C6.2 - Organic Chemistry Flashcards
Hydrocarbon defintion
Compounds that contain hydrogen and carbon atoms ONLY.
Alkanes general formula
C n, H 2n+2
Saturated vs Unsaturated bonds
- Saturated bonds are SINGLE carbon-carbon covalent bonds
- Unsaturated bonds are DOUBLE carbon-carbon covalent bonds.
First four prefixes for Hydrocarbons
- Meth (1 carbon atoms)
- Eth (2 carbon atoms)
- Prop (3 carbon atoms)
- But (4 carbon atoms)
What happens during complete combustion? What about incomplete combustion?
Complete combustion:
- Carbon & Hydrogen are oxidised, both receiving oxygen.
- They become Carbon Dioxide and Water.
Incomplete combustion:
- Water is still made, but carbon monoxide is made.
- Some carbon atoms are not oxidised at all, released as carbon particles.
Why is incomplete combustion dangerous?
- It releases carbon monoxide.
- Carbon monoxide is toxic, and causes suffocation.
- Carbon monoxide displaces oxygen in the blood and deprives vital organs (e.g. brain and heart) of blood.
What is meant by a homologous series?
A homologous series is a family of hydrocarbons with similar chemical properties who share the same general formula.
Which (Alkanes/Alkenes) are saturated/Un-saturated?
- Alkanes are saturated (single bonds)
- Alkenes are unsaturated (contain at least one double bond)
Alkenes general formula
C n H 2n
How to draw the displayed formula for an Alkene
- Draw all the carbons in a straight line.
- Make one of the carbons double bonded.
- Make sure every carbon has four bonds (add hydrogens)
- Make sure you don’t add an extra hydrogen to the double bonded carbon.
- Check back to the formula to make sure it adds up.
What are functional groups?
Functional groups are atoms, groups of atoms, or types of bonds in a molecule that are responsible for the characteristic reactions of the substance.
What are addition reactions?
When atoms or groups of atoms combine with a molecule to form a larger molecule with no other product.
How to test for an alkene
- Test using orange-brown bromine water.
- When bromine is added to an alkene, it turns into a colourless compounds.
- Ethene + Bromine –> Dibromoethane (Addition reaction)
How can we convert an alkene into an alkane?
Alkenes can undergo addition reactions with hydrogen in the presence of a nickel catalyst to form alkanes.
Alcohol function group
-OH
Alcohol general formula
C n H 2n+1 OH
How to draw the displayed formula for an alcohol
- Draw the carbons, then add the hydrogens to the left hand side onward.
- Add the functional group (-O-H) to the end.
How do alcohols form carboxylic acids?
- By reacting an alcohol with an oxidising agent (oxidising it) we can make a carboxylic acid.
- Take the alcohol, add the oxidising agent, and add dilute sulfuric acid, and gently warm it.
- A colour change should be observed.
Functional group of carboxylic acid
-COOH
- Acids end in -anoic acid
General formula for carboxylic acid
C n H 2n+1 COOH
How do carboxylic acids react (Metals, alkalis, carbonates)? Are they weak/strong acids?
- They are weak acids.
- They react with METALS to produce salt and hydrogen.
- They react with ALKALIS and bases to produce salt and water.
- They react with CARBONATES to produce salt, water and carbon dioxide.
Names for the salts formed from carboxylic acid
- They have the ending -oate
- Ethanoic Acid + Sodium Carbonate –> Sodium Ethanoate + Water + Carbon Dioxide
How does crude oil (fossil fuel) form?
- Things that lived millions of years ago die, and they become buried deep into the seabed.
- They eventually turn into crude oil.
- This is a long and slow process, so crude oil is non-renewable.
What is crude oil made of?
A mixture of many different hydrocarbons.
How do we separate crude oil?
- Fractional distillation.
How does fractional distillation work?
- Hydrocarbons have different boiling points.
- A fractionating column has different temperature gradients (hottest at bottom).
- As vapours rise they condense and run off to be collected.
- Each fraction contains substances with similar boiling points.
Temperature gradient in a fractionating column
25 degrees (lowest)
350 degrees (highest)
Different substances collected from a fractionating column (lowest to highest)
LOWEST TEMP
- Bitumen (very top)
- Fuel oil
- Heating oil
- Diesel
- Paraffin
- Petrol
- LPG (very bottom)
HIGHEST TEMP
What determines the boiling point of a hydrocarbon?
The more carbon atoms, the longer the molecule, so the stronger the intermolecular forces are (so a higher boiling point).
What bonds hold atoms in hydrocarbons together?
- Covalent bonds, which are stronger than intermolecular forces.
- When boiled, the intermolecular forces between molecules are broken, not the covalent bonds.
Cracking - What does it do, how does it work
- Cracking converts large hydrocarbon molecules into smaller more useful hydrocarbon molecules.
- It needs; A catalyst (alumina or silica), High Temperature (600c-700c)
- Cracking helps to match supply to demand by breaking the covalent bonds between the atoms to make smaller hydrocarbons.
- E.g. Octane –> Hexane + Ethene
Why are large hydrocarbons less useful? Why is cracking so important?
- They do not flow easily and are hard to ignite (low flammability).
- 90 percent of crude oil is used to produce fuels (e.g. petrol and diesel), so it allows us to match supply to demand.
Plastic is a….
Polymer
Types of polymers
- Addition polymers
- Biological polymers
- Condensation polymers
How to make addition polymers
- Addition polymers undergo an addition reaction when they join together. They can do this as they contain a C=C bond.
- The monomers are alkenes.
- To make these, you need high pressure and a catalyst.
How to find the name of a polymer
INPUT monomer name
OUTPUT poly + monomer name
How to draw the addition polymer of a monomer
- Redraw the monomer BUT:
- Change the double bond between the carbons to a single bond.
- Draw square brackets around them.
- Draw bonds sticking out of the sides of the brackets like arms.
- Put the letter ‘n’ in the bottom right.
How many amino acids are there that naturally occur in the body?
20
What is a condensation reaction?
- Two molecules react together to form one larger molecule, and one smaller molecule, which is often water.
- They don’t require a catalyst, and work at room temp/pressure.
- The monomers for condensation polymers need two functional groups.
- Carboxylic acid + Alcohol –> Ester (Salt) + Water
Two functional groups of amino acids
- Amino group - NH2
- Carboxyl group - COOH
The monomers are joined by an amide group. -CONH-
What is polyester? What is it made up of? What does it make when it joins together? What are its uses?
- It is an artificial condensation polymer.
- Made from carboxylic acid with 2 carboxyl groups.
- An alcohol with two hydroxyl groups.
- When they join together, they form many ester groups (hence the name).
- Uses include clothing/drink bottles.
What is polyamide?
- It is an artificial condensation polymer.
- Made from carboxylic acid with 2 carboxyl groups.
- Amine with two amino groups.
- They form many amide groups when formed (hence the name).
- They form nylon (an example).
What does a fuel cell do?
- A fuel cell produces electricity through a chemical reaction between a fuel and oxygen but without combustion occurring.
Pros of fuel cells
- They only require oxygen and hydrogen, which are abundant and easy to source.
- They don’t produce any waste (e.g. carbon dioxide or other pollutants)
- Fuel cells are relatively simple devices, so they last longer than batteries do, and they’re less pollution to dispose of.
Downside of fuel cells
- Hydrogen is a gas, so it takes up much more volume to store than fossil fuels/batteries.
- They are explosive when mixed with air, so storing it is difficult.
- Making the hydrogen fuel in the first place requires energy, which often comes from fossil fuels.
Describe how fuel cells work.
- Hydrogen reacts with oxygen in an exothermic reaction to produce water vapour.
- Hydrogen molecules lose electrons and become hydrogen ions.
- Hydrogen ions combine with oxygen at the other side to form water vapour.
How does a chemical cell work?
- Exothermic reactions in the cell develop a potential difference/voltage between the two ends.
- When the cell is connected to an electrical circuit, this potential difference drives a current, which flows through the cell and the components of the circuit.
- This continues until one of the reactants is used up, so a potential difference can no longer be produced.
What is a ‘diol’?
An alcohol with two functional groups (double OH)
What is ‘hydroxyl’?
Hydroxyl is alcohol functional group -OH
What is ‘carboxyl’?
Carboxyl is carboxylic acid functional group -COOH
