formed that are hard to separate |
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What are alkenes? |
They contain the C=C functional group - unsaturated hydrocarbons |
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What causes a pi bond? |
The sideways overlap of adjacent p orbitals above and below the bonding C atoms. |
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What's bad about pi bonding? |
The bond prevents the rotation around the around the C=C bond |
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What causes a trigonal planar shape around carbon to carbon double Bond |
Well there are three regions of electron density around each carbon atom ( double bond, two single bonds). the three regions of electron density repel each other as far apart as possible to firm a trginal planar shape with the bond angle of 120° |
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why are alkenes much more reactive than alkanes |
Because the pi Bond introduces a region of high electron density above and below the bonding carbon atoms. electrophiles can react with this |
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Stereoisomer |
Have the same structural formula but different arrangements of the atoms in space |
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What are the conditions needed for hydrogenation |
A nickel Catalyst and 150 degrees |
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Four types of addition reactions |
Addition of hydrogen, halogens, hydrogen halides and steam |
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What are the conditions for reacting an alkene with Steam |
An acid catalyst such as phosphoric acid or sulfuric acid... and very high temperatures and pressures |
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What is an electrophile |
A species that can accept a pair of electrons to form a new covalent bond |
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What's a reaction mechanism |
A series of steps that show just how a reaction takes place |
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What is a carbocation |
A positively charged species with the positive charge on a carbon atom |
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What does Markownicoff's rule state? |
That when an electrophoresis H-X reacts with an unsymmetrical alkene, the H atoms of H-X attaches to the carbon with the greater number of H atoms |
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What is addition polymerisation |
Where lots of alkene molecules (monomers) are joined together |
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What is bad about addition polymers |
They're unreactive and nonbiodegradable persisting for long periods of time and causing environmental problems |
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How are addition polymers dealt with? |
They can be recycled which means that they are collected, sorted and processed into new polymers. They can be used as energy production when burnt to generate electricity They can be used as chemical feedstocks for the production of plastics and other organic products |
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What is bad about combusting halogenated Plastics like PVC |
They form toxic waste products like hydrochloric gas which must be removed to prevent discharge into the environment |
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What are biodegradable polymers |
Plant based polymers that break down naturally to form carbon dioxide, water and biological compounds |
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What are photodegradable polymers |
These are polymers that are biodegradable... containing bonds that weaken in the presence of light, initiating their breakdown |
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Is there conditions for when you add a hydrogen halide to an alkene |
Halogen halides a gas at room temperature and are bubbles liquid alkenes to produce haloalkanes |
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How do you produce alcohol from an alkene |
You add steam to an alkene and high-temperature pressure in the presence of phosphoric acid catalyst. this is known as hydration |
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How does chain length affect boiling point of alkanes |
With a longer chain length still more points of interaction between molecules and therefore the London forces are stronger and require more energy to be overcome |
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What is heterolytic fission |
Where the bond breaks unevenly and forms two ions |
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Explain the solubility of alkanes |
Alkenes are usually not soluble in polar solvents like water because they are non-polar themselves. However they will mix with non polar solvents |
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Why do alkanes have a low reactivity |
Because the carbon to carbon and the carbon to hydrogen sigma bonds are strong and hard to break. Also the carbon to carbon carbon to hydrogen bonds and nonpolar. |
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What is needed for the halogenation of alkanes |
You need ultraviolet radiation and a very high temperature of 300° C |
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What is another name for the halogenation of alkanes |
Free radical substitution |
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What is the limitation of free radical substitution |
A pure product cannot be formed straight away because lots of products can be formed (from further substitution and from the formation of structural isomers) |
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Why are alkenes more reactive |
Because they have a pi bond with a region of high electron density. Electrophiles can attacked this region of high electron density and cause alkene to react by breaking the pi Bond |
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What are stereoisomers |
They are molecules with the same structural formula but a different arrangement of atoms in space |
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What are the two conditions required for E-Z stereoisomers |
There has to be a double carbon Bond and two different groups attached to each carbon atom. |
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What is cis-trans isomerism |
A special case of E-Z isomerism in which one of the groups attached to each carbon is the same. |
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conditions are needed for the addition of hydrogen to an alkene |
A mixture of hydrogen gas and in gaseous alkene is passed over nickel catalyst 150° |
This is hydrogenation |
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what are the conditions for the addition of a halogen to an alkene |
Addition of halogen happens at room temperature when the alkene is shaken with a halogen. For example turning bromine water colourless |
This is known as halogenation |
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What are the conditions needed for the addition of a hydrogen halide |
halides are at room temperature and I'll bubbled into liquid alkenes |
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What are the conditions needed for the hydration of an alkene |
A high temperature and pressure in the presence of a phosphoric acid catalyst is needed |
This is the addition of steam |
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Between a primary and secondary carbocation, which one is more stable |
The secondary carbocation is more stable meaning the cob occasion where the positive carbon is bonded to 2 other carbon atoms |
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