Unit 2 Organic Chemistry

  • Created by: Naana
  • Created on: 27-04-15 20:39
What is a haloalkane?
An alkane with at least one halogen atom in place of a hydrogen atom
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What is a nucleophile?
A species with a lone pair of electrons to donate.
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What does a nucleophile do?
It attacks positively charged carbon atoms and forms bonds with electron deficient carbon atoms by donating it electrons to the carbon atom
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Give 3 examples of common nucleophiles
:CN, :NH3, :OH
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Why are carbon- halogen bonds polar?
Because halogens are more electronegative than carbon
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What is the trend in bond polarity in group 7?
Bond polarity increases up group 7 as electronegativity increases up gp 7. C-F bond is the most polar as fluorine is the most electronegative element
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What is the trend in bond enthalpies in group 7?
As we go down group 7 the bonds get weaker and longer as the halogen atom get bigger. As a result, the compounds with the weakest bonds are the most reactive
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What is the solubility of haloalkanes in water?
They are not soluble in water as they are not very polar. The longer the hydrocarbon chain gets, the less polar they get so they become even more insoluble
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What are the trends in boiling point in group 7?
Boiling point increases down group 7 because as the molecules get larger, there are more electrons and so the v.d.w’s forces get stronger. Also the boiling point increases as the hydrocarbon chain length increases
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Why do haloalkanes have higher boiling points than alkanes of similar chain lengths?
Because they have higher Mr and they are more polar
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What is nucleophilic substitution?
An organic reaction in which a molecule with a partially positive carbon atom is attacked by a nucleophile and the nucleophile replaces a functional group in that molecule
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What is an elimination reaction?
A reaction where an atom or a group of atoms are removed from the larger molecule and are not replaced by anything else
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What happens when haloalkanes are eliminated?
The halide (a negative ion of a halogen) is eliminated and a double bond is left in its place so that an alkene is formed
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What are chlorofluorocarbons (CFC’s)?
They are haloalkane molecules where all the hydrogen atoms have been replaced by chlorine and fluorine atoms. Short chain CFCs (gases) used as aerosol propellants. Long chain (liquids) used as dry cleaning solvents
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Why are CFCs harmful to the environment?
When CFC gases end up in the atmosphere they decompose to give chlorine atoms when the energy from the UV radiation causes the C-Cl bonds in CFCs to break. The chlorine atom then forms free radicals( Cl. ) when the UV radiation breaks the Cl-Cl bonds
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What is a free radical?
A species with an unpaired electron making it highly reactive
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What happens when a bond breaks homolytically?
One electron goes to each atom
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What happens in the initiation stage of a chain reaction?
Free radicals are produced when the energy from UV radiation causes the Cl-Cl bond to break homolytically forming two chlorine atoms with a unpaired electron (free radicals)
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What happens in the propagation stage of the chain reaction?
Free radicals are used up in chain reactions and then regenerated (new free radical created). This is the chain part of the chain reaction as this step only stops when all the reactants have been used up
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What happens in the termination stage of the chain reaction?
Free radicals react to form a stable compound with no unpaired electrons
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What is a homogeneous catalyst?
A catalyst which is in the same phase as the reactants
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What are the physical properties of alkenes?
Alkenes are insoluble in water as they are non polar molecules. Melting and boiling points increase as the chain length increases
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Why are alkenes more reactive than alkanes?
The C=C in alkenes form an electron rich area as there is high electron density. As a result they are easily attacked by electrophiles (electron liking reagents)
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What are electrophiles?
A species which can accept a pair of electrons
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What are electrophilic addition reactions?
A reaction where the double bond in an alkene opens up and atoms are added to the carbon atoms
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What is the most stable carbocation?
The tertiary carbocation as it has the most alkyl groups. It has 3 alkyl groups releasing electrons towards the positive carbon.
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What carbocation is more likely to form?
More stable carbocations are more likely to form than less stable ones
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What are position isomers?
They are isomers with the double bond in different positions
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What are geometrical isomers?
It is when compounds have the same structural formula but the bonds are arranged differently in space. It occurs only around the C=C bond and is a type of stereoisomerism
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What are some uses of polyethene?
Plastic bags, washing up bowls
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What is addition polymerisation?
When the double bonds in alkenes open up and join together to form a long chain molecules (polymer) made of repeating units of monomers
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How are alcohols classified?
Alcohols are classifies as primary, secondary and tertiary depending on how many other R groups are bonded to the carbon atom that has the -OH group attached. \Primary= 1 alkyl group, Secondary= 2 alkyl groups, tertiary= 3 alkyl groups attached to t
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What are the physical properties of alcohols?
Higher melting and boiling point than alkanes because hydrogen bonding occurs between the molecules due to the OH group. Short chain alcohols are soluble in water as hydrogen bonds can form between the OH groups and water molecules
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How is ethanol produced industrially?
By reacting ethene with steam and using a catalyst of phosphoric acid
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Other cards in this set

Card 2


What is a nucleophile?


A species with a lone pair of electrons to donate.

Card 3


What does a nucleophile do?


Preview of the front of card 3

Card 4


Give 3 examples of common nucleophiles


Preview of the front of card 4

Card 5


Why are carbon- halogen bonds polar?


Preview of the front of card 5
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