C7: Organic chemistry Flashcards
what is crude oil? is it finite?
- a mixture of compounds
- a fossil fuel consisting of the remains of ancient biomass
- finite resource - cannot be replaced as it is used up
What is a hydrocarbon?
- a compound made up exclusively of hydrogen and carbon atoms
What are alkanes and their formula?
Saturated hydrocarbons of a general formula
CₙH₂ₙ₊₂
what is a homologous series ?
- Series of compounds with the same:
- general formula,
- functional groups
- and similar chemical properties
Describe the combustion of hydrocarbons
- exothermic reaction occurs when hydrocarbons are reacted with oxygen
- complete combustion produces carbon dioxide and water ( carbon and hydrogen atoms are completely oxidised
- incomplete combustion produces carbon or carbon monoxide and water
Describe the 3 physical properties of alkanes
- boiling points and viscosity increase as molecules get bigger
- volatility and flammability decrease as molecules get bigger
- poor reactivity
define ‘cracking’?
when large hydrocarbons are thermally broken down into smaller and useful molecules
What type of reaction is cracking?
Thermal decomposition
what are the two types of cracking ?
- catalytic cracking: reactant heated to vapour passed over a hot catalyst
- steam cracking: heated to vapour , mixed with steam and heated to high temperatures
How are the products of cracking used?
The products are alkanes and alkenes
- used as polymers and starting materials for synthesis
Explain how fractional distillation of crude oil takes place
- Crude oil is heated and vapourised
- vapour rises up the fractionating column
- the column is hotter at the bottom and cooler at the top
- Hydrocarbons cool as they go up the column and condense at different heights, as they have different boiling points
- large molecules , high boiling points - at bottom
- small molecules , low boiling points - at the top
What is an alkene
- unsaturated hydrocarbon
- contains a C=C bond
- general formula for alkenes is CₙH₂ₙ
What is the test for alkenes?
- Add bromine water
- Colour change occurs from orange to colourless
Describe the combustion of alkenes
- they burn with smoky flames due to incomplete combustion
What are the reaction conditions for
addition polymerisation?
●High temperature
● High pressure
● Titanium catalyst
State the differences
between addition and condensation polymerisation
- In addition polymerisation, only one product is formed whereas in condensation polymerisation two different products are formed (the polymer and a small molecule)
- Condensation polymerisation involves
monomers with 2 different functional group
whereas addition polymerisation involves just 1
functional group
Describe the three addition reactions of alkenes and their requirements
- with hydrogen: hydrogenation ; requires a higher temperature and a nickel catalyst
- with steam - hydration ; requires high temperature, pressure and concentrated phosphoric acid as a catalyst
- With Br₂/Cl₂/I₂ - addition of halogens
What is an alcohol?
- an organic compound that contains an -OH functional group
State the names and chemical formulae of
the first 4 members of the homologous series
of alcohols
● Methanol (CH₃OH)
● Ethanol (C₂H₅OH)
● Propanol (C₃H₇OH)
● Butanol (C₄H₉OH
State the structural formula for the first 4
members of the homologous series of
alcohols
● Methanol – CH₃OH
● Ethanol – CH₃CH₂OH
● Propanol – CH₃CH₂CH₂OH
● Butanol – CH₃CH₂CH₂CH₂OH
State characteristics of the first 4 alcohols
- dissolve in water to form a neutral solution
- react with sodium to form hydrogen and sodium ( ethoxide eg)
- burn in oxygen
- react with carboxylic acids in presence of acid catalyst to form esters
What happens when
an alcohol reacts with an
oxidising reagent?
A carboxylic acid is produced
State 3 uses of alcohols
● Solvents
● Alcoholic drinks
● Fuels
State the conditions required for fermentation of glucose and state the equation of the reaction
- 30℃
- aqueous solution of the glucose
- absence of air
- yeast added
C₆H₁₂O₆ → 2C₂H5OH + 2CO₂