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63 Cards in this Set
- Front
- Back
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What is an alkene? |
Compounds that contain at least one C=C bond |
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What is an example of a region of high electronegativity? |
Two shared pairs of electrons between 2 carbon atoms |
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What is the general formula of an alkene? |
CnH2n |
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When does the general formula of an alkene apply? |
When the compound only contains 1 C=C and is not cyclic |
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What type of isomerism can an alkene with 4 or more carbons exhibit? |
Position isomerism |
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What can you see if you compare the strength of the ō and π bonds in ethene? |
Ethene is a far more reactive molecule than ethane |
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What is the general equation of addition reactions of alkenes? |
H H \ / H \ / | | C = C + A-B ---> H - C - C - H / \ | | / \ A B H H |
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What is an electrophile? |
An electron deficient species |
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What mechanism do alkenes undergo when attacked by electrophiles? |
Electrophilic addition |
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What occurs in the first stage of electrophilic addition? |
Positive charge on electrophile attracted to electron density in double bond |
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What occurs as the electrophile approaches the double bond? |
Electrons in A-B bond are repelled towards B |
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What is the third stage of electrophilic addition? |
Pi bond breaks, A bonds to carbon to form a carbocation |
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What is a carbocation? |
Ion with positively charged carbon atom |
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What is the fourth stage of electrophilic addition? |
Two electrons in A-B bond move to B forming B- ion |
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What happens in the next stage of electrophilic addition? |
B- ion acts as nucleophile and attacks carbocation |
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What are the lone pair of electrons on the B- ion attracted towards? |
Positively charged carbon in carbocation, causing B to bond. |
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What is reaction 1 of electrophilic addition? |
Br2(l) with ethene |
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What equation represents reaction 1 of electrophilic addition? |
BR2 + C2H4 ----> CH2BrCH2Br |
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Why do the Br atoms in BR2 have a delta positive and negative charges? |
High electron density in C=C induces temporary dipole in BR2 causing one Br atom to be &+ and other to be &- |
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How can the presence of a carbon-carbon double bond (saturation) be detected? |
Using Bromine Water |
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What is process of testing for saturation (C=C)? |
Few drops of bromine water are added to the test liquid and shaken |
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What occurs if C=C are present? |
Bromine adds across it and bromine turns from orange to colourless |
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What is reaction 2 of electrophilic addition? |
Concentrated H2SO4 + ethane |
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What equation represents reaction 2? |
H2SO4 + C2H4 --> CH3CH2OSO2OH |
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What is the product of reaction 2? |
Ethyl hydrogensulfate - readily hydrolysed when warmed with water - intermediate |
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What is the purpose of sulfuric acid (H2SO4) in hydrolysis of ethyl hydrogensulfate? |
Catalyst |
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What is the simple equation of hydrolysis of hydrogensulfate? |
CH2CH2 + H2O --> CH3CH2OH |
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What is reaction 3 of electrophilic addition? |
HBr(aq) |
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What equation represents Reaction 3? |
HBr + C2H4 --> CH3CH2Br |
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How many products are formed in addition to an unsymmetrical alkene? |
1 - it makes no difference which C atom accepts the BR or H |
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What is a primary carbocation? |
When a carbon atom with a positive charge has only one carbon atom bonded to it |
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What is a secondary carbocation? |
When a carbon atom with a positive charge has two carbon atoms bonded to it |
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What is a tertiary carbocation? |
When a carbon with a positive charge has 3 carbon atoms bonded to it |
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What is the trend in stability in carbocations? |
As the carbocations increase, the stability increases (primary->secondary->tertiary) |
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Why as the number of alkyl groups bonded to C+ increases does the stability increase? |
Alkyl groups are electron releasing relative to hydrogen and help to stabilise the positive charge on the carbocation |
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Why is 2-bromopentane a major product? |
It is formed via a secondary carbocation and a secondary carbocation is more stable than a primary carbocation. |
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When is a polymer formed? |
When thousands of molecules called monomers join to a form a long chain molecule |
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What is addition? |
Breaking a double bond to form single bonds, 1 product formed |
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What are the two methods of making polymers? |
Addition Condensation |
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What occurs during addition polymerisation? |
Unsaturated molecules (alkenes) add together, forming a polymer |
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What are addition polymers named after? |
The monomers uses to make them |
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What is the prefix to describe a polymer? |
Poly- |
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What does n represent? |
A large number |
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How do you draw addition polymerisation? |
Alkene forms alkane ( double bond forms single bond, lines extending out from carbons |
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Addition polymerisation |
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Why do addition polymers tend to be unreactive? |
Saturated and usually non-polar - have to break strong C-C bonds |
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What sort of intermolecular forces occur in addition polymers? |
Weak intermolecular forces between polymer chains e.g. Van Der Waals, permanent d-d |
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How will increasing branching in the polymer structure effect the strength of the IMF between polymer chains? |
Increased branching means polymer chains have less points of contact as they can't pack closely together - weak VdW |
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What type of IMF forces occur in polychloroethene? |
Permanent dipole-dipole and Van Der Waals as there's a polar C-Cl bond --> hard and rigid |
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What is the effect of adding a plasticiser to vPVc? |
Lets chains slide so the polymer is flexible |
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What does an alcohol contain? |
The functional group -OH bonded to a carbon chain |
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What is the prefix and suffix of alcohols? |
Suffix -ol Prefix -hydroxy |
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How can alcohols be classified? |
Primary, secondary or tertiary - depends on number of carbon atoms directly attached to carbon atom carrying OH group |
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What is a primary alcohol? |
No/1 R group attached to same carbon chain as OH group |
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What is a secondary alcohol? |
2 R groups attached to same carbon chain as OH group |
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What is a tertiary alcohol? |
3 R groups attached to same carbon chain as OH group |
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What carbon chain does not need numbers in front of the methyl? |
Propane |
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What type of reaction do alcohols undergo when heated with concentrated sulfuric acid and aluminium oxide? |
Elimination |
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What is an elimination of water also referred to? |
Dehydration |
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What is dehydration? |
When water is lost as a component |
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What is the difference between dehydration and condensation? |
H2O in dehydration comes from 1 molecules, whereas H2O in condensation comes from 2 |
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What is sulfuric acid in dehydration? |
Catalyst at 450k |
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How many alkenes can be formed in an unsymmetrical alcohol? |
2 (position isomers) |
