organic chemistry Flashcards
volatile
evaporates very easily, eg: petrol
viscosity
a liquid that doesn’t flow easily, ‘thick,’ eg: honey, ketchup, oil
Test for alkenes
Bromine water decolourises from orange.
What is a hydrocarbon?
A compound containing hydrogen and carbon only.
Q: Why is oxygen/ nitrogen a gas at room temperature?
They are small molecules. They have very weak intermolecular forces so less energy is needed to break these weak forces and separate these molecules.
Describe the properties of Diamond (the four C’s- Cut, Clarity, Carat and Colour)
- Each carbon atom forms four covalent bonds
- A tetrahedral shape is formed
- No delocalised electrons so diamond does not conduct heat/ electricity
- Diamond is transparent
- Diamond is extremely hard
- There are no layers
- Diamond is brittle
Describe the properties of graphite
- Each carbon atom forms 3 covalent bonds
- Therefore 1 electron is delocalised and can conduct heat/ electricity
- Graphite is very soft because the forces holding each layer are weak so the layers can slide over which is why it is a good lubricant.
- In the layers are covalent bonds.
Give one use of graphite
pencil lead
Why is graphite a good lubricant?
The forces holding each layer are weak so the layers can slide over.
What is the difference between graphene and graphite?
Graphene is made up of a single layer of carbon atoms whereas graphite is made up of many layers.
Describe the properties of fullerenes.
- They are molecules of carbon atoms with hollow shapes
- Their structures are based on hexagonal rings of carbon atoms joined by covalent bonds
- Some fullerences include rings with five or seven carbon atoms
- very good lubricant
- can be used to strengthen tennis rackets
What is buckminsterfullerene used for?
It is used for drug delivery to target areas of the body.
What are two examples of fullerences?
Buckminsterfullerene and nanotubes.
Describe the properties of buckminsterfullerene
- First fullerene to be discovered
- It molecules are made up of 60 carbon atoms joined together by strong covalent bonds
- Molecules of C60 are spherical
- There are weak intermolecular forces between molecules of buckminsterfullerene. These need little energy to overcome so buckminsterfullerene is slippery and has a low melting point
Uses of nanoparticles and why?
- Because nanoparticles are small, they can give greater coverage so more particles can cover the gaps and will last longer- cosmetics
- Nanoparticles are used in computer components: microchips
- Nanoparticles are used as catalysts as they increase the rate of chemical reactions
How big are nanoparticles?
1nm - 100 nm
homologous series
- have similar properties
- all react in a similar way
homologous series
- have similar properties
- all react in a similar way
general formula of alkanes
CnH2n+2
Key features of alkanes
- saturate compounds: every carbon atom has full single covalent bonds
As the length of the carbon chain increases,
- the boiling point increases
- less volatile
- more viscous (thick and sticky)
- less flammable
What are the main uses of hydrocarbons?
- ## fuel, because they release a lot of energy when they are burned with oxygen
complete combustion (enough oxygen)
hydrocarbon + oxygen –> carbon dioxide + water
hydrocarbon and oxygen are being oxidised
What is the significance of shorter hydrocarbons?
- they have the lowest boiling points making them the most volatile and flammable, makes them great fuels.
using a hydrocarbon as a fuel
combustion
combustion
releases a lot of energy in the process
crude oil
- fossil fuel
- a mixture containing nearly only hydrocarbons
- formed from the remains of dead plants and animals, particularly plankton died billions of years ago. High temperatures and pressures under the ground turned the organic biomass into crude oil. The crude oil was soaked into the rocks and was stored for years.
- finite resource
- extract and use it at the same rate- will run out completely
renewable
Will not run out because it is replenished.
non-renewable
will run out because it is not replenished
Fractional distillation
1, Feed the oil into a chamber until it turns into a vapour
2, Pass the vapour into a fractionating column which has a temperature gradient (hot at the bottom and cold at the top)
3, The gases will rise up the column and as soon as they reach a region with a lower temperature than their boiling point, they will condense into a liquid.
4, The long-chain hydrocarbons have higher boiling points than the short-chain hydrocarbons so will quickly condense into a liquid and be piped out of the column. (eg: bitumen- roads, heavy fuel oil can heating oil, fuel oil, lubricating oil).
5, The shorter-chain hydrocarbons will rise up the column until they reach a cooler temperature until they condense into a liquid.
6, LPG- some remain as a gas
7, Longer chain hydrocarbons can be cracked to produce shorter-chain hydrocarbons
What are petrochemicals (substances from crude oil) used for?
can be used as feedstock for the petrochemical industry to make solvents, lubricants, polymers and detergents.
Longer-chain hydrocarbons are
thick,viscous liquids, making them comparitively less useful
cracking
It is a thermal decomposition reaction.
Catalytic cracking
- Heat our long-chain hydrocarbons and vapourise them.
- Pass the hydrocarbon vapour over the hot powdered aluminium oxide (catalyst) and and the long-hydrocarbons split apart into two smaller hydrocarbons.
steam cracking
- Heat our long-chain hydrocarbons and vapourise them.
- Mix them with steam and then heat them to a very high temperature
- This causes the long hydrocarbon chains to split apart into shorter ones
alkenes can be used
- to make polymers
- as the starting materials for producing a lot of other chemicals
alkenes are
a homologous series
difference between alkanes and alkenes
alkenes are unsaturated and alkanes are saturated
alkenes are more reactive than alkanes
If we add bromine water to alkene solution, it will decolourise
alkenes can be added together to make polymers (double bond can break to form two or more bonds)
Alkenes contain
- at least one carbon double bond
Hydrogenation of alkenes
- alkene chemically reacts with hydrogen with a nickel catalyst to produce an alkane (saturated)
- hydrogenation is used to produce margarine and chocolates.
- 150 degrees Celsius
- two hydro
Alkene with water- hydration
- water in form of steam
ethene + steam : high temperatures and a catalyst. Phosphoric acid catalyst and temperature of around 300 degrees Celsius and a pressure of around 60-70 atmospheres - ethene+ steam –> ethanol
- used a lot in industrial processes and alcoholic drinks
- It is a reversible reaction. To increase the yield of ethanol, any unreacted ethene and steam are passed back through the catalyst.
- advantage: the reaction produces a high yield of ethanol
- disadvantage: the reaction requires a high temperature (in other words- a lot of energy)
- disadvantage: the ethene from this reaction comes from crude oil and is non-renewable
combusting alkanes and alkenes
- carbon dioxide and water
- combusting an alkene also produces unburnt carbon particles. That is because of incomplete combustions.
alkenes burn in air with a
smoky flame
alkenes and halogens
- alkenes react quite rapidly with halogens
What are the uses of alcohols?
- fuels
- solvents
- alcoholic drinks
The alcohols are a
homologous series (same functional group)
Fermentation of sugar - alcohol
- start with a sugar solution such as glucose and mix this with yeast
- The yeast converts the sugar solution to a solution of ethanol. Carbon dioxide gas is also produced.
- the temperature should be around 30 degrees Celsius
- the reaction must take place in anaerobic conditions (without oxygen)
- advantage: the low temperature means that the reaction does not require a lot of energy
- advantage: the sugar for this reaction comes from plants and is therefore renewable
- disadvantage: the product is an aqueous solution of ethanol (ethanol dissolved in water). We then need to purify the ethanol by distillation and that requires energy.
- -to separate water and ethanol- use fractional distillation: take the mixture of ethanol and water and place it in a heating flask. As it is heated up with a bunsen burner, the ethanol will boil first, evaporate up through the column and condense into a separate beaker.
Are alcohols soluble in water?
Yes, and they form neutral solutions
As the number of carbon atoms for alcohols increases,
the solubility decreases
alcohol + sodium (eg: ethanol)
ethanol + sodium –> sodium ethoxide + hydrogen
- bubbles of hydrogen are produced
ethanol reacting with an oxidising agent
- alcohol reacts with oxidising agent to produce carboxylic acid and water
- a good example of an oxidising agent is acidified potassium dichromate
- alcohol –> carboxylic acid + water
oxidising agent
Combustion of alcohols in air
- alcohol + oxygen –> carbon dioxide + water
dissolving carboxylic acids in water
- in water, they are weak acids
- ethanoic acid (aq) CH3COOH⇌ CH3COO- (aq)ethanoate ion + H+ (aq)
- ethanoic acid is ionising to produce the ethanoate ion and H+
- reversible reaction
- the ethanoate ion and H+ can recombine to form ethanoic acid
- carboxylic acids only partially ionise in aqueous solution because they are weak acids.
- Carboxylic acids have a higher pH than a strong acid such as hydrochloric acid
carboxylic acids reacting with metal carbonates
- produce a salt, water and carbon dioxide
carboxylic acids reaction
- react with metal carbonates
- react with alcohol
Esters
When we react a carboxylic acid with an alcohol, we make a molecule called an ester and we also make water.
Why are esters useful?
- esters have a pleasant smell so are used a lot in foods
ethanoic acid + ethanol
- ethyl ethanoate
- requires sulfuric acid as a catalyst
- reversible reaction
Polymer
-It is made of joining together monomers
Addition polymers
- monomers are alkenes
- the monomer has a double carbon to carbon bond but the polymer has single carbon to carbon bonds
- the repeating unit has the same atoms as the monomer because no other molecule is formed in the reaction
- all the atoms in the monomer end up in the polymer
- the repeating unit does not contain a double bond
condensation polymers
- also made from monomers
- the monomers are not alkenes
- when these monomers react, we lose small molecules such as water
- we start with two different monomers
- ## each monomer has two of the same functional groups
Thousands of monomers can join together to make a polymer-. What is this called?
A polyester
Amino acid molecules have two different functional groups:
- amine group- H2N
- carboxylic acid group COOH
What can amino acid molecules react to form?
- condensation polymers because they have two different functional groups
- eg: two glycine molecules reacting together will produce a polymer and a molecule of water
- can also react another glycine molecule onto the end- make another molecule of water
- can continue adding glycine molecules to form a polymer
- glycine molecules reacting to form a polymer: because the polymer is only made from one type of amino acid- polypeptide
If a polymer is made up of different amino acids it is called
a protein
DNA consists of
two polymer chains made from monomers called nucleotides
DNA is a
double helix
More naturally occurring polymers
- proteins: polymers of amino acids
- starch: polymer of glucose
- cellulose : polymer of glucose
- however, in starch and cellulose, the glucose molecules are arranged in slightly different ways.
Hydration of ethene advantages
- quick
- product is pure
Fermentation
- glucose –> ethanol and carbon dioxide
(yeast and no air)
C6H12O6 –> 2C2H5OH + 3CO2
disadvantage of hydration of ethene
- expensive
- used up crude oil
Advantages of fermentation
- cheap
- renewable
- carbon neutral
Disadvantages of fermentation
- slow
- product is impure
Other reactions of alcohols
oxidation is also the
removal of hydrogen
making esters catalyst
- concentrated sulfuric acid
- concentrated phosphoric acid
uses of esters
- perfumes (very volatile)
- solvents (dissolve in esters)
- flavourings (sweet smell)
