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Chemistry > 2 - Organics > Flashcards

2 - Organics Flashcards

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1
Q

Why is Cracking important?

A

Converts low-demand fractions into higher demand fractions

Makes useful hydrocarbons not normally found in crude oil

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2
Q

What are the conditions for thermal cracking?

A

High temp + pressure

Makes high percentage of small alkenes

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3
Q

What are the conditions for catalytic cracking?

A

High temp + slight pressure + zeolite catalyst
More efficient
Zeoloite catalyst favours the formation of branched and cycloalkanes

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4
Q

What are the pollution problems caused by burning hydrocarbons?

A

Global warming
Water vapour is a greenhouse gas
Carbon monoxide and carbon from incomplete combustion
Sulphur dioxide - acid rain
Nitrogen oxides - acid rain and acidic water and petrochemical smog

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5
Q

Ways of reducing pollution from hydrocarbon combustion?

A

Flue gas desulphurisation

Catalytic converters - converts oxides of nitrogen and CO

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6
Q

Describe covalent double bonds.

A

Sigma - side-on overlap, atomic orbitals between the nuclei
Pi - end on overlap, atomic orbitals above and below
Overlap in two places causes restricted rotation

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7
Q

What is E/Z isomerism?

A

Both hydrogen atoms on the same side of the double bond - Z

Both hydrogen atoms on the opposite side of the double bond - E

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8
Q

What is the pi bond in an alkene like?

A

Area of high electron density and can thus attract electrophiles

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9
Q

What is Heterolytic fission?

A

The breaking of a covalent bond which results in both electrons going to the same atom

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10
Q

Describe electrophilic addition of alkene

A

A hydrogen halide or halogen will be attracted by the double bond causing a bond to form breaking the double bond and leaving a radical nucleophile which bonds to the second un-bonded carbon.

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11
Q

Describe hydrogenation

A

Adding hydrogen to saturate the double bond of an alkene using 200 degrees and a nickel catalyst. (Makes alkane)

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12
Q

How is the presence of a double bond detected?

A

Bromine water that causes a brown to colourless change

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13
Q

What is Markownikoff’s rule?

A

“The more electronegative part of the electrophile will usually attach itself to the more highly substantiated carbon atom”

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14
Q

What are the major and minor products of electrophilic addition called?

A

Markownikoff product and the anti-Markownikoff product

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15
Q

What does electrophilic addition of an alkene produce?

A

Halogeno-alkanes

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16
Q

Describe hydration of an alkene

A

Addition of steam, at 300 degrees, 60 atmospheres and using a phosphoric acid catalyst. It produces an alcohol.

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17
Q

Advantages of fermentation

A

Low-tech process
Not use much energy (35-55 degrees)
Uses sugar cane which is renewable

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18
Q

Disadvantages of fermentation

A

Batch process
Slow process
Unethical

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19
Q

Other than fermentation how can ethanol be produced?

A

hydration of ethene - adding steam at 300 degrees, 60 atmospheres and a Phosphoric acid catalyst

20
Q

Advantages of hydration

A

Fast process
Continuous process
Produces pure ethanol

21
Q

Disadvantages of hydration

A

High tech - expensive
Uses a lot of energy
ethene comes from crude oil which is non-renewable

22
Q

What is produced when burning ethanol?

A

CO2 and H20

23
Q

Describe the elimination of alcohols

A

Elimination reaction of alcohol. Concentrated phosphoric acid (H3PO4) used to remove water and make an alkene.

24
Q

What does the elimination of alcohols produce?

A

Alkenes (removal of H2O)

25
Q

What forms when a primary alcohol is mildly oxidised?

A

aldehyde (anal) (COH)

26
Q

What forms when a secondary alcohol is mildly oxidised?

A

Ketone (anone) (COC)

27
Q

Why can’t tertiary alcohols be oxidised?

A

No available H atoms

28
Q

What is formed when an aldehyde is further oxidised?

A

Carboxylic acid as an extra oxygen is added (COOH)

29
Q

What can be used as an oxidising agent?

A

Concentrated Potassium dichromate

30
Q

What can be used to test for Aldehydes?

A

Tollens reagent - forms ‘Silver Mirror’

31
Q

What is a substitution reaction?

A

A reaction in which one atom or group of atoms on the organic molecule is directly replaced by another.

32
Q

How are free radicals formed?

A

homolytic fission - breaking a covalent bond in which one electron goes to each atom

33
Q

What are the three steps and conditions for free radical substitution?

A

Initiation, Propagation, Termination and UV light required

34
Q

What can be done to make sure the major product is achieved in free radical substitution?

A

Excess of alkane

35
Q

What does free radical substitution make?

A

Halogenoalkanes

36
Q

What do halogenoalkanes react with?

A

Nucleophiles as the C-X bond is slightly positive

37
Q

Describe the reaction of halogenoalkanes and hydroxide ions

A

Nucleophilic Subsitiution .The hydroxide ion (acting as a nucleophile) attacks the carbon from behind forcing the X atom to leave as an ion. It does this under boiling with reflux with aqueous NaOH or KOH. It makes an alcohol.

38
Q

Describe the reaction of an alkene and H2SO4

A

Electrophilic of cold concentrated sulphuric acid + then warm and add water. An alcohol is formed. This is hydrolysis.

39
Q

Describe the reaction of halogenoalkanes and cyanide ions (CN-)

A

Nucleophilic substitution. Boiled under reflux with KCN in aqueous ethanol. The Carbon in the cyanide attacks the carbon. CN- ion attacks carbon and halogen ion is formed. It is a very useful reaction for ascending the homologous series as it increases the number of carbons on the chain.

40
Q

Describe the reaction of halogenoalkanes and ammonia (NH3)

A

Nucleophilic substitution. Heated with ethanol. Primary amine formed. Halogen ion formed.

41
Q

Describe the elimination of halogenoalkanes

A

Produces an alkene. Ethanolic solution of KOH used. OH ion attacks hydrogen, forms water. curly arrows go from ion to H to C-C bond to X. Loss of X. Hydroxide ion acts as nucleophile.

42
Q

Describe the rates of reaction for the Halogenoalkanes

A

Increases down group as halogen atom becomes larger, the C-X bond becomes longer, weaker and easier to break thus reacting more quickly.

43
Q

Describe dehydration.

A

Elimination reaction of alcohol. Concentrated phosphoric acid (H3PO4) used to remove water and make an alkene.

44
Q

How to make chloroalkane from alcohol? (Chlorination)

A

Add PCL, HCL produced, misty white fumes, only works with primary and secondary alcohols.
For tertiary shake with aqueous HCL, water produced

45
Q

How to make bromoalkane from alcohol? (Bromoalkane)

A

Warm gently with HBr, makes H20
To make HBr, add KBr to conc H2SO4
KBr + H2SO4 –> KHSO4 + HBr

46
Q

How to make iodoalkane from alcohol? (iodonation)

A

Reflux with PI3, makes H3PO3
To make PL3, add Red phosphorus to 3 iodines
2P + 3I2 –> 2PI3

Chemistry (8 decks)

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