A series of organic compounds with the same functional group but with each successive member differing by CH2
What is a functional group?
The part of the organic molecule responsible for its chemical reactions
What is a hydrocarbon?
A compound of hydrogen and carbon only
What is a saturated and an unsaturated hydrocarbon?
Saturated: Has single bonds only
Unsaturated: contains a carbon-carbon double bond
Members of the alkane series
Types of compounds
Halogenoalkane F, Cl, Br, I
Carboxylic Acid -COOH
Empirical formula: simplest whole number ratio
Molecular formula: actual number of atoms of each element in a molecule
General formula: simplest algebraic formula e.g. CnH2n+2
Displayed formula: shows relative positioning of all the atoms
Structural formula: shows minimal detail for the arrangement e.g. CH3CH2CH2Br
Skeletal formula: simplified organic formula
What is a structural isomer?
Molecules with the same molecular formula but with different structural arrangements of atoms
What is a stereoisomer?
Compounds with the same structural formula but with a different arrangement of the atoms in space
What is E/Z isomerism?
A type of stereoisomerism in which different groups attached to each carbon of a C=C bond may be arranged differently in space because of restricted rotation of the C=C bond
What is cis-trans isomerism?
A special type of E/Z isomerism in which there is a non-hydrogen group and hydrogen on each C of a C=C bond. Cis, H on same side
Covalent bond fission
Homolytic: the breaking of a covalent bond, with one of the bonded electrons going to each atom, forming two radicals. X-Y -> X. + Y.
Heterolytic: the breaking of a covalent bond with both of the bonded electrons going to one of the atoms. X-Y -> X+ + Y-
What is a nucleophile and electrophile?
Nucleophile: electron pair donor
Electrophile: electron pair acceptor
What is a radical?
A species with an unpaired electron
What is an addition reaction?
A reaction in which a reactant is added to an unsaturated molecule to make a saturated molecule
E.g. Ethene + Bromine -> 1,2-dibromoethane
What is a substitution reaction?
A reaction in which an atom or group of atoms is replaced with a different atom or group of atoms
E.g. Bromoethane + OH- -> Ethanol + Br-
Mixture of over 150 different hydrocarbons
Fractional distillation: the separation of the components in a liquid mixture into fractions which differ in boiling points
Boiling points of alkanes
Chain length: increasing chain length, increases boiling point, more van der Waals' forces between the molecules in longer chains, takes more energy to separate them
Branching: same molecular mass, unbranched molecules have a higher boiling point, more points of contact for van der Waals' forces
Combustion of alkanes
burning in a plentiful supply of oxygen
carbon dioxide and water is formed
burning in a limited supply of oxygen
such as in an internal combustion engine
carbon monoxide is formed
the breaking down of long-chained saturated hydrocarbons to form a mixture of shorter-chained alkanes and alkenes
catalytic cracking: uses a zeolite catalyst at about 450 degrees
many different possible equations for cracking
Branched alkanes: unbranched alkanes can be converted into branched alkanes using isomerisation
Cyclic hydrocarbons: reforming, alphatic hydrocarbons being converted into cyclic or aromatic hydrocarbons
Radical substitution of alkanes
a type of substitution reaction in which a radical replaces a different atom or group of atoms
UV radiation needs to be present
covalent bonds are broken by homolytc fission to form radicals with an unpaired electron
Mechanism: initiation, propagation, termination
Limitations: mixture of products are formed
alkenes and cycloalkenes are unsaturated hydrocarbons (have atleast one C=C double bond)
General formula: CnH2n
Double bond in alkenes
made up from a sigma bond and a pi bond
Formation of the double bond: sigma bond is formed between two carbon atoms by the overlap of orbitals, a pi bond is formed above and below the plane of the carbon atoms by sideways overlap off p-orbitals, the pi bond fixes the carbon atoms in place
pi-bond prevents rotation of the bond
Shape of an alkene molecule
3 regions of electron density around each carbon atom in the double bond
the pairs of electrons repel each other as far apart as possible to minimise repulsions
trigonal planar shape: bond angles 120 degrees
ethane is a flat planar molecule
Addition reactons of alkenes
Hydrogenation: addition of hydrogen gas, catalyst of nickel, temperature 150oC
Halogenation: addition of halogens, room temperature
Test for unsaturation: adding bromine to a sample, if it contains an alkene the colour changes from orange to colourless
Addition reaction of alkenes with hydrogen halides