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C7 (organic chemistry) Flashcards

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1
Q

how is crude oil formed?

A
  • found in rocks - it’s a finite resource (will run out some day).
  • 300-400 million years ago, organisms (such as plankton) died, sank to seabed. sediment fell on top of them. sediment and the water on top of them created high pressures and temperature, preventing them decomposing. formed crude oil, then extracted from the rocks.
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2
Q

what is a hydrocarbon?

A

a compound of carbon and hydrogen only. (e.g. crude oil is made up of a mix of different hydrocarbons. the temperature and pressure the solution is exposed to determines the types of hydrocarbons in the mixture).

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3
Q

what are the four types of alkanes and their formulas?

A
  • methane (CH4)
  • ethane (C2H6)
  • propane (C3H8)
  • butane (C4H10)
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4
Q

what is the formula for alkanes?

A

Cn (H2 x n +2)

However many carbon atoms there are, double it and add two to find the number of hydrogen atoms.

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5
Q

what is an alkane?

A

scientists say that alkanes are saturated molecules. this is because the carbon atoms are fully covalently bonded to the hydrogen atoms.

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6
Q

why is the process of fractional distillation important?

A
  • crude oil is made up of many hydrocarbons with different boiling points.
  • we must separate them in order for the hydrocarbons in the oil to be useful, and we do this through fractional distillation.
  • in fractional distillation, crude oil is separated into fractions - these contain hydrocarbons with a similar number of carbon atoms.
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7
Q

describe the process of fractional distillation:

A
  • takes place in large columns in oil refineries.
  • the crude oil is heated to a very high temperature, causing it to boil.
  • all the hydrocarbons evaporate and turn into a gas, which is then fed into the bottom of a fractional distillation column (above).
  • the column is hotter at the bottom and cooler at the top.
  • the hydrocarbon vapours now rise up the column.
  • the different hydrocarbons condense (turn into liquid) at different points up the fractionating column, when they reach their boiling point. the liquid fractions are then removed.
  • very long chain hydrocarbons have very high boiling points, and so are all removed at the bottom of the fractionating column.
  • very short chain hydrocarbons have very low boiling points, and do do not condense. these are removed at the top of the fractionating column as gases.
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8
Q

describe fractions and their uses:

A

fractions contain hydrocarbons with a similar number of carbon atoms.

  • petrol and diesel fuels cars.
  • kerosene is used as jet fuel.
  • heavy fuel oil is used to power ships.
  • liquified petroleum gas is used in camping stoves.
  • some fractions are used as feedstock (chemical used to make other chemicals) for the petrochemical industry.
  • solvents
  • lubricants
  • detergents
  • polymers
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9
Q

how does hydrocarbon chain length affect viscosity?

A

viscosity = the thickness of a fluid.
- fluids with a high viscosity flow slowly, e.g. honey.

  • as the hydrocarbon molecule size increases, the molecules get more viscous. very long chain hydrocarbons flow very slowly.
  • this is because it takes more energy for longer chain lengths to flow over itself.
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10
Q

how does hydrocarbon chain length affect flammability?

A

flammability = how easy hydrocarbons combust.

  • short chain hydrocarbons are very flammable - methane is the gas used in bunsen burners.
  • as the size of hydrocarbon molecules increases, the molecules become less flammable.
  • this is because it’s less able to evaporate and convert into gas form.
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11
Q

how does hydrocarbon chain length affect the boiling point?

A

boiling point = temperature at which a liquid turns into a gas.

  • short chain hydrocarbons have low boiling points.
  • as chain length increases, the number of intermolecular forces increases - more energy is needed to separate longer molecules, meaning they have higher boiling and melting points.
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12
Q

what are the two main features of alkanes?

A
  • general formula of Cn (H2n+2)
  • only have single covalent bonds between carbon atoms.
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13
Q

what is the disadvantage of using long-chain hydrocarbons as fuels?

A
  • not very flammable, don’t make good fuels.
  • short chain hydrocarbons are flammable, and are under high demand - finite resource.
  • must convert long-chain hydrocarbons into shorter-chain hydrocarbons.
  • this process is called cracking.
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14
Q

what is cracking?

A
  • thermal decomposition reaction.
    long chain hydrocarbon broken down to produce smaller, more useful molecules.
  • this makes one shorter chain alkane (used for fuels in cars).
  • also makes an alkene molecule.
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15
Q

what are the required conditions for cracking?

A
  • catalytic cracking: high temperature and catalyst (speeds up reaction).
  • heat long chain hydrocarbons, vaporise them.
  • use hot powdered aluminium oxide as the catalyst, and pass the vaporised hydrocarbon over it.
  • as the long hydrocarbons come into contact with the catalyst, they split apart.
  • steam cracking: high temperature and steam.
  • heat long chain hydrocarbons, vaporise them.
  • mix the vaporised hydrocarbons with steam, and heat them to a very high temperature.
  • this causes the long hydrocarbons to split apart.
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16
Q

describe alkenes:

A
  • (e.g. ethene) has double covalent bond between two carbon atoms. this makes them unsaturated - alkanes only have single bonds, making them saturated.
  • very useful. used by adding them together to make polymers. the double bond can break to form two or more bonds to connect the adjacent atoms.
  • used as starting material for other useful chemicals.
  • more reactive than alkanes - has a double bond which can easily split open.
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17
Q

what are the four alkenes and their formulas?

A
  • methene (CH2)
  • ethene (C2H4)
  • propene (C3H6)
  • butene (C4H8)
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18
Q

how do you test for alkenes?

A
  • uses bromine water, which is orange.
  • if you shake an alkene solution with bromine water, the bromine water will turn from orange to colourless.
  • the bromine molecules replace the double bond in the alkene molecule. there is now no bromine molecule to keep the orange colour of the solution - this won’t happen with alkanes, as there is no double bond to break.
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19
Q

why do you get one alkane and one alkene when you split long chain hydrocarbons?

A
  • take decane, which splits to make heptane and propene.
  • as decane is ten carbons long, it splits to make heptane (7 carbons) and propene (3 carbons).
  • if you did the same for hydrogens, there aren’t enough hydrogens left for both products to be saturated and have all single bonds.
  • therefore, one of the products has to have a double bond, making it an alkene, rather than an alkane.
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20
Q

what is a homologous series?

A

a group of similar compounds with similar properties.

  • alkanes and alkenes are both homologous series.
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21
Q

what is the alkene formula?

A

Cn H2n

the number of hydrogen atoms is double the number of carbon atoms.

22
Q

what is the functional group of alkenes?

A

the carbon-carbon double bond is the alkene’s functional group, as its responsible for the alkene’s typical reactions.

23
Q

what are addition reactions?

A

the double bond in the alkene opens up, so the two carbon atoms are able to bond to two atoms of another molecule, therefore ‘adding’ to the alkene. hence the name, addition reaction.

24
Q

what are the products of complete and incomplete combustion?

A

complete combustion:
alkane/alkene + oxygen = water + carbon dioxide

incomplete combustion:
alkane/alkene + oxygen (limited/insufficient) = carbon monoxide + carbon (soot)

25
Q

describe the addition reaction of alkenes with hydrogen (hydrogenation):

A
  • take propene (three carbon chain).
  • adding hydrogen to propene and supplying a catalyst will cause the double bond in the alkene to break apart, and the hydrogen atoms will then be able to bond to those carbon atoms.
  • the product is propane, and it doesn’t have a double bond anymore. it’s now saturated.
26
Q

describe the addition reaction of alkenes with water (hydration):

A
  • take ethene, and add water to it. react it with a catalyst and high temperatures.
  • the water will actually be in the form of water vapour/steam.
  • the double bond on the alkene opens up, and the water molecule will split into a hydrogen atom and an O-H group. these can then bond with the vacant carbon atoms.
  • the product is ethanol (an alcohol), as it as the O-H functional group
27
Q

how do you separate ethanol from unreacted ethene and water after hydration?

A
  • ethanol is used in many industrial processes, and is used to create alcoholic drinks.
  • as ethene has a relatively low boiling point, cool the molecule, so the ethanol and water will condense into liquid form, while the ethene will remain a gas.
  • to separate the water and ethanol, you must use fractional distillation.
  • heat the mixture, the ethanol will boil first (lower boiling point), and will evaporate up through the fractionating column and then condense into a separate beaker.
28
Q

describe the addition reaction of alkenes with halogens (halogenation):

A
  • use ethene as an example.
  • take ethene, add it to bromine, and give it a shake. this will react to form dibromoethane.
  • as this uses up all of the bromine, the orange colour disappears.
  • the main test we use to distinguish alkenes from alkanes.
29
Q

describe alcohols:

A
  • homologous series
  • look same as alkanes, but has O-H functional group, in the place of one of the hydrogens.
30
Q

what are the four types of alcohol and their formulas?

A
  • methanol (CH3OH)
  • ethanol (C2H5OH)
  • propanol (C3H7OH)
  • butanol (C4H9OH)
  • always put OH at the end
31
Q

what is the general formula for alcohols?

A

Cn (H2n+1) OH

32
Q

what are the properties of alcohols?

A
  • flammability. can undergo complete combustion in air (makes a blue flame). react with oxygen to form carbon dioxide and water.
  • solubility. can dissolve in water to form a solution. alcohols aren’t acidic or alkaline, so the solution will have a neutral pH.
  • oxidisation. taking an alcohol and adding oxygen can form a carboxylic acid, which has the functional group of ‘COOH’.
33
Q

what are the uses of alcohols?

A
  • fuels (bio-fuels) as they’re flammable (releases lots of energy)
  • solvents in industry. often used instead of water, as it can dissolve things that water can’t. e.g. hydrocarbons, lipid compounds (fats, oils).
  • food and drink (ethanol only)
  • sanitiser
  • anti-septic
34
Q

what are the four carboxylic acids and their formulas?

A
  • methanoic acid (HCOOH)
  • ethanoic acid (CH3COOH)
  • propanoic acid (C2H5COOH)
  • butanoic acid (C3H7COOH)
  • COOH is the functional group of carboxylic acids.
35
Q

describe carboxylic acids:

A
  • weak acids (only partially ionise). they don’t lose all their hydrogen atoms.
  • low concentration of H+ ions. pH of 4-6.
  • this shows propanoic acid ionising. the acid on the right hand side of the equation is negative, and forms a propanoate ion .
  • C2H5COOH = C2H5COO- + H+
  • equilibrium arrow. loses some hydrogen, not all.
36
Q

describe the reaction of a carboxylic acid with a metal carbonate:

A

carboxylic acid + metal carbonate = salt + water + carbon dioxide.

e.g. ethanoic acid + potassium carbonate = potassium ethanoate + water + carbon dioxide.

37
Q

describe esters:

A
  • their functional group is COO. can also be called ester group/ester link - links together carboxylic acid and alcohol.
  • pleasant smell - sweet/fruity. used in perfumes, food colourings.
  • volatile (evaporates quickly) - makes it good for perfumes, as you then buy more.
  • also used in nail polish removers, glue, and decaf drinks.
38
Q

how do you make esters?

A

carboxylic acid + alcohol (acid catalyst, typically sulfuric acid) = ester + water

ethanoic acid + ethanol = ethyl ethanoate + water

  • the water is a by-product, formed from the OH from the carboxylic acid and the H from the ethanol.
39
Q

what are addition polymers formed from?

A

polymers are formed from alkenes. for example, if you lined up three ethene molecules next to each other, their carbon-carbon double bonds could split open to connect to their adjacent molecules.
- this forms one long chain (a polymer)

40
Q

how would you show the reaction of an alkene becoming an addition polymer?

A

show the three alkene molecules on the left (these are our monomers). draw an arrow, detailing that a catalyst and high pressures are required to form the polymer, which will be drawn on the right.

  • these reactions however sometimes involve hundreds of monomers, which would take ages to draw.

instead, draw a single monomer on the left, and a single repeating unit of the polymer on the right. put both units in brackets.

  • draw monomer bonds up and down, instead of out at angles.
  • for the polymer, draw the empty bonds pointing out through the left and right, passing through the brackets.
  • put n’s outside of the brackets, showing how many monomers and repeating units there are.
41
Q

how do you name a polymer?

A

put the word ‘poly’ in front of the monomer’s name. put the monomer name in brackets.

  • e.g. ‘butene’ becomes ‘poly(butene)’
42
Q

what are condensation polymers and how are they formed?

A
  • made up of many individual monomers.
  • they’re usually made up of 2 different types of monomers.
    - dicarboxylic acid monomer
    (carboxylic acid)
    - diol monomer (alcohol)
  • process forms water molecules.
  • dicarboxylic acid must give up OH group. diol must give up hydrogen atom from its OH group. these three atoms combine to form a water molecule.
  • this leaves a carbon from the dicarboxylic acid to bond directly to an oxygen from the diol monomer, forming a bond which we call the ‘ester link’ - COO.
  • at this point, the molecule is just a dimer, as it’s only two molecules combined.
  • to show it as a polymer, remove an OH and an H atom from the ends, forming another water molecule. these carbon bonds can now stick through brackets and form a polymer.
43
Q

what is the reaction equation for polyester?

A

dicarboxylic acid + diol monomer = condensation polymer (polyester) + 2H2O

  • as this process often occurs with hundreds or thousands of monomers, place an n in front of each reactant and product:

e.g. n dicarboxylic acid monomer + n diol monomer = n condensation polymer (polyester) + 2n H2O

44
Q

what do molecules require to be able to combine in condensation polymers?

A
  1. each of the monomers has to have at least two functional groups.
    • e.g. dicarboxylic acid monomers have
      two COOH functional groups, diol
      monomers have two OH functional
      groups.
  2. must be at least two different functional groups overall.
    • e.g. has one carboxyl group and one
      alcohol group.
  3. a small molecule is given off in the process.
    • e.g. generally water.
45
Q

why are polyesters biodegradable?

A

they can break down naturally because bacteria and other micro-organisms can break down the ester links.
- this is the big difference to addition polymers, which are usually plastics, so aren’t biodegradable.

46
Q

what are polypeptides and how are they linked to proteins?

A
  • amino acids in one long chain are called polypeptides.
  • when the polypeptide folds up or combines with other polypeptides, we call it a protein.
  • as there are many types of amino acids, and they can combine in many different ways, this results in a wide range of proteins that can do a wide range of things.
  • it can catalyse chemical reactions (enzymes)
  • provide structure and strength to tissues in our bodies.
47
Q

what is the structure of an amino acid?

A
  • always contains a carboxyl group, and an amino group.
  • always joined together by a central carbon.
  • there is a group at the bottom called an ‘R’ group, which changes depending on which amino acid it is, making all amino acids different.
48
Q

how do amino acids join together to form a polymer?

A
  • the amino and carboxyl functional groups of the amino acid allows adjacent amino acids to join together through condensation reactions.
  • the OH from the carboxyl group and the H from the amino group react together to produce water.
  • the amino acids now join together, as the carbon on the carboxyl functional group and the nitrogen on the amino group can bond.
  • this bond can be called an ‘amide bond’, an ‘amide link’ or a ‘peptide bond’.
49
Q

describe DNA:

A
  • monomers are structures called nucleotides. they all contain a small molecule called a base. the rest of the nucleotide stays the same.
  • by combining these different nucleotides in different orders, our cells can make different codes, which we call genes.
  • to prevent these codes intact and prevent them from getting damaged, DNA is made of two polymer chains linked together, and this double strand naturally coils to form a double helix.
50
Q

what are the four types of bases on a nucleotide?

A

represented by the letters:
- T
- A
- G
- C

51
Q

describe carbohydrates:

A

carbohydrates = general term, refers to a number of different polymers and monomers.

  • we derive energy from carbohydrates.
  • they are all only made from carbon, hydrogen and oxygen.
  • the polymers (called polysaccharides) are things like starch, cellulose, and glycogen.
  • the monomers (monosaccharides or sugars) are things like glucose and fructose.
  • by combining the monomers together, we can make the polymers. by combining lots of glucose, we can make starch, for instance.

chemistry (9 decks)

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