groups of atoms responsible for the characteristic reactions of a particular compound
naming organic compounds
3 steps:
Find the suffix (dictated by its functional group)
find the prefix (dictated by the number of carbon atoms)
find the position of the functional group
structural isomers
molecules that have the same molecular formula but have a different arrangement of the atoms in space
homologous series
a series of compounds with the same functional group
characteristics of a homologous series
all members of the series can be presented by the same general formula
consecutive members of the series differ by CH2
they have similar chemical properties because they have the same functional group
their physical properties change in a predictable way
Alkanes
end with 'ane'
are saturated hydrocarbons that only have single carbon-carbon bonds
the carbons are attached to hydrogen with single bonds
general formula: CnH2n+2
generally unreactive
undergo combustion and substitution reaction
Petroleum (crude oil) is a complex mixture of hydrocarbons that also contains natural gas
it is a thick, sticky, black liquid found under porous rock (under the ground and sea)
the fractions in petroleum are separated from each other in a process called fractional distillation
the molecules in each fraction have similar properties and boiling points, which depend on the number of carbon atoms in the chain
the boiling point and viscosity of each fraction increase a the carbon chain gets longer
viscosity
the viscosity of a liquid is a description of its resistance to flow or refers to the ease of flow of a liquid.
a viscous liquid like honey flows much more slowly than a non-viscous liquid like ethanol
high-viscosity liquids are thick and flow less easily. With an increase in carbon atom count, the hydrocarbon molecules' attraction to one another also increases, making the liquid more viscous as the hydrocarbon chain lengthens.
the liquid flows less easily with increasing molecular mass
fractional distillation
carried out in a fractioning column, which is hot at the bottom and cools at the top. Crude oil enters the fractioning column and is heated, so vapors rise.
vapors of hydrocarbons with very high b.p. will immediately turn into liquid and are tapped off at the bottom
vapors of hydrocarbons with low b.p. will rise up the column and condense at the top to be tapped off
the different fractions condense at different heights according to their b.p. and are tapped off as liquids
the fractions containing smaller hydrocarbons are collected at the top of the fractioning column as gases
the fractions containing bigger hydrocarbons are collected at the lower sections of the fractioning column
Mnemonic
Refrigerated: refinery gases
Ganglia: gasoline/petrol
Never: Naptha
Knew: kerosense
Dogs: diesel
Feed: fuel oil
Lions: lubricating oil
Butter: bitumen
Viscosity
The liquid flows less easily with increasing molecular mass
As carbon chain length increases
The color of the liquid gets darker as it gets thicker and more viscous
As the molecules get larger
The intermolecular attraction becomes greater. More heat is needed to separate the molecules. With increasing molecular size there is an increase in boiling point
Volatility
The tendency of a substance to vaporize
With increasing molecular size
Hydrocarbon liquids become less volatile because the attraction between the molecules increases
uses of fractions
refinery gas: heating and cooking
gasoline: fuel for cars (petrol)
naphtha: raw product for producing chemicals
kerosene: for making jet fuel (paraffin)
diesel: fuel for diesel engines (gas oil)
fuel oil: fuel for ships and for home heating
lubricating oil: for lubricants, polishes, and waxes
bitumen: for surfacing roads
substitution reaction
one atom (or a groip of atoms) is replaced by another atom (or a group of atoms)
alkanes undergo a substitution reaction with halogens in the presence of ultraviolet light radiation (sunlight is a source of UV radiation), this reaction is called a photochemical reaction.
the UV light provides the activation energy, Ea, for the reaction. A hydrogen atom is replaced with the halogen atom, and more than one hydrogen atom can be substituted depending on the amount of ultraviolet radiation present
In the presence of ultraviolet (UV) radiation, methane reacts with chlorine to form chloromethane and hydrogen chloride
chloromethane: CH4 + Cl2 ---> HCl + CH3Cl
dichloromethane: CH2Cl + Cl2 ---> HCl + CH2Cl2
complete combustion of an alkene
gives carbon dioxide and water
CH4 + 2O2 ---> CO2 + 2H2O
incomplete combustion of an alkene
gives carbon monoxide and water
2CH4 + 3O2 ---> 2CO + 4H2O
Alkenes
end in 'ene'
hydrocarbons
general formula: CnH2n
contain carbon double bonds (C=C)
functional group: carbon-carbon double bond (C=C)
undergo addition reactions and are therefore called unsaturated hydrocarbons
Manufacture of alkenes
alkenes are made by cracking alkanes
large alkane molecules obtained by fractional distillation of petroleum, are passed over a heated catalyst (silicon IV oxide & aluminium oxide)
larger alkanes are broken down into simpler alkanes, alkenes and possibly hydrogen
the C=C double bond in alkenes can be broken to "add" molecules onto the compound
alkenes can undergo addition reactions with bromine, hydrogen and steam
aqueous bromine undergoes addition reactions with alkenes. As a result, the original brown color of aqueous bromine will turn colorless in the presence of alkenes.
each carbon atom of the double bond accepts a bromine atom, causing the bromine solution to lose its color
Hydrogen reacts with alkenes to produce alkenes. These are hydrogenation reactions and occur at
150 degrees
using a nickel catalyst
hydrogenation reactions are used to manufacture margarine from vegetable oils
water can react with alkenes to make alcohols. This type of reaction is called hydration
The conditions required from this reaction are:
temperature of around 300 degrees
pressure of 60-70 atm
concentrated phosphoric acid catalyst
Addition polymerization
polymerization is the formation of long chain molecules called polymers from a large number of smaller monomer molecules
ex. polymers (polystyrene and PVC)
the monomers form repeat units, which are linked by covalent bonds
addition polymers are formed from monomers containing C=C bonds
the C=C bond of the monomer breaks and the monomer forms a single bond with an adjacent monomer
put the monomer name in brackets and add 'poly' in front of the monomer name
to deduce the monomer from the polymer
identify the repeating unit in the polymer
change the single bond in the repeat until to a double bond in the monomer
remove the bond from each end of the repeat unit
to draw the repeat unit
change the double bond to a single bond
add the group from monomer into the correct place
add a bond to each end of the repeat unit
add brackets
write a small "n" in the bottom right hand side
make sure the bonds extend outside the brackets
Alcohols
ends with '-ol'
general formula: CnH2n+1OH
OH is the functional group
Hydration of etheneadvantages
1. No waste products
2. Continuous production
Hydration of ethenedisadvantages
Use of crude oil, which is non-renewable
Requires a lot of energy for high heat and pressures
Fermentation
1. Chemical breakdown of glucose by yeast (or other microorganisms)
2. Producing carbon dioxide and ethanol
3. Reaction catalysed by yeast enzymes
Fermentation reaction
C6H12O6 → 2CO2 + 2C2H5OH
Fermentationadvantages
Renewable (uses plants)
Uses less energy (lower temperature & pressure)
Fermentationdisadvantages
Slow, batch process ie needing new batch once yeast die
Produces carbon dioxide as waste
Ethanol properties & uses
ethanol burns with blue flame. Combustion of ethanol will produce carbon dioxide and water