Organic chemistry Flashcards
how is crude oil formed
- crude oil is a finite resource
- it is found in rocks
-is formed over millions of years from the remains of the tiny sea creatures ( plankton) which were buried in mud
what is a homologous series
group of organic compounds that have similar chemical properties, due to them having the same functional group.
what is an alkane
a homologous series of hydrocarbons that contain hydrogen and carbon atoms with no double bonds
what are the molecules that we find in crude oil
- crude oil is a mixture of hydrocarbons
- a hydrocarbon found in crude oil is methane
-another hydrocarbon found in crude oil is ethane
what is the formula of methane hydrocarbon
CH4
what is a hydrocarbon
molecules made up of only hydrogen and carbon atoms only
what is the formula for the alkane ethane
C2H6
what is the general formula for alkanes
CnH2n+2
what type of molecules are alkanes
saturated - because every carbon atoms have 4 single covalent bonds (no double bonds )
what are the first 4 members of the alkanes
methane, ethane, propane, butane
what are the properties of the hydrocarbon
- viscosity
- flammibility
-boiling point
what does viscosity mean and how does it affect hydrocarbons
-tells us the thickness of a fluid ( fluids with high viscosity flow slowly)
- as the size of the hydrocarbon molecule increases ( As you go down the 4 members of alkanes ), the molecules get more viscous ( LONG CHAIN HYDROCARBONS ARE EXTREMELY VISCOUS )
what does flammability mean and how does it affect hydrocarbons
flammability - tells us how easily a hydrocarbon combusts
- short chain hydrocarbons are extremely flammable
- as the size of the hydrocarbon increases the flammability of the molecules decreases and LONG CHAIN HYDROCARBONS ARE DIFFICULT TO BURN
what does boiling point mean and how does it affect hydrocarbons
the temperature at which a liquid turns to a gas
- Short-chain hydrocarbons have low boiling points - all of the first 4 hydrocarbons in the alkanes are gases at room temperature because they have boiling points which are lower than room temperature
- as the size of the hydrocarbon molecule increases, the boiling point also increases - very long hydrocarbons have very high boiling points
what happens when hydrocarbon fuels are combusted
they release energy
describe the combustion of hydrocarbon
- during combustion, the carbon and hydrogen atoms in the fuel react with oxygen and the carbon and hydrogen are oxidised
- if the oxygen is unlimited ( complete combustion reactions ) the reaction produces carbon dioxide and water
explain how fractional distillation of crude oil takes place
- crude oil is heated to very high temperatures = causing crude oil to boil and so all the hydrocarbons evaporate and turn to gas
- crude oil vapour is fed into the fractional distillation column
- the column is hotter at the bottom and cooler at the top
- the hydrocarbon vapours now rise up in the column
-the hydrocarbons will condense when they reach their boiling point and the liquid fractions are then removed - the remaining hydrocarbons continue moving up the column
-these will condense when they reach their boiling point - very long hydrocarbons have very high boiling points so they are removed from the bottom of the column
- short hydrocarbon chains have very low boiling points, these dont condense and they are removed from the top of the column as gases
what are some examples of fractions being used as fuels
- petrol and diesel ( for cars ) , kerosene ( jet fuel ) , heavy fuel oil( for ships) , liquified petroleum gas ( camping stoves)
what are some other uses of fractions
used as feedstocks for petrochemical industry
what is a feedstock
a chemical that is used to make other chemicals
what are examples of usage of feedstock fractions
- solvents
-lubricant
-detergents
-polymers
what are some features of alkanes
- have general formula CnH2n+2
- only have a single covalent bond between the carbon atoms
how do you change a long chain hydrocarbon into a short chain hydrocarbon
by cracking
describe the conditions needed for cracking
two ways:
catalytic cracking - high temperatures and catalysts are used - the catalyst will speed up the reaction without being used
steam cracking: high temperature and steam is used
what is an alkene
unsaturated hydrocarbon with double covalent bond between 2 carbon atoms
- useful molecules that are used to make polymers
- more reactive than alkanes
describe the test for alkenes
- test using bromine water ( which is orange)
- if shake the alkene with bromine water then the bromine water will turn colourless
what is the general formula for the alkenes
CnH2n
why are alkene molecules unsaturated
because alkenes have 2 fewer hydrogen atoms than an alkane but both have the same number of carbon atoms
describe the combustion of alkenes
- when we combust alkenes the product is carbon dioxide and water AND unburnt carbon particles ( this is because of incomplete combustion) - this means that alkenes burn in air with a smoky flame
describe the reactions and conditions for the addition of hydrogen
process name = hydrogenation
- hydrogenation process requires a temperature of approximately 150 degrees
- a nickel catalyst is also needed to speed up the reaction
- in this reaction the two hydrogen atoms add across the double bond and the double carbon bond is converted into a carbon to carbon single bond
- reacting the alkene with hydrogen produces an alkane
what does the addition reaction of an alkene with hydrogen, water and halogen produce
an alkane
what is the functional group of the alkenes
the double bond
describe how alkenes react with
water and the conditions needed
process name: hydration
the reaction is reversible so to increase the yield of the reactant you can pass any unreacted reactants back through the catalyst BUT it requires high temperature therefore lots of energy is required
- the water must be in the form of steam
- the temperature must be around 300 degrees
- the pressure must be around 70 atmospheres
- phosphoric acid is used as the catalyst to speed the reaction
describe how alkenes react with
halogens
alkenes react rapidly with halogens
the product make a di ———-
eg ethene + bromine –> DIbromoethANE
what are some uses of alchohols
fuels
solvents
alcoholic drinks
what is the alcohol functional group
OH
what are the ways to make ethenol AND THE CONDITIONS NEEDED AND ADVANTAGES AND DISADVANTAGES
fermentation starts with a sugar solution ( glucose ) and mix with yeast which converts the sugar solution to a solution of ethanol and carbon dioxide is also produced
CONDITIONS:
-the temperature should be around 30 degrees
- the reaction must take place in anaerobic conditions
ADVANTAGES of reacting with fermentation:
- the low temperature means that the reaction doesn’t require lots of energy
- the sugar for this reaction comes from plants = it is renewable
DISADVANTAGE:
-the product is an aqueous solution of ethanol - so the ethanol needs to be purified by distillation which requires energy
hydration of ethene -
ADVANTAGE:
- produces a high yield of ethenol
DISADVANTGE :
- requires lots of heat = lots of energy required
what is the solubility of alcohols in water
alcohols are soluble in water and form neutral solutions
BUT as the number of carbon atoms increase, the solubility decreases
what happens when ethanol reacts with sodium
- see bubbles of hydrogen gas being produced
ethanol + sodium -> sodium ethoxide + hydrogen
how does methanol react with sodium
methanol + sodium -> sodium methoxide + hydrogen
how does propanol react with sodium
propanol + sodium -> sodium propoxide + hydrogen
how does butanol react with sodium
butanol + sodium -> sodium butoxide + hydrogen
what is the product when an alcohol reacts with an oxidising agent
carboxylic acid and water
how does ethanol react with an oxidising agent
ethanol + oxidising agent-> ethanoic acid + water
how does methanol react with an oxidising agent
methanol + oxidising agent -> methanoic aid + water
how does propanol react with an oxidising agent
propanol + oxidising agent -> propanoic acid + water
how does butanol react with an oxidising agent
butanol + oxidising agent -> butanoic acid + water
what do alchohols release when combusted
energy
what is the product of combusting an alchohol in air
produces carbon dioxide and water
