Organic chemistry Flashcards

1
Q

What are the two ways cracking can be done

A

-Passing alkane vapour over a catalyst
-Mixing alkane vapour with steam
Before heating to a very high temperature

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2
Q

Where would cracking place in industry?

A

Cracking unit in fractional distillation column

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3
Q

How would cracking happen in a lab

A

Porcelain chips would act as catalyst. Vapour would be passed over hot powdered aluminium oxide catalyst
Long chain molecules split apart on surface of specks of catalyst

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4
Q

How can you crack carbons with vapour?

A

Mix with steam, and heat to high temp

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5
Q

How can product gas prove it has alkenes in it?

A

Bubble through bromine water because alkenes more reactive than alkanes and so they react with bromine water turning this liquid from orange to colourless.

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6
Q

What is an alkene

A

A hydrocarbon with a double c=c bond (covalent)

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7
Q

What is the formula for alkenes

A

CnH2n

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8
Q

Why do alkenes not have methane as part of their series

A

Because methane is one carbon and alkenes have to have a double bond so need more than one carbon

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9
Q

Why are alkene molecules unsaturated

A

Because they contain fewer hydrogen atoms than the alkane with the same number of carbon atoms

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10
Q

Name the first 4 alkenes

A

Ethene
Propene
Butene
Pentene

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11
Q

Explain but-1-ene

A

Means the double bond is in the first c-c bond of the butene molecule

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12
Q

How are alkenes more reactive than alkanes?

A

The c=c bond can open make a single bond allowing 2 carbon atoms to bond with other atoms

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13
Q

Which hydrocarbon fractions are in the greatest demand?

A

Fractions containing smaller hydrocarbons- used for fuels. Global demand for small hydrocarbons high and excess of large. Solution is cracking.
Larger carbons for Road surfacing e.g. Bitumen

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14
Q

How do most alkenes react

A

Via addition reactions.

C=c bond will open up and leave a single bond and a new atom to each carbon

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15
Q

What 4 reactions do alkenes undergo?

A

Hydrogen
Oxygen
Halogens
Water (steam)

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16
Q

Explain alkene reaction with hydrogen

A

Saturated alkANE made.

Reaction called hydrogenation and occurs at 150°c with nickel catalyst

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17
Q

Explain alkene reaction with oxygen

A

Combustion reactions.
Don’t generally combust alkenes however because:
Burn with smokey flame due to incomplete combustion
Useful as starting materials for making polymers, alcohols, medicines

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18
Q

Explain alkene reaction with halogens

A

Addition reaction.

Hydrogen atoms added across c=c bond to make any c-c bond (saturated)

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19
Q

Explain alkene reaction with water (steam) and explain what conditions are required

A

Addition reaction
OH, H added across c=c bond: hydration reaction.
High temps, high pressure and concentrated phosphoric catalyst needed.

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20
Q

What is the alcohol functional group and how does the unit differ

A
  • OH-

- ch2h-

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21
Q

What are the 4 reaction with alcohols

A

Water
Oxygen
Oxygen
Sodium metal

22
Q

Explain reaction of alcohol with water

A

Alcohols posses covalent bonds that do not break easily, so dont react with water other than dissolve in it. Eg ethanol in vodka

23
Q

Explain reaction of alcohol with oxygen (combustion)

A

Alcohols are flammable and burn in air why often used as fuels. Eg spirit burners. Burn cleanly and not smelly.
Produce co2 and h20

24
Q

Explain reaction of alcohol with oxygen (mild oxidation)

A

A mild oxidising agent will gently add oxygen or remove hydrogen from a mol without breaking it apart.
Oxidising agents: O2 in air, microbes.
Produce CARBOXYLIC ACID

25
Q

What is the most common example of alcohol with oxygen?

A

Wine containing ethanol oxidised in air to make vinegar (ethanol acid)

26
Q

Explain the reaction of sodium metal with alcohol

A

Produce a hydrogen gas and basic solution.

27
Q

Give 2 other uses of alcohols

A

Good solvents-n used to dissolve perfume molecules and medicines that are not soluble in water.
Aq solutions of ethanol are produced when sugar solutions are fermented using yeast- FERMENTATION.
Yeast
Sugar———> ethanol + co2

Conditions: yeast, no oxygen, room temp

28
Q

What is crude oil

A

A finite resource

Mixture of large compounds (hydrocarbons)

29
Q

How many bonds does an alkane have

A

1

30
Q

What is an homologous series?

A

A group of compounds that react in similar ways

31
Q

How do alkanes differ from one and other

A

CnH2n+n

32
Q

What are the first 4 alkanes

A

Methane
Ethane
Propane
Butane

33
Q

What is the smallest and biggest hydrocarbon

A

Methane and bitumen residue

34
Q

Describe the process of fractional distillation

A

1.Crude oil is heated and most evaporated to vapour
2.Gases enter fractioning column and liquid drains off
There’s a temp gradient in the column- hot at bottom cooler as you go up
3. Longer HCs condense back into liquid and drain out of column near bottom because higher boiling point
4. Shorter HCs condense and drain out much later on at top of column because lower boiling point.

35
Q

What is the final result of fractional distillation

A

Crude oil mixture separated into different fractions. Each fraction contains a mixture of HCs- similar number of carbon atoms and similar boiling points

36
Q

What is fractional distillation?

A

HCs separated into fractions each containing molecules with similar number of carbon atoms.
These fractions can be processed to produce fuels and feedstock for chemical, industry eg. Make medicines or plastics.

37
Q

What do the properties of hydrocarbons depend on

A

Their size

38
Q

What factors influences how hydrocarbons are used as fuels?

A

Boiling point
Flammability
Viscosity

39
Q

Describe boiling point

A

Larger molecule higher
Because greater intermolecular forces require more heat/ energy to gain enough speed or energy to leave the surface of the liquid and become a gas

40
Q

Describe flammability

A

Smaller mol burn easier- used for fuels- weaker

Larger mol tend not to burn

41
Q

Describe viscosity

A

Larger mol more tangled posses greater intermolecular forces less able to move past each other
Like spaghetti

42
Q

What happens in the combustion of hydrocarbons

A

H oxidised to form H2O
C oxidised to form CO2
Energy given out in form of heat and light

Hydrogen+oxygen—> H2O+CO2

43
Q

What is cracking

A

Thermal decomposition (large alkanes heated to vapour and broken up)

44
Q

What is made in cracking

A

Mixture of alkenes and alkanes

45
Q

What is the functional group of carboxylic acids

A

COOH

46
Q

What do carboxylic acids react with

A

Water
Carbonates
Alcohols

47
Q

How does a carb acid react with water

A

They dissolve easily in water

The partially ionic OH bond will partially react with water by partially dissociating to form carboxylate ion (COO)

48
Q

Describe the dissociation process

A

Called IONISATION
results in production of H+ ions making solution acidic
As dissociation only partial only some H+ ions are made at one time and acid solution is weak- weak acids

49
Q

Describe reaction of carb acid with carbonate

A

Form salt co2 and water

50
Q

Describe carb acid with alcohols

A

Can be reacted together if small amount of concentrated sulfuric acid present to act as catalyst
Mol of water is removed from carb acid and alcohol and remaining fragments combine together
Conc of sulfuric acid able to catalyse reaction because it absorbs the water strongly encouraging reaction to proceed
ESTER IS MADE -COO