C7: Organic Chemistry Flashcards
What is a hydrocarbon? [2]:
- Hydrocarbons are molecules made up of only hydrogen and carbon atoms.
- Hydrocarbons differ in their size, which can change the properties of the hydrocarbon.
Crude oil [4]:
- Crude oil is a mixture of lots of different compounds that are not chemically combined.
- Most of the compounds in crude oil are hydrocarbons.
- It is a non-renewable/ finite resource
- It is found in rocks and is used to produce other important chemicals
How is crude oil formed?
From compressing the fossilised remains of ancient plankton
What can crude oil be used to produce? [2]:
- Fuels
- Tarmac
Properties of long chain hydrocarbons [3]:
- Higher boiling points
- High viscosity (very viscous)
- They are less flammable
What is the general formula of alkanes?
CₙH₂ₙ₊₂
Properties of alkanes [5]:
- They are quite unreactive but they burn well
- They make good fuels
- Do NOT readily react with hydrogen water or the halogens
- No reaction with bromine water
- General formula CₙH₂ₙ₊₂
What are the 4 smallest alkanes?
- Methane
- Ethane
- Propane
- Butane
Fractional distillation in organic chemistry
[2]:
- The process of separating crude oil into groups of hydrocarbons with similar numbers of carbon atoms
(Long chain hydrocarbons into smaller ones) - We call these groups of hydrocarbons “fractions”
How does fractional distillation work?
Fractional distillation separates hydrocarbons using their different boiling points
Distillation process [5]:
- Crude oil is heated until it evaporates
- Crude oil vapour is put into a fractionating column from the bottom and rises upwards
- Long chain hydrocarbons condense at the bottom and are collected as liquids
- Short chain hydrocarbon have lower boiling points and so condense at lower temperatures near the top of the column
- The fractions are collected and processed to create end products
Products of fractional distillation [4]:
- Solvents
- Lubricants
- Polymers
- Detergents
What is the general formula of alkenes?
CₙH₂ₙ
The equation for the complete combustion of alkanes:
alkane + oxygen = carbon dioxide + water
What are 3 properties of Carbon Monoxide?
- Colourless
- Odourless
- Toxic
Burning hydrocarbons with oxygen [2]:
The combustion (burning) of hydrocarbons when there is a good air supply involve: -Energy release and the oxidation of carbon and hydrogen to create carbon dioxide and water
Burning Alkanes with lack of oxygen:
If alkanes are burned without enough oxygen, then carbon
monoxide can be created
Reactivity of alkenes [2]:
- Alkenes are more reactive than alkanes
- Alkenes react with orange-brown bromine water and turn it colourless
The demand for short-chain hydrocarbons [3]:
- There is a large supply of longer hydrocarbons
- However, there is a higher demand for small chain hydrocarbons because they have more uses
- Cracking helps to satisfy this demand
What are the products of cracking? [2]:
- Alkanes
- Alkenes
How can you test for Alkenes?
- Put them in orange-brown bromine water.
- If alkenes are present then the bromine water will become colourless
Cracking [definition]:
Breaking down long hydrocarbon chains into smaller more useful chains
Name two methods of cracking:
- Steam cracking
- Catalytic cracking
Catalytic cracking [2]:
- Vaporised hydrocarbons are passed over a hot catalyst
- The products include alkanes and alkenes
what is the functional group of alkenes?
C=C
c double bond
Steam cracking [2]:
- Vaporised heavy (long-chain) hydrocarbons are mixed with steam in a high-temperature environment
- The products include alkanes and alkenes
Saturated or not?
[2]:
- Alkanes are saturated
- Alkenes are unsaturated
What type of bonds do all alkenes contain?
a double bond
Why are alkenes unsaturated?
They contain 2 fewer hydrogens than alkanes (that have the same number of carbons) have
Properties of alkenes [6]:
- Decolourise bromine water
- contain only one C=C bond
- react with hydrogen water and the halogens by an addition reaction
- unsaturated
- During complete combustion, they produce water and carbon dioxide only
- More reactive than alkanes
What are the products of incomplete combustion?
[2]:
- Carbon monoxide
- Soot
What are the uses of alkenes?
[2]:
- Being combined to make polymers
- They are starting materials for chemicals like alcohols
What are the 4 shortest alkenes?
- Ethene
- Propene
- Butene
- Pentene
Why is there no methene?
Because there cannot be a C=C as there is only 1 carbon
What does a functional group do?
- A functional group is a group of atoms that determine (decide) how an organic compound will react
Addition reactions with alkenes [2]:
- Addition reactions are normal for alkenes.
- In these reactions, the carbon-carbon double bond opens up and allows new atoms to bond to the carbons.
What happens during an alkene addition reaction?
The carbon double-bond opens up
What is it called when a substance reacts with oxygen?
Combustions
What is the name of the process of adding hydrogen atoms across a carbon-carbon double bond?
Hydrogenation
Why do alkenes produce smoky flames when they react with oxygen in combustion?
- Because their combustion is more complete than alkane’s combustion
What do you need for alkenes to react with water?
[2]:
- The water to be in a gaseous state
- A phosphoric acid catalyst
What is the functional group of alcohols?
A hydroxyl group (OH)
What is the general formula of the alcohol homologous series?
CₙH₂ₙ₊₁OH
Properties of alcohols [4]:
- Mixes with water
- Can be oxidised to form a carboxylic acid
- Has a pH of 7
- Burns to release heat energy
Uses of alcohols [4]:
- Alcoholic drinks
- Fuels
- Mouthwashes
- Aftershaves
What are two methods of producing Ethanol?
- Fermentation
- Hydration
What are the conditions needed for fermentation?
[3]:
- A temperature between 25°C and 45°C
- Water but no oxygen
- Glucose solutions
(these are the optimum conditions for the enzymes of yeast)
How are aqueous solutions of ethanol produced?
When sugar solutions are fermented using yeast
Fermentation process [4]:
- The single-celled fungus yeast is added
- Air is kept out of the mixture and is kept at about 40°C for a few days
- The natural catalyst yeast ferments the sugars in the plant material to make carbon dioxide and ethanol
- Pure ethanol is extracted from the fermented mixture by fractional distillation
Hydration process [6]:
- Crude oil is extracted from the earth
- Crude oil undergoes fractional distillation
- The heavy fractions like bitumen are cracked to make a mixture of products including ethene
- Ethene is reacted with steam at 300°C, 60-70 atmospheres with a phosphoric acid catalyst
- The mixture is cooled so that ethanol condenses and can be run off
- Unreacted gases are recycled onto the reactor again
Fermentation is a …………………….. way of producing Ethanol
renewable
Hydration is a ……………………… way of producing ethanol
non-renewable
What happens when ethanol reacts with sodium? [2]:
- Bubbles of hydrogen gas are given off and colourless sodium ethoxide solution is left
- Sodium + Ethanol = Sodium ethoxide + hydrogen
Alcohol + water:
All the alcohols dissolved in water give colourless solutions with a pH of 7
What happens when alcohols react with an oxidising reagent?
They make a carboxylic acid
e.g ethanol will oxidise to make ethanoic acid
Rules when drawing the displayed formula [3]:
- Carbon always has 4 bonds
- Oxygen always has 2 bonds
- Hydrogen always has 1 bond
What is the functional group of Carboxylic acids?
COOH
What is the first 4 alcohols?
- Methanol
- Ethanol
- Propanol
- Butanol
What is the general formula of Carboxylic acids?
CₙH₂ₙ₊₁COOH
COOH is included on the n
What is the formula of Methanoic acid?
CHOOH
What is butanoic acid used for?
It is used as a natural repellant
What is the functional group of esters?
COOC
Esters [2]:
- They are made when a carboxylic acid reacts with an alcohol
- Esters have two-part names which ends in -oate
e. g ethyl ethanoate
Ester [definition]:
An organic compound made when an alcohol reacts with a carboxylic acid
Alkene [definition]:
An unsaturated hydrocarbon that contains at least one C=C
Alkane [definition]:
A saturated hydrocarbon
Alcohol [definition]:
An organic compound with an -OH functional group
Carboxylic acid [definition]:
An organic compound which is a weak acid and contains the -COOH functional group
Why are carboxylic acids described as weak?
They are only partially ionising and they give off relatively few hydrogen ions in comparison to stronger acids and have a higher pH than strong acids
Name the first 4 members of the homologous series of carboxylic acids:
- Methanoic acid
- Ethanoic acid
- Propanoic acid
- Butanoic acid
Properties of esters [2]:
- Smells sweet
- If insoluble, oily layer when added to water
Properties of carboxylic acid [4]:
- Efferveces with sodium carbonate to make carbon dioxide
- Litmus or universal indicator shows it is an acid
- pH probe shows that the value of 7
- Efferveces with a reactive metal to make hydrogen
Addition Polymerisation [3]:
- In addition polymerisation reactions, many small molecules (monomers) join together to form very large molecules (polymers)
- When monomers join together the double bonds open up and are replaced by single covalent bonds
- The polymer is made up of repeating pattern of atoms known as repeating units which is drawn in brackets
How are addition polymers produced?
When lots of small molecules called monomers join together
Uses of poly(ethene):
- Plastic bags
- Drink bottles
Uses of poly(propene):
- Crates
- Ropes
Monomers used to produce addition polymers contain…
double covalent bonds
Condensation polymerisation [2]:
- Involves monomers with two functional groups
- They usually lose small molecules such as water and so the reactions are called condensation reactions
Properties of addition polymers [5]:
- They are made from addition reactions and so are the only products
- Produced by unsaturated monomers that have a C=C
- Produced by only 1 type of monomer
- Non- biodegradable
- 100% atom economy
Properties of condensation polymers [4]:
- Made from two or more monomers with different functional groups
- A small molecule (such as water) is also produced when condensation polymers are produced
- Biodegradable
- Less than 100% atom economy
What happens during condensation polymerisation?
Monomers with 2 functional groups react and produce a polymer and water molecules
Amino acids are…
natural polymers
Amino acids [3]:
- Have two different functional groups in a molecule
- Amino acids react by condensation to polymerisation to produce polypeptides
- Different amino acids can be combined in the same chain to produce polypeptides or proteins
What is the amine functional group (peptide link)?
H₂N
What are some naturally occurring polymers? [4]:
- DNA
- Starch
- Cellulose
- Protein
What does DNA do? (chemistry definition):
DNA encodes genetic instructions for the development and functioning of living organisms and viruses
DNA structure (chem):
Most DNA molecules are two strands made from 4 different monomers called nucleotides in the form of a double helix
Each nucleotide contains…[3]:
- A base
- A phosphate
- A deoxyribose sugar
What are the 4 different bases in DNA?
- Guanine
- Cytosine
- Thymine
- Adenine
Starch and cellulose…
are both made from the monomer glucose
proteins are made from the monomer…
amino acids
‘sacc’ =
Sugar
Glucose structure:
It has a hexagonal ring structure
Starch info [3]:
- Made from around 1500 glucose molecules
- Has branched chains
- Energy store in plants
Glucose info [2]:
- Has the formula C₆H₁₂O₆
- It is a monosaccharide
Cellulose info [3]:
- Supplies support for plant structure
- Has straight chains
- made from around 10 000 glucose molecules
Why do heavy crude oil fractions not make good fuels? [3]:
- They have low volatility
- They do not ignite easily
- They have high boiling points
What type of reaction is cracking heavy hydrocarbons an example of?
Thermal decomposition
What type of reaction does the alkene functional group undergo?
Addition
what does the hydrogenation of alkenes require?
A nickel catalyst
