SC22-24 Organic Chemistry Flashcards
Define hydrocarbon
- Contains hydrogen and carbon
- **only **
Define homologous series
‘Family’ of organic compounds that have the same functional group and similar chemical properties
Define functional group
Atom or group of atoms that are responsible for the characteristics and reactions of an organic compounds
What are alkanes?
A homologous series with the general formula of CnH2n+2
Name the first four alkanes
- methane
- ethane
- propane
- butane
Alkanes contain saturated bonds. What does the term saturated mean?
They only contain single bonds between the carbons
What is the molecular formula for methane?
CH4
What is the molecular formula for ethane?
C2H6
What is the molecular formula for propane?
C3H8
What is the molecular formula for butane?
C4H10
What are alkenes?
Homologous series that contain an unsaturated bond and have a chemical formula of CNH2N
What does the term unsaturated bond mean?
Containing a double carbon bond
How can alkenes make more bonds?
By opening up the double C bond
What are addition reactions?
Reactions wherein one molecule combines with another, forming a larger molecule and no other products
Ethene and Bromine are in an addition reaction. What is the product formed?
1,2 diobromoethane
Why are alkenes more reactive than alkanes?
Their double bond allows them to merge with other molecules, whereas alkanes don’t have a double bond which limits their reactivity
Define isomer
Chemicals that have the same molecular formula but different arrangements of atoms
Give an example of an alkene that has isomers
Butene:
- but-1-ene
- but-2-ene
Where is the double bond placed in but-1-ene?
On the first carbon bond
Where is the double bond placed on but-2-ene?
On the second carbon
When considering isomers, what side of the chain do we begin counting from?
Take the shortest route: this could be going from right to left or from left to right
How can we test for a difference between alkanes and alkenes?
- shaking bromine water with the two solutions
- alkenes will decolourise the solution, changing it from orange yellow to colourless
- alkanes will result in no change, which means the solution remain orange-yellow
Which of the two homologous groups undergo complete combustion?
Alkanes and Alkenes
Which of the two homologous groups undergo incomplete combustion?
Alkenes
What are the products formed from complete combustion?
Carbon dioxide and water
What is the general formula of alcohols?
CnH2n+1OH
What is the functional group of alcohols?
hydroxyl group (OH)
State the chemical properties of alcohols
- produce C02 and H20 in a complete combustion reaction
- can be oxidised to form carboxylic acids
- react with reactive materials, forming H20 as one of the products
What are the uses of alcohol?
- cosmetics
- medical drugs
- varnishes
- methanol and ethanol used as fuels
Name the first four alcohols
- methanol
- ethanol
- propanol
- butanol
What is the molecular formula for ethene?
C2H4
What is the molecular formula for propene?
C3H6
What is the molecular formula for butene?
C4H8
What is the molecular formula for pentene?
C5H10
What is the main alcohol found in alcoholic drinks?
Ethanol
How is ethanol produced?
Through fermentation
How is ethanol concentrated?
fractional distillation
Write a word equation for fermentation
Glucose –> ethanol + carbon dioxide
What is the formula for ethanol?
C2H50H
Where do the enzymes for fermentation come from?
From yeast cells
State a quick overview of what happens in fermentation
Sugar or starch is dissolved in water and yeast is added
What do the enzymes do in fermentation?
They break down the sugars to alcohol
What does chemically oxidised alcohol produce?
Carboxylic acids
Why must there be an air lock to ferment the ethanol?
To keep the oxygen out as yeast fermentation is a type of anaerobic respiration
What is the highest concentration of alcohol produced by yeast fermentation?
15%
What is used to produce a more concentrated solution of ethanol?
Fractional distillation
Explain how fractional distillation is used to produce more concentrated solutions of alcohol such as ethanol
- The water and ethanol solution are heated
- Ethanol evaporates first as it has a lower boiling point than water, cools then condenses
- The water left evaporates, cools then condenses
State the first four alcohols
- Methanol
- Ethanol
- Propanol
- Butanol
State the formula for methanol
CH3OH
State the formula for propanol
C3H7OH
State the formula for butanol
C4H9OH
Write a balanced equation for the formation of ethanol from carbohydrates
C6H12O6 + enzymes → 2CO2 + 2C2H5OH
State the chemical properties of alcohol
- Produce carbon dioxide and water during complete combustion
- can be oxidised to form carboxylic acids
- react with reactive metals, forming water as one of the products
Why do all alcohols have similar chemical properties?
They all have the same functional group
Name the first four carboxylic acids
- Methanoic acid
- Ethanoic acid
- Propanoic acid
- Butanoic acid
What is the functional group of carboxylic acids?
Carboxyl- COOH
What is the general formula of a carboxylic acid?
Cn-1H2n+1COOH
State the formula for methanoic acid
HCOOH
State the formula for Ethanoic acid
CH3COOH
State the formula for Propanoic acid
C2H5COOH
State the formula for Butanoic acid
C3H6COOH
State some chemical properties of carboxylic acids
- form solutions with pH less than 7
- react with metals to form a salt and hydrogen
- react with bases to form salt and water
- react with carbonate to form a salt, water and carbon dioxide
Define polymer
A long chain molecule made by joining many smaller chain molecules together
Define monomer
A small molecule that can join molecules like itself to form a polymer
Define addition polymerisation
A type of polymerisation in which the monomers add onto each other and no small molecule is eliminated. It only occurs with monomers that contain the double C bond
How do ethene molecules join together to form poly(ethene)?
- They lose the carbon double bond
- which then transfers to the sides of each of the carbons
- to form a repeating unit
How do alkenes in general undergo addition polymerisation?
They lose their double carbon bond
Name the folowing monomers for the biological polymers:
a) DNA
b) starch
c) protein
a) nucelotides
b) glucose
c) amino acids
How is the name of the polymer deduced?
poly(monomer)
How do we deduce the structure of a monomer from the polymer?
- Identify the repeating unit in the polymer
- Change the single bond in the repeat unit to a double bond in the monomer
- Remove the bond from each end of the repeat unit and the subscript n (which can be placed in front of the monomer)
How do we deduce the structure of a monomer from its polymer?
- Draw a repeating unit (monomer without double carbon bond)
- Add a bond to the end of each repeating unit
- The bonds must extend out of the square brackets
- small subscript n written on the bottom right hand side
What does the small subscript n in a repeating unit stand for?
Indicates a large number of repeat units
What are the properties of poly (ethene)?
- flexible
- cheap
- good insulator
What are the properties of poly(propene)?
- flexible
- shatterproof
- strong
What are the uses of poly(ethene)?
- plastic bags and bottles
- cling film
What are the uses of poly(propene)?
- buckets
- food packaging
- ropes
What are the properties of poly(chloroethene)?
- tough
- good insulator
- rigid
- flexible
What are the uses of poly(chloroethene)?
- window frames
- gutters
- pipes
What are the properties of poly(tetrafluoroethene)?
- tough
- slippery
What are the uses of poly(tetrafluoroethene)?
- nonstick coating for frying pans
- burette taps
- stain proof clothing
Define condensation polymerisation
A small molecule is formed as a byproduct each time a bond forms between two monomers
What products are produced during the condensation reaction between an alcohol and a carboxylic acid?
Esters and water
What particular position must the two monomers be whilst reacting under condensation polymerisation?
- functional monomers must be facing each other so that the ester link can be formed between the carbon and oxygen and water can be removed
What are the problems with making polymers?
- made using crude oil, which is a finite and non renewable resource
- can have a damaging impact on the environment if extraction and transportation goes wrong
What are the problems with the disposal of polymers?
- cannot bidegrade
- harms environment if not properly disposed
- can release toxic flames if incinerated
What are the advantages of recycling polymers?
- reduces litter
- reduces the release of toxic gases in the environment from burning them
- allows raw materials to last longer
What are the disadvantages of recycling polymers?
- costs money and energy
- time consuming
Describe how to recycle polymers
- Collecting and sorting waste into different types
- disposing unrecyclable waste
- cleaning and grinding polymers into chips
- purifying chips
- melting chippings to process into new products
- codes and symbols are used to make sorting polymers easier