T6 - Organic Chemistry Flashcards
What is a hydrocarbon?
A molecule consisting of only carbon and hydrogen.
Alkanes
Most basic type of organic molecule. The general formula for one is CₙH₂ₙ₋₂.
Alkenes
Similar to alkanes except have a double carbon bond.
Alcohol
Has a single carbon bond, also has a OH bonded to a carbon.
Name all 7 types of reactions
Polymerisation, Addition, Hydrolysis, Substitution, Reduction, Oxidation and Eliminations
What is polymerisation?
Joining smaller monomers together to form a very long chain
What is addition?
Joining molecules together to form longer ones
What is hydrolysis?
Splitting a molecule into 2 using a OH anion or H cation from a water molecule
What is substitution?
Replacing one atom with another on a molecule
What is reduction?
When a species gains electrons in a reaction
What is oxidation?
When a species loses electrons in a reaction
What is elimination?
Some atoms break away from a larger molecule
What is a chemical mechanism?
Showing the movement of electrons during a chemical reaction
What is radical substitution?
Used in reacting halogens to alkanes to make halogenoalkanes
What is electrophilic addition?
Used in adding halogens and hydrogen halides to alkenes to make halogenoalkanes
What are the 3 types of structural isomers
- Chain, 2. Positional, 3. Functional group
What is a structural isomer?
The same molecular formula but a different structural formula
What are chain isomers?
Same molecular formula but different arrangement of the carbon skeleton
What are positional isomers?
Same molecular formula but different position of the functional group on the carbon skeleton
What are functional group isomers?
Same molecular formula but different functional group
What are the two types of bond fission?
Homolytic and heterolytic
What is bond fission?
The breaking of a covalent bond
What is heterolytic fission?
When the covalent bond breaks the 2 electrons are distributed unequally all to one element to from a cation and an anion. A double headed arrow shows the movement of a pair of electrons.
What is homolytic fission?
When the covalent bond breaks the pair of electrons in the bond are shared equally to form 2 uncharged radicals. 2 one-headed arrow is used to show movement of electrons. The dot on the element means there is an unpaired electron on the atom
What are the 3 stages of free radical chain reactions
Initiation, Propagation, Termination
Name some of the substances found in crude oil that can be fractionally distilled.
Diesel Oil, Fuel Oil, Kerosine, Gas, Petrol, Bitumen
What are the 2 types of cracking?
Thermal cracking and catalytic cracking
What is cracking and why do we do it?
Cracking is breaking long chain alkanes into shorter hydrocarbons. We do it because heavier fractions (long alkanes) are in low demand and lighter fractions like petrol are higher demand therefore more valuble.
What are the conditions needed for thermal cracking?
1000 degrees celcius and 70atm of pressure
What are the main products from thermal cracking?
Alkenes
What are the conditions needed for catalytic cracking?
450 degrees celcius and slight pressure, and a zeolite catalyst to help lower the temperature needed
Why are zeolite catalysts used in catalytic cracking?
It lowers the temperatures and pressure needed for cracking to occur, which lowers cost and speeds up the process
What are the products of catalytic cracking?
Mainly aromatic hydrocarbons, that are useful for fuels for vechiles
What is produced during the complete combustion of alkanes with plentiful oxygen?
Carbon dioxide and Water
What is produced during the incomplete combustion of alkanes with limited oxygen?
Carbon monoxide and water
What is produced during the incomplete combustion of alkanes with very limited oxygen?
Carbon (soot) and water
Why is carbon monoxide bad and how can we remove it?
Carbon monoxide is poisonous as it bonds to haemoglobin in the blood instead of oxygen bonding, which disables the blood from delivering oxygen around the body and heart. We can remove it with a catalytic converter.
Why is soot bad?
It can get into the lungs and cause breathing problems or lung cancer, make buildings dirty and can clog up engines
Acid rain
Burning fossil fuels can release sulfur dioxide and oxides of nitrogen which contribute to acid rain
What can acid rain do?
Acid rain can cause damage to plants, kill fish and cause erosion of buildings
How does acid rain form from sulfur based impurities?
Some fossil fuels can contain sulfur based impurities, so when burned is released into the air and reacts with oxygen to produce sulfur dioxide. Sulfur dioxide is an acidic gas, which then reacts with water in the atmosphere to form sulfuric acid which falls as acid rain
How does acid rain form from nitrogen?
Oxides of nitrogen are produced when nitrogen and and oxygen from the air are heated in the engine and react. The oxides of nitrogen then dissolve in the water in the atmosphere to form nitric acid which falls as acid rain
Where are catalytic converters found and what do they do?
Catalytic converters are found mainly in vehicles and help to reduce the amount of unburnt hydrocarbons and oxides of nitrogen going into the atmosphere
Why do people tend to try steal catalytic converters?
They contain expensive metals like platinum, rhodium and iridium metals
What gases do catalytic converter convert and what are then converted into?
Harmful gases : Carbon monoxide, nitrogen oxides and unburnt hydrocarbons
Less harmful gases: Water vapour, nitrogen and carbon dioxide
Name 3 biofuels
Bioethanol, biodiesel and biogas
How is bioethanol made?
Sugar from sugar cane is fermented to produced alcohols (ethanol) which can be used as a renewable fuel
How is biodiesel made?
Made from refining oils and fats
How is biogas made?
Make from break down of organic matter
Advantages of biofuels?
- Biofuels are renewable so they are a more sustainable than crude oil
- Biofuels produce carbon dioxide when they are burnt however they are classed as carbon neutral as the carbon dioxide is absorbed by the plants when its growing
Disadvantages of biofuels?
- Expensive to convert existing petrol engines to take fuels with a higher concentration of ethanol
- Land that could have been used to grow food is being used to make fuel. This could cause food shortages in countries that grow sugar cane
Why are alkenes fairly reactive?
Double bonds have a high electron density and this makes alkenes fairly reactive
Why is there restricted rotation in alkenes?
The carbons first bond is the sigma bond (which contains 2 electrons), and also has 2 sigma bonds between 2 hydrogens, leaving one delocalised electron in the p orbital. These p orbitals overlap, so the delocalised electrons can then be found in pi cloud of electron density. Since a p orbital is dumbbell shaped, there are pi clouds on either side, so it cannot rotate.
