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What is a homologous series?
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
- 1. Methane
- 2. Ethane
- 3. Propane
- 4. Butane
- 5. Pentane
- 6. Hexane
- 7. Heptane
- 8. Octane
- 9. Nonane
- 10. Decane
Types of compounds
- Alkane C-C
- Alkene C=C
- Halogenoalkane F, Cl, Br, I
- Alcohol -OH
- Aldehyde -CHO
- Ketone C-CO-C
- 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
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 reaction of alkenes with hydrogen halides
- produing a halogenoalkane
- Unsymetrical alkenes:
Addition reaction with steam
- hydration of an alkene
- high temperature and pressure
- phosphoric acid catalyst
Electrophilic addition in alkenes
- Electrophile: electron pair acceptor
- Curly arror: movement of an electron pair