Organic Chemistry Flashcards
What is covalent bonding?
The strong electrostatic force of attraction between the nuclei of bonding atoms and shared common electrons
Does covalent binding only occur in metals or non-metals?
Only non-metals
What shell of electrons do you draw when drawing dot-and-cross diagrams?
Only the outer shell
What is a homologous series?
A series of molecules in which:
- all have the same general formula
- all share similar chemical properties (e.g boiling point)
- all follow trends in physical properties (e.g colour and viscosity)
What is crude oil?
A mixture of hydrocarbons
What is a mixture?
Two or more substances that aren’t chemically bonded together
What is a hydrocarbon?
A compound consisting of only hydrogen and carbon
Describe the process of the fractional distillation of crude oil
- Crude oil is heated and evaporates into a gas
- Vapour passes into the fractionating column, in which the temperature decreases as you travel up it
- Fractions collect where the temperature in the fractionating column is equal to or below their boiling point and they condense
- Fractions are then piped out of the fractionating column as liquids (or gases if its refinery gas)
What are the six gases in order of which they come out of the fractionating column?
Bitumen, fuel oil, diesel, kerosene, gasoline, refinery gas
What is bitumen used for?
Tar
What is fuel oil used for?
Fuel for ships
What is diesel used for?
Fuel for cars/lorries/trains
What is kerosene used for?
Fuel for planes
What is gasoline used for?
Fuel for cars
What is refinery gas used for?
Fuel for household cooking and heating
What is the trend in fractions in terms of size of molecules?
Size of molecule decreases as you go up the fractionating column
What is the trend in fractions in terms of boiling point?
Boiling point decreases as you go up the fractionating column
What is the trend in fractions in terms of viscosity?
Viscosity of fraction decreases as you go up the fractionating column
What is the trend in fractions in terms of colour?
Colour of fraction gets lighter as you go up the fractionating column
What is a fuel?
A fuel is a substance that, when burned, releases heat energy
Complete combustion
When a substance burns in sufficient oxygen
Incomplete combustion
When a substance burns in insufficient oxygen
Word equation for the complete combustion of alkanes
Alkane + oxygen => carbon dioxide + water
Word equations for the incomplete combustion of hydrocarbons
Hydrocarbon + oxygen => carbon + water OR hydrocarbon + oxygen => carbon monoxide + water
Why is carbon monoxide poisonous?
When carbon monoxide produced from incomplete combustion is inhaled into the lungs, the haemoglobin binds to it in preference to oxygen; it irreversibly binds to the haemoglobin producing carboxyhemoglobin. This therefore reduces the blood’s capacity to transport oxygen around the body
How does burning fossil fuels lead to the production of sulphuric acid to cause acid rain?
- fossil fuels contain sulfur as an impurity
- when fossil fuels are burned, the oxygen in the air reacts with the sulphur to produce sulfur dioxide gas
- when the sulfur dioxide passes into the atmosphere,it dissolves into rainwater and makes it become more acidic
- this causes acid rain
How do car engines produce nitrogen oxides and lead to acid rain?
- nitrogen is an inert element that is gas at room temp.
- it makes up 78% of the air around us
- however in car engines, temperatures reach enough for the nitrogen to react with oxygen in the air and produce nitrogen oxides
- these oxides of nitrogen are also acidic, which dissolve into rainwater and make it more acidic and cause acid rain
What is cracking?
A process in which long-chain alkanes are converted into short chain alkanes and Alkenes
Why is cracking necessary, in terms of supply and demand?
- the supply of long-chain alkanes is higher than demand, however the supply of alkenes and short chain alkanes is lower than demand
- therefore , cracking is needed to satisfy supply and demand for shorter chain alkanes and alkenes
Explain how catalytic cracking works
- long chain alkanes are evaporated to gas form
- then they are passed over a hot catalyst (either silica or alumina) at 600-700ºC
- as a result of thermal decomposition, the long-chain alkanes break down to form short chain alkanes and alkenes are produced such as petrol
What is a saturated hydrocarbon?
A hydrocarbon that only contains single bonds between the carbon and hydrogens in its molecule
What is an unsaturated hydrocarbon?
A hydrocarbon that contains at least one carbon-carbon double bond in its molecule
What is silica made out of?
Silicon dioxide
What is alumina made out of?
Aluminium oxide
What is an alkane?
A homologous series of saturated hydrocarbons with the general formula of CnH2n+2
What is the general formula of the alkanes?
CnH2n+2
Molecular formula of methane
CH4
Structural formula of methane
CH4
Empirical formula of methane
CH4
Molecular formula of ethane
C2H6
Structural formula of ethane
CH3-CH3
Empirical formula of ethane
CH3
Molecular formula for propane
C3H8
Structural formula for propane
CH3-CH2-CH3
Empirical formula for propane
C3H8
Molecular formula of butane
C4H10
Structural formula for butane
CH3-CH2-CH2-CH3
Empirical formula for butane
C2H5
Molecular formula for pentane
C5H12
Structural formula for pentane
CH3-CH2-CH2-CH2-CH3
Empirical formula for pentane
C5H12
What is a structural isomer?
Molecules with the same molecular formula but different structural formula
What is an alkene?
A homologous series of unsaturated hydrocarbons that contain the C=C double bond functional group and the general formula of CnH2n
Molecular formula for ethene
C2H4
Structural formula for ethene
CH2=CH2
Empirical formula of ethene
CH2
Molecular formula for propene
C3H6
Structural formula for propene
CH2=CH-CH3
Empirical formula for propene
CH2
Molecular formula for Butene
C4H8
Structural formula for butene
CH2=CH-CH2-CH3
Empirical formula for butene
CH2
Word equation for reaction of bromine and alkane in Uv light
Alkane + bromine -(UVlight)—> bromoalkane + hydrogen bromide
Word equation for reaction of chlorine with alkane in UV light
Alkane + Chlorine -(UVLIGHT)—> chloroalkane + hydrogen chloride
What is the name of the type of reaction when alkanes and bromine react under UV light? Why is it called this?
- when alkanes and halogens react, they do a substitution reaction
- this is because a bromine atom takes the place of one hydrogen atom on the alkane and the other bromine atom forms hydrogen bromide with the other hydrogen that the first bromine took the place of
What are the names of the 2 unbranched chain isomers of butene
But-1-ene and but-2-ene
What happens when alkenes react with bromine water?
- alkenes undergo addition reactions
- the C=C double bond breaks and becomes a single bond
- the bromines add onto the 1st and 2nd carbon atoms to produce dibromoalkanes
What is the colour change of the bromine water when alkenes react with it?
Orange to colourless
What is the stem of the product of the addition reaction between bromine water and alkenes?
1,2-dibromo-
What does the 1,2 in front of the dibromoalkane name mean?
Shows that the bromine atoms add onto the 1st and second carbon atoms
Describe the addition reaction of alkenes to become dibromoalkanes
- the alkene is put into a bromine water solution that’s orange in colour
- then the double C=C bond breaks and 2 bromines add onto the first and second carbon atoms
- THE SOLUTION DECOLOURISES FROM ORANGE TO COLOURLESS
- this forms a 1,2-dibromoalkane
What is the name for when the bromine water changes colour when alkenes are added?
- Decolourising
- the bromine water decolourises from orange to colourless when alkenes are added
How can you distinguish between alkenes and alkanes using bromine water?
- when you add alkenes to bromine water, the colour changes from orange to colourless. This is because the bromine molecules break and add onto the alkenes and produces dibromoalkanes
- when you put alkanes into bromine water, nothing happens as they are saturated hydrocarbons and don’t have a C=C double bond like alkenes
3 reasons why cracking is useful
- Provides more short chains alkanes that have more uses such as fuels like gasoline
- Uses up oversupply of less useful, long chain alkanes
- Alkenes are produced = are more reactive + used to make polymers and plastics
What are the effects of acid rain on the environment?
- kills aquatic plant and animal life
- damages trees
- damages limestone buildings
Functional group
An atom or group of atoms responsible for a molecule’s chemical properties
