Organic Chemistry Flashcards
Crude oil
Remains of ancient biomass consisting mainly of plankton
Hydrocarbons
Molecules made up of carbon and hydrogen only
About alkanes
- CnH2n+2
- MEPB (methane, ethane…)
- saturated hydrocarbons (molecules with only single bonds between C atoms)
Fractional distillation
Evaporation:
- Crude oil is heated until it evaporates.
- Crude oil vapour is put into a fractionating column at the bottom and rises upwards
Condensation:
- The temperature is highest at the bottom of the column. Long-chain hydrocarbons condense at the bottom and are collected as liquids.
- Short-chain hydrocarbons have lower boiling points -> they pass up the column and condense at lower temperatures nearer the top
Petrochemicals
The fractions in fractional distillation can be processed to produce fuel and feedstock for the petrochemical industry
-> eg kerosene
Properties of hydrocarbons
- the shorter the molecules the less viscous
- the shorter the lower its boiling point
- the shorter the more flammable
The 2 cracking processes of hydrocarbons
- Passing them over a hot catalyst (catalytic cracking)
- Mixing them with steam and heating to very high temperatures -> so that thermal decomposition can occur (steam cracking)
Alkenes
- CnH2n
- unsaturated (have at least one carbon double bond)
- first 4 are ethene, propane, butene and pentene
Test for alkenes
React with bromine water to turn it from orange to colourless
Why don’t alkanes react with bromine water
Because it doesn’t have a double bond like alkene which makes alkenes more reactive
Why are products of cracking useful as fuels
They have shorter chains than the original alkanes making them more flammable
Alkenes reactions
With oxygen:
- burn in air with smoky flames because of incomplete combustion (C or CO is formed)
also react with halogens, water and hydrogen
- the double bond breaks and joins with the new reactant
Alkenes with halogens, water and hydrogen (hydration, hydrogenation, halogenation)
- the C=C breaks to form a C-C bond
- the added compounds splits in 2 and are added to either of the Cs
- H2O splits into H and OH, H2 splits into 2 Hs and Br2 splits into 2 Brs
What is the alcohol functional group
-OH
The first 4 alcohols and their letter symbols
Methanol -> CH3OH
Ethanol -> C2H5OH
Propanol -> C3H7OH
Butanol -> C4H9OH
Reactions of alcohols
ignite ethanol:
- burn to produce carbon dioxide and water
- burns easily with blue flame
add water to universal indicator:
- dissolve to form a neutral solution (pH 7)
with sodium:
- bubbles/fizzing
- to produce hydrogen and a salt
warm with acidified sodium dichromate solution:
- sodium dichromate turns orange from green
Uses of alcohols
- methanol: chemical feedstock
- ethanol: alcoholic drinks
- fuel
Hydrogenation
Alkene + hydrogen → alkane
-> needs a catalyst
Hydration
Alkene + water (steam) → alcohol
-> needs hot temperatures and a catalyst
Halogenation
Alkene + halogen → halogenoalkane
2 ways of preparing ethanol
- Fermentation
- Hydration of ethene with steam
What is the functional group of carboxylic acids
-COOH
Letter symbols for the first few carboxylic acids
Methanoic acid -> CHOOH
Ethanoic acid -> CH3COOH
Propanoic acid -> C2H5COOH
Butanoic acid -> C3H7COOH
Reactions of carboxylic acids
with water:
- dissolve in water to produce acidic solutions
with metal carbonates:
- produce carbon dioxide, water, salt
with alcohols:
- to produce esters (needs an acid catalyst)
What does ethanol and ethanoic acid make
Ethyl ethanoate