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Chemistry > F322: Alkenes And Alcohols > Flashcards

F322: Alkenes And Alcohols Flashcards

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0
Q

Pi bond

A

Formed by the sideways overlap of adjacent p-orbitals above and below the plane of the molecule (sigma bond)

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1
Q

Alkenes

A

Unsaturated hydrocarbons; CnH2n; contain at least one C=C. Trigonal planar shape around each carbon in the C=C.

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2
Q

Electrophilew

A

Electron pair acceptor

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3
Q

Addition

A

When two molecules join together to make one (100% atom economy)

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4
Q

Hydrogenation (general formula + conditions)

A

Alkene + hydrogen -> alkane

Nickel catalyst, 150 degrees

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5
Q

Halogenation (general formula + conditions)

A

Alkene + halogen -> dihalogenoalkane

Room temp in the dark

(Can be used as test for alkenes, add bromine water, orange -> colourless)

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6
Q

Addition of hydrogen halides (general formula + conditions)

A

Alkene + hydrogen halide -> halogenoalkane

Room temp in the dark

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7
Q

Hydration (addition at steam) (general formula + conditions)

A

Alkene + steam -> alcohol

200 degrees, 200 atm, phosphoric acid catalyst

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8
Q

Addition polymerisation (general formula + conditions)

A

Alkene -> poly(alkene)

TiCl3 catalyst, 60 degrees

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9
Q

Industrial importance of alkenes

A

1) manufacture of margarine by catalytic hydrogenation of unsaturated vegetable oils using hydrogen and nickel catalyst.
2) formation of polymers eg. For plastics
3) manufacture of ethanol by hydration of ethene

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10
Q

Disposal of polymers

A

1) sort and recycle
2) combust for energy production
3) feedstock for cracking in the production of plastics and other chemicals

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11
Q

Role of chemists

A

To minimise the environmental damage from:

1) the removal of toxic waste products (eg. HCl (g) from combustion of halogenated plastics)
2) the development of biodegradable and compostable polymers

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12
Q

Alcohols

A

CnH2n+1OH; functional group ROH. Short chained alcohols are soluble in water. Higher melting points than corresponding alkanes due to their ability to form hydrogen bonds.

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13
Q

Classification of alcohols

A

Primary: OH attached to carbon which is attached to 1 other C
Secondary: OH attached to carbon that has 2 C attached to it
Tertiary: OH attached to a carbon that has 3 other C attached to it

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14
Q

Industrial production of ethanol (fermentation of sugars)

A

fermentation of sugars (glucose)
C6H12O6 -> 2C2H5OH + 2CO2

Conditions: yeast, 37 degrees, absence of air
Advantages: sugar cane is renewable, low temperature required
Disadvantages: slow batch process, mixture of products (low atom economy)

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15
Q

Industrial production of ethanol (hydration of ethene)

A

Hydration of ethene:
C2H4 + H2O (g) -> CH3CH2OH

Conditions: H3PO4 catalyst, 200 degrees, 200atm
Advantages: pure ethanol (100% atom economy), fast process
Disadvantages: non-renewable ethene from crude oil, hight temp

16
Q

Biofuel

A

Fuel made from animal or plant waste material

17
Q

Use of alcohols

A

1) ethanol in alcoholic drinks

2) methanol as a petrol additive to improve combustion as a feedstock

18
Q

Combustion of alcohols

A

Alcohol + oxygen -> CO2 + H2O

19
Q

Oxidation of alcohols -> oxidising agent/conditions/observations

A

[O] -> acidified dichromate ions (H+/Cr2O7 2-)
Conditions: K2Cr2O7 and H2SO4
Observation: Orange to green

20
Q

Oxidation of primary alcohols (partial)

A

Partial oxidation: => aldehyde
Conditions: Distill product immediately, acidified potassium dichromate.
CH3CH2OH + [O] -> CH3CHO + H2O (Ethanol -> Ethanal)

21
Q

Oxidation of primary alcohols (full)

A

Full oxidation: => carboxylic acid
Conditions: Reflux, acidified potassium dichromate
CH3CH2OH + [O] -> CH3COOH + H2O (Ethanol-> Ethanoic acid)

22
Q

Oxidation do secondary alcohols

A

=> Ketones
Conditions: acidified potassium dichromate
CH3CH(OH)CH3 + [O] -> CH3CH(O)CH3 (Propan-2-ol -> Propanone)

23
Q

Oxidation of tertiary alcohols

A

Tertiary alcohols are NOT oxidised (thus reaction mixture stays orange)

24
Q

Esterification of alcohols

A

Aka: Condensation (loss of water)
Alcohol + carboxylic acid -> ester + H2O
Eg. Methanol + propanoic acid -> methylpropanoate + H2O

Conditions: conc H2SO4 catalyst, REFLUX

25
Q

Dehydration of alcohols

A

Aka: elimination (dehydration- loss of water)
Conditions: conc H2SO4 catalyst, heat
Alcohol -> alkene + H2O

26
Q

Reflux

A

Continuous evaporation and condensation to prevent the loss of volatile components (those with low boiling points)

27
Q

Elimination

A

The loss/removal of a small molecule from a larger molecule (eg. Dehydration-> water)

Chemistry (84 decks)

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